WO2020128644A1

WO2020128644A1 - A process for bio-transformation and production of d-lactones thereof

Info

Publication number: WO2020128644A1
Application number: PCT/IB2019/051024
Authority: WO
Inventors: Archana BHAT; Anuradha Mukherjee; Jonathan Mark Bonello; Nimitha Korrapati; Ajit KUMAR SATAPATHY
Original assignee: Tojo Vikas Biotech Pvt. Ltd.
Priority date: 2018-12-18
Filing date: 2019-02-08
Publication date: 2020-06-25

Abstract

The present disclosure provides a process for converting unsaturated lactones to their saturated counterparts through a process of biotransformation. More specifically, the present disclosure relates to a process that employs a reductase-dehydrogenase coupled reaction to bio-transform unsaturated lactones to saturated δ-lactones. The process involves reduction of the said unsaturated lactones, which is facilitated by presence of a cofactor and co-substrate, that participate in the said coupled reaction. The process of the present disclosure not only increases the conversion of the unsaturated lactone to saturated lactone but also increases the yield of the said saturated lactone.

Description

A PROCESS FOR BIO-TRANSFORMATION AND PRODUCTION OF d-LACTONES THEREOF

TECHNICAL FIELD

The present disclosure generally relates to field of bio-transformation, and more specifically to microbial biotransformation of unsaturated chemical compounds to their saturated forms. Particularly, the present disclosure provides a process of bio-transformation to convert an unsaturated lactone by reduction, to its saturated form. The process involves presence of a co-substrate and a cofactor, which participate in the biotransformation process through a reductase-dehydrogenase coupled reaction, thereby making the process more efficient and increasing the yield of the saturated lactone. The bio-transformation is facilitated by the presence of a microorganism or by the presence of enzymes produced by the microorganism.

BACKGROUND OF THE DISCLOSURE

Lactones are cyclic esters of hydroxycarboxylic acids, containing a 1- oxacycloalkan-2-one structure, or analogues having unsaturation or heteroatoms replacing one or more carbon atoms of the ring. Lactones are formed by intramolecular esterification of the corresponding hydroxycarboxylic acids, which takes place spontaneously when the ring that is formed is five- or six-membered. Naturally occurring lactones are mainly unsaturated lactones which are intramolecular esters of the corresponding hydroxy fatty acids. They contribute to the aroma of fruits, butter, cheese, and other foods.

One such source of naturally occurring lactone is Cryptocaria massoia or Massoia tree. Massoia is a tropical tree native to Papua New Guinea. This medium-sized tree grows in rain-forests at 400 m to 1000 m altitude. The bark of the tree is aromatic and has a pleasant sweet, coconut-like flavour. The bark is used for production of massoia bark oil.

The lactone obtained from the massoia tree or the‘massoia lactone’ is an alkyl lactone derived from the bark of the massoia tree, though the compound can also be found as a component of cane sugar molasses, cured tobacco, and the essential oil of Sweet Osmanthus ( Osmanthus fragrans). Known in the late 18^th and early 19^th centuries as massoy bark, massoia essential oil was once widely used as a natural coconut flavouring.

Massoia lactone has an odour that is described as sweet, coconut, lactonic, creamy, milky and waxy and, at a dilution of 20 ppm, a taste described as creamy, coconut, green, and slightly fruity. The massoia lactones are 10, 12 and 14 carbon chain compounds, that possess characteristic a, b-unsaturated d-lactone moieties They also present substitution at the C6 position of the a, b-unsaturated d-lactone structures with chains of variable length containing five, seven or nine carbons. Massoia bark oil typically consists of 69% C-10 lactones, 8% C-12 lactones, 3% terpenes, 2% of d-decalactone, 4% of benzyl benzoate and nearly 14% unidentified materials.

While most of the lactones present in massoia are unsaturated, the corresponding saturated lactones, such as d-decalactone or d-dodecalactone, have not been reported to be manufactured from the massoia source efficiently and in high yields, either starting from its bark extract or oil. As these saturated d-lactones are known to be flavour compounds, for example d-decalactone having a strong, sweet, creamlike or nutlike fragrance, and have conventionally been used as ingredient for the preparation of flavour compositions, their preparation is desired.

Currently existing literature suggests several alternatives for preparation of d- decalactone or d-dodecalactone, by methods such as hydrogenation or microbial fermentation/reduction by using bacterium from a variety of different species, including Clostridium, Saccharomyces, Pseudomonas, Bacillus, Proteus, Cellulomonas, Micrococcus, Xanthomonas and Acetobacter species, to obtain d- decalactone and d-dodecalactone from the corresponding unsaturated starting materials. Use of novel paralog genes of hemiascomycetes yeasts for the production of g and d lactones has also been explored.

Further, production of d-decalactone (and d-dodecalactone) have also been shown from 11-hydroxypalmitic acid (and ethyl 11-hydroxypalmitate) by culturing Candida sorbophila, or from linoleic acid and hydrolysed com oil using a culture belonging to Pediococcous or Bifidobacterium species; or from 11 -hydroxy palmitic acid and other vegetable fats such as margarine and cooking oils by employing Saccharomyces cerevisiae.

Additionally, production of d-decalactone by bioconversion of linoleic acid using a hydratase enzyme is also reported. Further, lactones are also known to be acid catalysed from chiral hydroxy acids/esters which are formed from reduction of g- and d-keto acids/esters.

However, none of the methods employ natural sources of unsaturated lactones to convert them to their saturated counterparts, using microbial transformation or products thereof. This is important because in recent years, there is a growing tendency to use natural materials for the manufacture of food and cosmetic additives including flavours and perfumes. Consequently, it is strongly desired in the field of the flavour industry to develop flavours obtainable without use of chemical synthesis techniques, such as natural flavours harvested from natural source materials, and flavours produced by biotransformation using enzymes. Further, it is also frequently desirable to identify these flavour components as being “natural flavours”, thereby playing an important role in the commercialization of products containing them.

Since a flavour compound prepared by biotransformation using naturally sourced ingredients can be designated as a natural product, there is a demand to develop methods to produce flavouring components and, in particular, for the production of lactones which can be qualified as “natural”. In addition, d-decalactone produced by chemical synthesis techniques lack a naturally mild creamlike scent or flavour and is not always satisfactory when used as an ingredient for the preparation of flavour compositions. Thus, there exists a need to utilize natural sources of unsaturated lactones and covert them to saturated lactones by methods that involve non-synthetic means, are efficient, yield sufficient quantities of the desired product and are suitable for practical purposes.

SUMMARY OF THE DISCLOSURE The present disclosure relates to a process for bio-transforming an unsaturated lactone to produce a saturated lactone, said process comprising reduction of said unsaturated lactone in the presence of a reductase-dehydrogenase coupled reaction, wherein the reduction is facilitated by hydrogenation of the unsaturated lactone by a reduced cofactor.

In embodiments of the present disclosure, the unsaturated lactone is selected from a group comprising 2-decen-5-olide, 2-dodecen-5-olide and 2-tetradecen-5-olide or any combination thereof; and wherein the bio-transformation results in a corresponding saturated d-lactone selected from a group comprising 5-decanolide, 5-dodecanolide and 5-tetradecanolide, respectively.

In embodiments of the present disclosure, the unsaturated lactone is a massoia lactone.

In embodiments of the present disclosure, the reductase and dehydrogenase enzymes employed in the present disclosure are enoate reductase (ERED) and glucose dehydrogenase (GDH), respectively. While the reductase participates in conversion of unsaturated lactone to saturated d-lactone, the dehydrogenase oxidizes a co-substrate, glucose, and in the process reduces the cofactor.

In embodiments of the present disclosure, the cofactor is Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP). The present disclosure accordingly also provides a codon optimized sequence of enoate reductase (ERED) and glucose dehydrogenase (GDH) as set forth in Sequence ID Nos. 1 and 2, respectively.

In embodiments of the present disclosure, these sequences, individually or in combination, are cloned into a vector, which is used to transform a host cell that carries out the biotransformation reaction that converts the unsaturated lactone to produce the saturated lactone. Accordingly, the host may comprise one or two vectors, comprising sequences for ERED or GDH or both. Alternatively, the biotransformation reaction is carried out in presence of the ERED and GDH enzymes produced by the host cell. In embodiments of the present disclosure, these host cells or the enzymes produced by them are employed in a reaction mixture, along with the unsaturated lactone or a source thereof, such as massoia bark oil, the oxidized cofactor, the co substrate and a buffer for the bio-transformation to occur via the coupled reaction mechanism.

In embodiments of the present disclosure, the reductase -dehydrogenase coupled reaction converts at least 10% of the unsaturated lactone to saturated lactone; and the reductase-dehydrogenase coupled reaction increases the yield of saturated lactone by at least 50% when compared to a process for conversion of unsaturated lactone to saturated lactone without the coupled reaction.

The present disclosure also provides a flavouring agent comprising the saturated lactone produced from unsaturated lactone by the reductase-dehydrogenase coupled bio-transformation process of as described above.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES In order that the disclosure may be readily understood and put into practical effect, reference will now be made to exemplary embodiments as illustrated with reference to the accompanying figures. The figures together with a detailed description below, are incorporated in and form part of the specification, and serve to further illustrate the embodiments and explain various principles and advantages, in accordance with the present disclosure wherein:

Figure 1 depicts the reductase-dehydrogenase coupled reaction of the present disclosure.

Figure 2 depicts the vectors prepared in the instant disclosure (a) pMALc5x:ERED; and (b) pMALc5x:GDH, respectively. Figure 3 depicts the SDS-PAGE separation of the proteins profile of E.coli cells producing ERED, GDH and both proteins together (marked with arrows). Figure 4 depicts conversion of C-10 massoia lactone to d-decalactone with increase in reaction time, and the conversion of about 94% at the 20th hour of reaction.

BRTFF DESCRIPTION OF THE ACCOMPANYING SEQUENCE LISTINGS

Sequence Id. No. 1 depicts the codon optimized nucleic sequence of ERED of the present disclosure.

Sequence Id. No. 2 depicts the codon optimized nucleic acid sequence of GDH of the present disclosure.

Sequence Id. No. 3 depicts the native nucleic sequence of ERED obtained from Bacillus subtilis.

Sequence Id. No. 4 depicts the native nucleic sequence of GDH obtained from Bacillus subtilis.

DETAILED DESCRIPTION OF THE DISCLOSURE

In view of the drawbacks associated, and to remedy the need created by the available art in the field of technology related to production of d-lactones, the present disclosure aims to provide a process of producing d-saturated lactone from its unsaturated counterpart. More specifically, the present disclosure provides a process for bio-transforming an unsaturated lactone to produce a corresponding saturated lactone in the presence of a reductase-dehydrogenase coupled reaction.

However, before describing the process in greater detail, it is important to take note of the common terms and phrases that are employed throughout the instant disclosure for better understanding of the technology provided herein.

Throughout the present disclosure, the term‘d-lactone’ or‘delta-lactone’ refers to a lactone having an alkyl chain (also known as an alkyl lactone) attached to it at its d (delta) position. As well understood in the field of organic chemistry, the d (delta) position is determined with respect to the positioning of the carbonyl group of the lactone. The said alkyl chain is preferably of 5, 7 or 9 carbon atoms. This term is employed broadly to comprise saturated as well as unsaturated forms of the lactone.

Throughout the present disclosure, the term‘unsaturated’ used in relation to a lactone refers to a lactone comprising a double bound between a (alpha) and b (beta) positions within the lactone ring. The said lactone is therefore an a, b- unsaturated lactone and may further comprise the above stated alkyl chain substitution at d (delta) position and therefore be an a, b-unsaturated d-lactone.

Throughout the present disclosure, the a, b-unsaturated d-lactone comprising an alkyl chain of 5 carbon atoms at the said d (delta) position is intended to cover a compound which may be known by any of its IUPAC or commonly referred names, including but not limited to 6-pentyl-5,6-dihydro-2H-pyran-2-one; dec-2- en-5-olide; 2-decen-5-olide; or 5 -hydroxy-2 -decenoic acid lactone; and also represented by I below:

Throughout the present disclosure, the a, b-unsaturated d-lactone comprising an alkyl chain of 7 carbon atoms at the said d (delta) position is intended to cover a compound which may be known by any of its IUPAC or commonly referred names, including but not limited to 6-heptyl-5,6-dihydro-2H-pyran-2-one; dodec- 2-en-5-olide; 2-dodecen-5-olide; or 5 -hydroxy-2 -dodecenoic acid lactone; and also represented by II below:

II

Throughout the present disclosure, the a, b-unsaturated d-lactone comprising an alkyl chain of 9 carbon atoms at the said d (delta) position is intended to cover a compound which may be known by any of its IUPAC or commonly referred names, including but not limited to 6-nonyl-3,4,5,6-tetrahydro-2H-pyam-2-one; tetradec-2-en-5-olide; 2-tetradecen-5-olide; or tetrahydro-6-nonyl-2H-pyran-2- one; or 5-tetradecanolide

Throughout the present disclosure, the term‘massoia lactone’ refers to an a, b- unsaturated d-lactone, comprising an alkyl chain of 5, 7 or 9 carbon atoms, at the said d (delta) position. The‘massoia lactone’ may therefore also be commonly identified with respect to the total number of carbon atoms present, and accordingly are referred to as C-10 massoia lactone, C-12 massoia lactone or C-14 massoia lactone, respectively. The massoia lactone may be obtained from the bark (or oil thereof) of Cryptocaria massoia or Massoia tree or are prepared synthetically or are procured from commercial sources.

Throughout the present disclosure, the term ‘saturated’ used in relation to a lactone refers to a lactone comprising no double bounds within the lactone ring. The said lactone is therefore a saturated lactone and may further comprise the above stated alkyl chain substitution at d (delta) position and therefore be a saturated d-lactone.

Throughout the present disclosure, the saturated d-lactone comprising an alkyl chain of 5 carbon atoms at the said d (delta) position is intended to cover a compound which may be known by any of its IUPAC or commonly referred names, including but not limited to 6-pentyltetrahydro-2H-pyran-2-one; tetrahydro-6-pentyl-2H-pyran-2-one; (±)-6-pentyltetrahydro-2H-pyran-2-one; 1,5- decanolide; d-decanolactone; (±)-b-pcntyl-d-valcrolactonc: (±)-5-decanolide; or 5- hydroxydecanoic acid d-lactone. Throughout the present disclosure, the saturated d-lactone comprising an alkyl chain of 7 carbon atoms at the said d (delta) position is intended to cover a compound which may be known by any of its IUPAC or commonly referred names, including but not limited to 6-heptyltetrahydro-2H-pyran-2-one; tetrahydro-6-heptyl-2H-pyran-2-one; (±)-6-heptyltetrahydro-2H-pyran-2-one; 1,5- dodecanolide; d-dodecanolactone; (±)-5-heptyl-5-valerolactone; (±)-5- dodecanolide; or 5 -hydroxy dodecanoic acid d-lactone.

Throughout the present disclosure, the saturated d-lactone comprising an alkyl chain of 9 carbon atoms at the said d (delta) position is intended to cover a compound which may be known by any of its IUPAC or commonly referred names, including but not limited to 6-nonyltetrahydro-2H-pyran-2-one; tetrahydro-6-nonyl-2H-pyran-2-one; (±)-6-nonyltetrahydro-2H-pyran-2-one; 1,5- tetradecanolide; d-tetradecano lactone; (±)-d-nonyl-d-valcrolactonc: (±)-5- tetradecanolide; or 5-hydroxytetradecanoic acid d-lactone.

Throughout the present disclosure, the term ‘bio-transformation’ or ‘biotransformation’ or ‘bio transformation’ is used interchangeably and is intended to convey the ordinary conventional meaning of the term known to a person skilled in the art, which generally corresponds to a chemical modification (or modifications) made by an organism on a chemical compound. Biotransformation is thus ordinarily a process by which organic compounds are transformed from one form to another, aided by microorganisms. The term herein also includes said modification of a chemical compound by products, including proteins and enzymes, produced by the said organism. Thus, for biotransformation to take place, presence of the organism is not mandatory, as long as the products, including proteins and enzymes, produced by the said organism are present for the said chemical modification.

Throughout the present disclosure, the phrase‘reductase-dehydrogenase coupled reaction’ or‘coupled reaction’ is used interchangeably and is meant to refer to a set of two reactions, wherein one reaction involves at least one reductase enzyme and the other reaction involves at least one dehydrogenase enzyme. The phrase is intended to convey the ordinary conventional meaning of the term‘coupled’ with respect to a chemical reaction, known to a person skilled in the art, which generally corresponds to a set of reactions where energy required by one process is supplied by another process. A coupled reaction is therefore a chemical reaction having a common intermediate in which energy is transferred from one side of the reaction to the other.

Throughout the present disclosure, the term‘reduction’ used with respect to a chemical entity is intended to convey the ordinary conventional meaning of the term with respect to a chemical reaction, known to a person skilled in the art, which generally corresponds to a chemical reaction that involves the gaining of electrons by one of the atoms involved in the reaction. The term ‘reduced’ therefore refers to the element that accepts electrons, as the oxidation state of the element that gains electrons is lowered. With respect to hydrogen and oxygen, the term‘reduction’ refers to a chemical reaction in which hydrogen is added to, or oxygen is removed from, a compound. The said compound is therefore also termed as’reduced’ when hydrogen is added to it, or oxygen is removed from it. When used in conjunction with microbial processes, the term ‘microbial reduction’ refers to a reaction where‘reduction’ is aided by a microorganism.

Throughout the present disclosure, the term‘oxidation’ used with respect to a chemical entity is intended to convey the ordinary conventional meaning of the term with respect to a chemical reaction, known to a person skilled in the art, which generally corresponds to a chemical reaction that involves movement of electrons away from one of the atoms involved in the reaction. The term ‘oxidized’ therefore refers to the element that donates or loses electrons, as the oxidation state of the element that donates electrons is increased. With respect to hydrogen and oxygen, the term‘oxidation’ refers to a chemical reaction in which hydrogen is removed from, or oxygen is added to, a compound. The said compound is therefore also termed as’oxidized’ when hydrogen is removed from it, or oxygen is added to it.

Throughout the present disclosure, the term‘hydrogenation’ is used to convey the ordinary conventional meaning of the term with respect to a chemical reaction, known to a person skilled in the art, which generally corresponds to a chemical reaction between molecular hydrogen (Tk) and another compound or element. Hydrogenation is therefore typically used to reduce a compound or element and constitutes the addition of pairs of hydrogen atoms to a molecule. With respect to organic compounds, hydrogenation leads to reduction or saturation of organic compounds.

Throughout the present disclosure, the term ‘cofactor’ or ‘co-factor’ is used interchangeably and is used to convey the ordinary conventional meaning of the term known to a person skilled in the art, which generally corresponds to a non protein chemical compound or metallic ion that is required for an enzyme's activity.

As used throughout the present disclosure, the phrase ‘cosubstrate’ or ‘co substrate’ is used interchangeably and is used to convey the ordinary conventional meaning of the term known to a person skilled in the art, which generally refers to an organic substance that reversibly combines to form an active enzyme system and often used for cofactor regeneration to yield greater productivity and lower environmental impact. The term also implies a secondary substrate that forms part of a multi-substrate reaction, including a coupled reaction, wherein the co substrate aids in achieving the chemical objective of the main substrate by participating in reaction and contributing via exchange of electrons or elements.

With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations may be expressly set forth herein for sake of clarity.

The use of the expression“at least” or“at least one” suggests the use of one or more elements or ingredients or quantities, as the use may be in the embodiment of the disclosure to achieve one or more of the desired objects or results.

Throughout this specification, the word “comprise”, or variations such as “comprises” or“comprising” wherever used, will be understood to imply the inclusion of a stated element, integer or step, or group of elements, integers or steps, but not the exclusion of any other element, integer or step, or group of elements, integers or steps.

Accordingly, to reiterate, the present disclosure relates to a process for converting unsaturated lactone to produce a saturated lactone, where the said process is aided by microorganisms or products thereof. The process of the present disclosure is therefore a bio-transformation process that is carried out by a microorganism or enzymes produced by the microorganism that is capable of aiding the said conversion. The bio-transformation process of the present disclosure is carried out in presence of a coupled reaction, which involves participation of a cofactor and a co-substrate. While the co-substrate participates in a chemical reaction to convert into an independent product, during the reaction, it reduces an associated cofactor in the process, which is in-tum required for and utilized during the conversion of the unsaturated lactone to the saturated lactone. This cofactor is however regenerated at the end of the conversion to re-participate in in the co-substrate’s reaction. Further, both, the reaction involving the co-substrate, as well as the conversion of the unsaturated lactone to the saturated lactone, are carried out in presence of an enzyme each, which helps in the respective reaction and conversion.

It is the presence of this coupled reaction, aided by the presence of cofactor, co substrate and enzymes that makes the conversion of the unsaturated lactone to the saturated lactone possible as well as efficient. As a result of this process, the yields of the saturated lactone is much higher, when compared to a process that does not involve such a coupled reaction. The process of the present disclosure also enables the reaction at high substrate concentration and in a relatively short incubation time.

The present disclosure thus relates to a process for bio-transforming an unsaturated lactone to produce a saturated lactone, said process comprising reduction of said unsaturated lactone in the presence of a coupled reaction, wherein the reduction is facilitated by hydrogenation of the unsaturated lactone by a reduced cofactor. In embodiments of the present disclosure, the coupled reaction is a reductase-dehydrogenase coupled reaction, as the process involves these two enzymes, reductase and dehydrogenase, during the reaction and conversion mentioned above, respectively.

The present disclosure thus relates to a process for bio-transforming an unsaturated lactone to produce a saturated lactone, said process comprising reduction of said unsaturated lactone in the presence of a coupled reaction, wherein the said reduction is carried out in presence of microorganism that facilitate the reductase-dehydrogenase coupled reaction or in presence of the reductase and dehydrogenase enzymes produced by the said microorganism.

The process of the present disclosure in particular relates to conversion of the unsaturated lactone to the saturated lactone through biotransformation, wherein the unsaturated lactone is an unsaturated d-lactone selected from a group comprising 2-decen-5-olide, 2-dodecen-5-olide and 2-tetradecen-5-olide or any combination thereof; and wherein the bio-transformation results in a corresponding saturated d-lactone selected from a group comprising 5-decanolide, 5-dodecanolide and 5-tetradecanolide, respectively.

In embodiments of the present disclosure, the unsaturated lactone is an alkyl lactone derived from the bark (or oil thereof) of Cryptocaria massoia or Massoia tree and is selected from a group comprising C-10 massoia lactone, C-12 massoia lactone and C-14 massoia lactone, or any combination thereof; and wherein the bio transformation results in a corresponding saturated d-lactone selected from a group comprising d-decalactone, d-dodecalactone and d-tetradecalactone, respectively.

Thus, in embodiments herein, the present disclosure relates to a process for bio transforming 2-decen-5-olide or C-10 massoia lactone to produce a 5-decanolide or d-decalactone, said process comprising reduction of said 2-decen-5-olide or C- 10 massoia lactone in the presence of a reductase-dehydrogenase coupled reaction, wherein the reduction is facilitated by hydrogenation of the 2-decen-5- olide or C-10 massoia lactone by a reduced cofactor.

Similarly, in embodiments herein, the present disclosure relates to a process for bio transforming 2-dodecen-5-olide or C-12 massoia lactone to produce a 5-dodecanolide or d-dodecalactone, said process comprising microbial reduction of said 2-dodecen-5- olide or C-12 massoia lactone in the presence of a reductase-dehydrogenase coupled reaction, wherein the reduction is facilitated by hydrogenation of the 2-dodecen-5- olide or C-12 massoia lactone by a reduced cofactor.

Similarly, in embodiments herein, the present disclosure relates to a process for bio-transforming 2-tetradecen-5-olide or C-14 massoia lactone to produce a 5- tetradecanolide or d-tetradecalactone, said process comprising microbial reduction of said 2-tetradecen-5-olide or C-14 massoia lactone in the presence of a reductase-dehydrogenase coupled reaction, wherein the reduction is facilitated by hydrogenation of the 2-tetradecen-5-olide or C-14 massoia lactone by a reduced cofactor. In the present disclosure, the reductase employed in the reductase-dehydrogenase coupled reaction is enoate reductase (ERED) and the dehydrogenase employed in the reductase-dehydrogenase coupled reaction is glucose dehydrogenase (GDH).

During the process of the present disclosure, the hydrogenation of the unsaturated lactone is carried out in presence of the enoate reductase (ERED). Thus, the coupled reaction provided by the embodiments of the present disclosure works as follows:

• a co-substrate undergoes dehydrogenation in presence of GDH enzyme and a cofactor to convert to its product;

• upon conversion, the cofactor gains the hydrogen so released, and is converted to its reduced form;

• the reduced cofactor then in presence of the ERED enzyme helps in conversion of the unsaturated lactone to its saturated counterpart during a hydrogenation reaction. During this reaction, the said reduced cofactor donates its hydrogen, to convert the unsaturated lactone to its saturated counterpart, and in-tum reverts to its oxidized form;

• this oxidized cofactor is now ready to re-participate in the dehydrogenation reaction of converting co-substrate into its product.

In the present disclosure, the cofactor employed is selected from a group comprising Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP). As stated above, the cofactor is reduced during oxidation of a co-substrate in presence of the said GDH; and the reduced cofactor is selected from a group comprising NADH and NADPH.

Upon the said hydrogenation reaction as mentioned above, the cofactor is converted to an oxidized form which in-tum facilitates oxidation or dehydrogenation of the co-substrate. The oxidized cofactor is therefore selected from a group comprising NAD⁺ and NADP⁺.

Thus, during the coupled reaction of the present disclosure, NAD⁺ or NADP⁺ participate in the dehydrogenation reaction of the co-substrate and are consequently reduced to NADH or NADPH, respectively, which in-tum facilitate the microbial reduction of unsaturated lactone to saturated lactone in presence of ERED. The NADH or NADPH lose their hydrogens during the conversion process to convert back to NAD⁺ or NADP⁺ respectively, to re-participate in the dehydrogenation reaction. The process of the present disclosure is therefore an irreversible enzymatic biotransformation of unsaturated lactone to the corresponding saturated lactone.

The co-substrate that participates in the coupled reaction of the present disclosure is glucose. This glucose, acting as co-substrate, undergoes dehydrogenation reaction to convert to sodium gluconate in the presence of NAD⁺ or NADP⁺. During this reaction, NaOH is converted to H2O, and in the process NAD⁺ or NAD P⁺ are reduced to NADH or NADPH, respectively.

In embodiments herein, the reductase-dehydrogenase coupled reaction of the present disclosure is represented by figure 1. The ERED-GDH coupled reaction of the present disclosure is highly efficient and converts at least 10% of the unsaturated lactone to saturated lactone. The process also increases the yield of saturated lactone by at least 50% when compared to a process for conversion of unsaturated lactone to saturated lactone without the coupled reaction.

As mentioned previously, since the process of the present disclosure is a bio transformation process, it is important that an appropriate biological organism is employed for facilitating the said coupled reaction or for producing enzymes that participate in the said reaction. In the present disclosure, this organism or the host cell is Escherichia coli.

Thus, in embodiments herein, the E.coli is engineered to carry out the coupled reaction of the present disclosure to enable bio-transformation of the unsaturated lactone to the saturated lactone. In particular, this is carried out by engineering the E. coli with the genes important for the reductase and dehydrogenase enzymes that facilitate the coupled reaction. The said genes for ERED and GDH may be obtained from any source including a fungus, a bacteria or a plant known to a person skilled in the art, but are preferably taken from Bacillus subtilis. Similarly, in embodiments herein, the E.coli is engineered to produce the ERED and GDH enzymes to carry out the coupled reaction of the present disclosure to enable bio transformation of the unsaturated lactone to the saturated lactone. In particular, this is carried out by engineering the E.coli with the genes important for the reductase and dehydrogenase enzymes and allowing production of the said enzymes by the E.coli. The said genes for ERED and GDH may be obtained from any source including a fungus, a bacteria or a plant known to a person skilled in the art, but are preferably taken from Bacillus subtilis.

Accordingly, the gene sequences from B. subtilis are preferably codon optimized before their expression in E.coli, and synthesized. This is carried out by any technique known to a person skilled in the art for such codon optimization.

In preferred embodiments, the codon optimized sequence of ERED is represented by sequence set forth as Sequence ID Nos. 1; whereas the codon optimized sequence of GDH is represented by sequence set forth as Sequence ID Nos. 2.

Once synthesized, the codon optimized genes are cloned in a suitable vector for expression. Any suitable method known to a person skilled in the art for cloning of the codon optimized sequence(s) into the expression vector is employed, and all such methods fall within the purview of the cloning performed herein. In a non-limiting embodiment, the process employed for cloning comprises cloning of the sequence(s) at restriction sites including but not limiting to Ndel and BamHl.

Further, in one embodiment of the present disclosure, only one codon optimized sequence is cloned into a vector for expression in the host organism. Accordingly, the present disclosure provides a vector comprising the codon optimized sequence of ERED represented by sequence set forth as Sequence ID Nos. 1. Alternatively, the present disclosure provides a vector comprising the codon optimized sequence of GDH represented by sequence set forth as Sequence ID Nos. 2. In an alternate embodiment of the present disclosure, both the codon optimized sequences are cloned into a vector for expression in the host organism. Accordingly, the present disclosure provides a vector comprising the codon optimized sequence of ERED represented by sequence set forth as Sequence ID Nos. 1 and the codon optimized sequence of GDH represented by sequence set forth as Sequence ID Nos. 2.

Thus, the present disclosure provides a vector comprising the codon optimized sequence as set forth in Sequence ID No. 1 or 2 or a combination thereof.

Once the vector(s) of the present disclosure are prepared, the process of transforming the host organism, preferably an E.coli is carried out. Any suitable method known to a person skilled in the art for transforming of the host organism with the vector(s) of the present disclosure is employed, and all such methods fall within the purview of the transformation performed herein. In a preferred embodiment, the process employed for transformation involves transformation of competent cells of E.coli BL21 DE3 by heat shock method.

In embodiments herein, the transformation in the present disclosure, in accordance with the above embodiments, comprises transforming the host organism with one or two vectors. In one embodiment, the host organism is transformed with a vector comprising the codon optimized sequence of ERED represented by sequence set forth as Sequence ID Nos. 1. Alternatively, the host organism is transformed with a vector comprising the codon optimized sequence of GDH represented by sequence set forth as Sequence ID Nos. 2. Further however, the present disclosure also provides a host organism that comprises both the vectors together. Thus, in one embodiment, the present disclosure provides a host organism having one vector comprising the codon optimized sequence of ERED represented by sequence set forth as Sequence ID Nos. 1 and another vector comprising the codon optimized sequence of GDH represented by sequence set forth as Sequence ID Nos. 2.

In a further alternate embodiment of the present disclosure, the host organism is transformed with a single vector comprising both, the codon optimized sequence of ERED represented by sequence set forth as Sequence ID Nos. 1 and the codon optimized sequence of GDH represented by sequence set forth as Sequence ID Nos. 2. Thus, in one embodiment, the present disclosure provides transforming the host organism with a single vector comprising the codon optimized sequence of ERED represented by sequence set forth as Sequence ID Nos. 1 and the codon optimized sequence of GDH represented by sequence set forth as Sequence ID Nos. 2.

Thus, the present disclosure provides a host cell comprising at least one vector described above. More particularly, the present disclosure provides a host cell, preferably E. coli and contains a vector comprising the codon optimized sequence as set forth in Sequence ID No. 1 and 2 or both or comprises two individual vectors each comprising the said Sequence ID Nos. 1 and 2, respectively.

In embodiments of the present disclosure, the vector employed in the process herein is selected from a group comprising pMAL vector pET vector and pCDFDuet vector, preferably a pMAL-c5X vector.

The vector employed for the expression of the codon optimized genes for expression of the GDH and ERED preferably also comprise a coding region for a protein that enables expression of the sequence as a fusion protein. One of the protein expression systems employed is maltose binding protein (MBP), but any suitable alternative known to a person skilled in the art may also be employed. Accordingly, in one embodiment, the vector constructs of the present disclosure comprise of a coding region for maltose binding protein (MBP) at the N-terminal region of the cloned gene/sequence, to obtain fusion proteins MBP-ERED and MBP-GDH from the vector constructs.

Once the vector(s) are transformed into the host organism, they are screened for positive clones, by checking the protein expression by the clones through SDS- PAGE, for expression of MBP-ERED fusion protein or MBP-GDH fusion protein, or both, depending on the initial type and configuration of the vector transformed.

The positive clones of host organism, preferably E.coli, are then grown in a respective media, incubated, and expression of the desired sequence(s) is induced. The cells are then further cultured in a culture media for obtaining soluble proteins. The host cells are then harvested by centrifugation and re-suspended in a buffer solution, before carrying out separation technique to separate and isolate the protein of interest. In an embodiment, the media for growing the host organism includes but is not limited to 2XYT media, Luria broth media or any minimal media suitably and known to a person skilled in the art for growing said host organism, such as E.coli.

In an exemplary embodiment, once the positive clones of host organism are identified, they are grown in a respective media including but not limited to 2XYT media, and incubated at a temperature of about 37°C till the OD of the culture reaches about 0.5. The protein expression was induced with a suitable inducer, including but not limited to about 0.1M IPTG (isopropyl b-D-l- thiogalactopyranoside) or about lOg/1 lactose. The cells are further cultured at temperature ranging from about 16°C to about 37°C, preferably about 25 °C, for time period ranging from about 12 hours to about 36 hours, preferably about 18 hours resulting in soluble proteins. The cells are harvested by centrifugation, preferably at a speed of about 5000 RPM for about 10 minutes at a temperature of about 4°C and resuspended in a buffer solution, including but not limited to about 0.1M phosphate buffer (pH 7.0). SDS-PAGE was carried out to observe separation of the proteins profile of the E.coli cells producing ERED, GDH or both proteins together, depending on the original vector configuration.

In embodiments of the present disclosure, the host cells harbouring the vector comprising the codon optimized sequence of ERED represented by sequence set forth as Sequence ID Nos. 1 (designated as pMALc5x:ERED); and the host cells harbouring the vector comprising the codon optimized sequence of GDH represented by sequence set forth as Sequence ID Nos. 2 (designated as pMALc5x:GDH) are inoculated separately for a seed culture of appropriate quantity with required quantity of selection marker antibiotic, such as ampicillin. Once, each of the cultures reach an OD of about 0.5, the two cultures are mixed and inoculated in appropriate quantity of 2XYT media in a fermenter, incubated and the expression of the desired sequence(s) is induced. The cells are then further cultured in a culture media for obtaining soluble proteins. The host cells are then harvested by centrifugation and re-suspended in a buffer solution, before carrying out separation technique to separate and isolate the protein of interest. As mentioned above, the incubation occurs at temperature of about 37°C and the protein expression was induced with a suitable inducer, including but not limited to about 0.1M IPTG (isopropyl b-D-l-thiogalactopyranoside) or about lOg/1 lactose. The further culturing is carried out at temperature ranging from about 16°C to about 37°C, preferably about 25 °C, for time period ranging from about 12 hours to about 36 hours, preferably about 18 hours. The centrifugation is carried out at preferably at a speed of about 5000 RPM for about 10 minutes at a temperature of about 4°C; the buffer solution, includes but is not limited to about 0.1M phosphate buffer (pH 7.0); and the separation is carried out by SDS-PAGE to observe separation of the protein profile of the E.coli cells producing ERED, GDH or both proteins together, depending on the original vector configuration.

Accordingly, the engineered host cells of the present disclosure are capable of carrying out the bio-transformation process of the present disclosure via the ERED-GDH coupled reaction described above, for converting unsaturated lactone to its saturated counterpart. The bio-transformation may accordingly be carried out either in presence of the host cells as-such capable of producing the ERED- GDH enzymes, or in presence the ERED-GDH enzymes as such.

The biotransformation of the unsaturated lactone to produce the saturated lactone is carried out via a reaction mixture that comprises at least one source of unsaturated lactone, a cofactor for facilitating the coupled reaction and hydrogenation of the unsaturated lactone, the engineered host microorganism of the present disclosure, glucose and a buffer solution. The reaction mixture can comprise host microorganism either as a whole cell or as a lysate prepared by lysing the cell by a homogenizer at about 6000 Psi for two round or by employing lysozyme based method, at a concentration of about 1 mg/ml.

Alternatively, the biotransformation of the unsaturated lactone to produce the saturated lactone is carried out via a reaction mixture that comprises at least one source of unsaturated lactone, a cofactor for facilitating the coupled reaction and hydrogenation of the unsaturated lactone, the ERED enzyme, the GDH enzyme, glucose and a buffer solution.

Thus, in embodiments of the present disclosure, the reaction mixture comprises at least one unsaturated lactone or a source thereof, a cofactor in its oxidized form, at least one microorganism (whole cell or cell lysate) engineered to express the sequences set forth in Sequence ID Nos. 1 and/or 2, glucose and a buffer solution to maintain pH of the reaction mixture. Alternatively, the reaction mixture instead of the microorganisms as such, comprises the enzymes performing the coupled reaction described in the present disclosure.

In exemplary embodiments of the present disclosure, the reaction mixture comprises an unsaturated d-lactone selected from a group comprising 2-decen-5- olide, 2-dodecen-5-olide and 2-tetradecen-5-olide or any combination thereof, NAD⁺ or NADP⁺, at least one microorganism engineered to express the sequences set forth in Sequence ID Nos. 1 and/or 2 or enzymes thereof, glucose and a buffer solution to maintain pH of the reaction mixture.

In further exemplary embodiments of the present disclosure, the reaction mixture comprises an unsaturated d-lactone selected from a group comprising C-10 massoia lactone, C-12 massoia lactone and C-14 massoia lactone, or any combination thereof, NAD⁺ or NADP⁺, at least one microorganism engineered to express the sequences set forth in Sequence ID Nos. 1 and/or 2 or enzymes thereof, glucose and a buffer solution to maintain pH of the reaction mixture.

In another exemplary embodiment of the present disclosure, the reaction mixture comprises an unsaturated d-lactone in the form of massoia bark oil, NAD⁺ or NADP⁺, at least one microorganism engineered to express the sequences set forth in Sequence ID Nos. 1 and/or 2 or enzymes thereof, glucose and a buffer solution to maintain pH of the reaction mixture.

The bio-transformation via the reaction mixture is carried out at a pH ranging from about 6 to about 8, and is maintained by a buffer system selected from a group comprising phosphate buffer, potassium phosphate buffer and TRIS HC1 buffer; at a temperature ranging from about 25°C to about 35°C. The reaction is carried at a slow rotation speed of about 500 RPM and for a time period of about 1 hour. Preferably, the pH is maintained at 7 and the temperature is set to about 30°C.

In embodiments of the present disclosure, the bio-transformation reaction of the present disclosure via the reaction mixture is scaled up to about 500 ml reaction by carrying out the reaction for a time period of about 20 hours with continuous stirring at 500 RPM. At various time intervals, an aliquot of the reaction sample was drawn out for analysing the conversion of the said unsaturated lactone.

Upon completion of the bio-transformation process, the saturated lactone, selected from 5-decanolide, d-decalactone, 5-dodecanolide, d-dodecalactone, 5- tetradecanolide or d-tetradecalactone or any combination thereof, is extracted from the reaction mixture by mixing the mixture with an organic solvent selected from a group comprising ethyl acetate, diethyl ether, pentane, dichloromethane and diisopropyl ether, preferably ethyl acetate, at a ratio of about 1 : 1 to form a layer of organic solvent. The mixing is optionally facilitated by vortexing at about 2500 RPM for about 2 minutes and the said layer is then separated by a separating funnel or centrifugation to obtain clear layer of the organic solvent comprising the saturated lactone. This layer is analysed by gas chromatography for presence of the saturated lactone. Preferably, the extraction process using the organic solvent is repeated three times and the extracts so obtained are pooled. The pooled extract is distilled in the rotavapor to remove the ethyl acetate to leave behind the concentrated saturated lactone as the final product.

Thus, in an exemplary embodiment, upon completion of the bio-transformation process, the saturated lactone, selected from 5-decanolide, d-decalactone, 5- dodecanolide, d-dodecalactone, 5-tetradecanolide or d-tetradecalactone or any combination thereof, is extracted from the reaction mixture by mixing the mixture with ethyl acetate, at a ratio of about 1 : 1 to form a layer of said ethyl acetate. The mixing is optionally facilitated by vortexing at about 2500 RPM for about 2 minutes and the said layer is then separated by a separating funnel or centrifugation to obtain a further layer of clear ethyl acetate comprising the saturated lactone. This layer is analysed by gas chromatography for presence and concentrate of the saturated lactone. The aforementioned process using the ethyl acetate is repeated three times and the extracts so obtained are pooled. The pooled extract is distilled in the rotavapor to remove the ethyl acetate and leave behind the concentrated saturated lactone as the final product.

As mentioned previously, the ERED-GDH coupled reaction of the present disclosure is highly efficient and converts at least 10% of the unsaturated lactone to saturated lactone. The process also increases the yield of saturated lactone by at least 50% when compared to a process for conversion of unsaturated lactone to saturated lactone without the coupled reaction.

Thus, in total the present disclosure relates to a process for bio-transforming an unsaturated lactone selected from a group comprising 2-decen-5-olide, 2-dodecen- 5-olide and 2-tetradecen-5-olide or any combination thereof; to produce a saturated lactone, particularly saturated d-lactone, selected from a group comprising 5-decanolide, 5-dodecanolide and 5-tetradecanolide, respectively; said process comprising reduction of said unsaturated lactone in the presence of a reductase-dehydrogenase (ERED-GDH) coupled reaction, wherein the reduction is facilitated by hydrogenation of the unsaturated lactone by a reduced cofactor.

The unsaturated lactone employed in the present disclosure may also be an alkyl lactone derived from the bark of Cryptocaria massoia or Massoia tree and is selected from a group comprising C-10 massoia lactone, C-12 massoia lactone and C-14 massoia lactone, or any combination thereof; and wherein the bio-transformation results in a corresponding saturated d-lactone selected from a group comprising d-decalactone, d-dodecalactone and d-tetradecalactone, respectively.

The cofactor employed in the process is selected from a group comprising Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP), which is reduced to NADH or NADPH, respectively, during oxidation of a co-substrate in presence of the said dehydrogenase. The co substrate employed herein is glucose.

Once the cofactor facilitates hydrogenation of the unsaturated lactone, the cofactor is converted to an oxidized form (NAD⁺ and NADP⁺) which in-tum facilitates oxidation or dehydrogenation of the co-substrate. The bio-transformation of the present disclosure is carried out by a microorganism host, preferably E.coli which is engineered to carry at least one vector comprising a codon optimized sequence of enoate reductase (ERED) and/or glucose dehydrogenase (GDH) or both, as set forth in Sequence ID Nos. 1 and 2, respectively. Once engineered, the host cell or the enzymes produced by the engineered host cell along with the unsaturated lactone or a source thereof (such as massoia bark oil), the cofactor and the co-substrate are provided in a reaction mixture along with glucose as co-substrate and buffer, for the bio transformation of the present disclosure, via the coupled reaction. The reaction mixture can comprise host microorganism either as a whole cell or as a lysate prepared by lysing the cell by a homogenizer at about 6000 Psi for two round or by employing lysozyme based method, at a concentration of about 1 mg/ml. Alternatively, the reaction mixture comprises the enzymes produced by the said host microorganism.

The converted saturated lactones are thereafter extracted and analysed to ascertain the content and the yield of conversion. The lactone so separated are used as flavouring agents in industrial applications.

As mentioned previously, saturated lactones produced according to the process of the present disclosure has a highly desirable, mild cream like scent and flavour and is hence suitable for use in flavour compositions. The present disclosure thus also provides for a flavouring agent comprising the saturated lactone produced from unsaturated lactone by the reductase -dehydrogenase coupled bio-transformation process of the present disclosure.

While the instant disclosure is susceptible to various modifications and alternative forms, specific aspects thereof has been shown by way of examples and drawings and are described in detail below. However, it should be understood that it is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and the scope of the invention as defined by the appended claims. EXAMPLES

The present disclosure is further described with reference to the following examples, winch are only illustrative in nature and should not be construed to limit the scope of the present disclosure in any manner

Before describing the experiments conducted in detail, it is noted that the C-10 and C-12 lactones employed in the example section below are obtained from massoia bark oil which contains these lactones along with other components such as terpenes like undecatriene. These different components of the massoia bark oil were separated into different receivers with highest purity in a batch distillation column. The C-10 and C-12 massoia lactones were purified therefrom to a purity of up to about 95% or greater and employed in the examples below. Alternatively, some examples also employ massoia bark oil directly as the source for C-10, C12 and/or C-14 massoia lactone.

Further, the host organism used in the present disclosure is BL21(DE3) competent E.coli obtained from New England BioLabs, USA (Catalog Number: C2527I, Lot Number: 10018136). On the other hand, the vectors/plasmids used to transform the said host organism are pMAL-c5x vector or PET 28/pET21a vector. While pMAL-c5x vector was obtained from New England BioLabs, USA (Catalog Number N8108S) with relevant sequence and information available at https://intemation3i.neb com/products/rs8108-pmal~c5x~

vectof#Pfoduct%20jnform¾tion; the PET 28/pET21a vector was obtained from Merck KGaA (Catalog Number 69864-3) with relevant sequence and information available at h¾tp://wwwjnerckmslispo e com/IN/en/product/pET-28a÷-DNA-

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Extraction and Purification

The product(s) obtained after each experiment conducted in the examples below was extracted from the biotransformation mixture with ethyl acetate. The bio transformed mixture and ethyl acetate were mixed (1 : 1), layers were separated by separating funnel. The clear layer of ethyl acetate was analyzed by Gas chromatography. The extraction process was preferably repeated three times and the extracts were pooled. The pooled extract is distilled in the rotavapor to remove the ethyl acetate while concentrated saturated product(s) is left as the final product.

Example 1

Cloning of ERED and GDH into an expression vector

The nucleotide sequences coding for the ERED (enoate reductase) gene and GDH (glucose dehydrogenase) gene in Bacillus subtilis were taken as a template and sequences optimized for their expression in Escherichia coli were synthesized. The synthesized gene sequences were subsequently cloned in pMAL-c5X vector at Ndel and BamHl sites. The vector comprises a coding region for maltose binding protein (MBP) at the N-terminal region of the cloned gene, to facilitate production of the ERED and GDH enzymes as fusion proteins in the form of MBP-ERED and MBP- GDH respectively. The vectors so prepared were designated as pMALc5x:ERED (figure 2a) and pMALc5x:GDH (figure 2b), respectively. Example 2

Transformation of E.coli with the cloned vectors comprising sequences coding for ERED and GDH

The vector constructs prepared in example 1 above were transformed into Escherichia coli BL21-DE3 competent cells by heat shock method and screened for positive clones by checking the protein expression by the clones through SDS- PAGE. Expression of MBP-ERED and MBP-GDH was optimized for obtaining higher level of soluble proteins. This was done by adding lactose in the medium for upregulating the Lac Operon. The positive clones of transformed E.coli cells expressing MBP-ERED and MBP-GDH were grown separately in individual fermenters. The E.coli cells harbouring the relevant vectors were grown in 2XYT media (MP Biomedical) and incubated at 37°C till the OD of the culture reaches to 0.5. The protein expression was then induced either with 0.1M IPTG (Isopropyl b-D-l-thiogalactopyranoside) or lOg/L Lactose. The cells were further cultured at 25 °C for nearly 18 hours resulting in soluble proteins. The cells were harvested by centrifugation and resuspended in 0.1M Phosphate buffer (pH 7.0) and subjected to separation by SDS-PAGE.

The SDS-PAGE showed separation of the proteins profile of E.coli cells producing ERED, GDH (figure 3). Example 3

Coculture of E.coli cells harbouring pMALc5x:ERED and pMALc5x:GDH

The E.coli cells harbouring plasmids pMALc5x:ERED or pMALc5x:GDH were inoculated for a seed culture of 10 ml separately with required quantity of selection marker antibiotic (Ampicillin at 100pg/ml). After, the above culture reached an OD of 0.5, the two cultures were mixed and inoculated in 2L of 2XYT media in a single fermenter. The further steps of culturing cells including incubation, induction of protein expression, further culturing and harvesting by centrifugation and separation by SDS-PAGE were followed as described for individual vector harbouring E.coli cells in Example 2. The SDS-PAGE showed the protein profiles of E.coli cells producing ERED individually, GDH individually and both proteins together. The co-culture of E. coli cells expressing both the proteins together are marked in figure 3.

Further, as an alternative to mixing of individual cultures as defined above, it is also possible to mix the enzymes produced by individual E. coli cells of Example 2, and use the same for Biotransformation in the subsequent examples that use coculture model.

Example 4

Biotransformation with whole E.coli cells harbouring pMALc5x:ERED

The conversion of unsaturated lactones (C-10 and C- 12) from massoia bark oil to saturated d-decalactone and d-dodecalactone, respectively, was performed by a hydrogenation reaction in the presence of NADH, facilitated by E.coli whole cells that harbour pMALc5x:ERED and consequently express MBP-ERED. Reaction mixture of 5ml volume was prepared, containing 250 mg (50 g/L) of massoia bark oil, 1.75 mg (0.35g/L) of NADH, potassium phosphate buffer to maintain 0.1M concentration in the mixture and the E.coli cells at OD 50 in the 5ml reaction. The reaction was carried out in a thermomixer (Eppendorf) set at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, 1.0 ml of the reaction mixture was mixed with 1.0 ml of ethyl acetate, and vortexed at about 2500 RPM for 2 minutes followed by centrifugation to separate the clear phase comprising the lactone product. The extracted product was further analysed in GC-FID.

In the above reaction, about 4% of C-10 massoia lactone was converted to d- decalactone, however, no significant conversion of C-12 massoia lactone could be measured.

Example 5

Biotransformation with cell lysates of E.coli cells harbouring pMALc5x:ERED

The E.coli cells harbouring pMALc5x:ERED and consequently expressing MBP- ERED were lysed by a homogenizer at about 6000 Psi for two round, and the crude cell lysate was used in the reaction for conversion of unsaturated lactones in massoia bark oil to saturated d-lactones. NADH was added in the reaction mixture to carry out the hydrogenation reaction. Alternatively, the cell lysates can also be obtained by lysozyme based method, at a concentration of about 1 mg/ml.

Reaction mixture was prepared similar to example 1, and briefly, 5ml of reaction mixture contained 250 mg (50 g/L) of massoia bark oil, 1.75 mg (0.35g/L) of NADH, potassium phosphate buffer to maintain 0.1M concentration in the mixture and the cell lysate of E.coli cells with OD 50. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, again, 1.0 ml of the reaction mixture was mixed with 1.0 ml of ethyl acetate, and vortexed for 2 minutes followed by centrifugation to separate the clear phase comprising the lactone product. The extracted product was further analysed in GC-FID. GC analysis showed that about 1% of C-10 massoia lactone was converted to d-decalactone however, no significant conversion of C-12 massoia lactone could be measured.

Example 6

Biotransformation with mixture of whole E.coli cells harbouring pMALc5x:ERED and whole E.coli cells harbouring pMALc5x:GDH

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of massoia bark oil, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and E.coli cells at OD 50 expressing both ERED and GDH individually (each cell harbouring either pMALc5x:ERED or pMALc5x:GDH grown separately). The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 44% of C-10 massoia lactone was converted to d- decalactone and about 12% of C-12 massoia lactone was converted to d- dodecalactone. Further, it was observed that NAD gets converted to NADH, utilized by ERED to perform hydrogenation reaction and in the process regenerating NAD again with the conversion of glucose to gluconic acid by GDH.

Example 7

Biotransformation with mixture of cell lysates of E.coli cells harbouring pMALc5x:ERED and cell lysates of E.coli cells harbouring pMALc5x:GDH

The E.coli cells individually expressing MBP-ERED and MBP-GDH (each cell harbouring either pMALc5x:ERED or pMALc5x:GDH grown separately) were lysed by a homogenizer and crude cell lysates have been used in the reaction mixture for conversion of unsaturated lactones in massoia bark oil to produce saturated d-lactones. 5ml of reaction mixture was prepared containing 250 mg (50 g/L) of massoia bark oil, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and E.coli cell lysates containing both ERED and GDH individually. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 33% of C-10 massoia lactone was converted to d- decalactone and about 11% of C-12 massoia lactone was converted to d- dodecalactone. Further, it was observed that NAD gets converted to NADH, utilized by ERED to perform hydrogenation reaction and in the process regenerating NAD again with the conversion of glucose to gluconic acid by GDH.

Example 8

Biotransformation with whole co-cultured E.coli cells harbouring both pMALc5x:ERED and pMALc5x:GDH

The E.coli cells obtained from co-culturing as described in Example 3 were used for the preparation of the reaction mixture.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of massoia bark oil, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and co-cultured E.coli cells (at OD 100 in the reaction mixture) expressing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID. GC analysis showed that about 45% of C-10 massoia lactone was converted to d-decalactone and about 12% of C-12 massoia lactone was converted to d-dodecalactone. Example 9

Biotransformation with cell lysates of co-cultured E.coli cells harbouring both pMALc5x:ERED and pMALc5x:GDH

The E.coli cells obtained from co-culturing as described in Example 3 were further lysed by a homogenizer and crude lysate of co-cultured cells was used for the source of ERED and GDH enzymes in the reaction mixture.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of massoia bark oil, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and cell lysate of co-cultured E.coli cells (at OD 100 in the reaction mixture) expressing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID. GC analysis showed that about 25% of C-10 massoia lactone was converted to d-decalactone and about 10% of C-12 massoia lactone was converted to d-dodecalactone.

Example 10

Biotransformation of C-12 massoia lactone with whole E.coli cells harbouring pMALc5x:ERED

The conversion of C-12 massoia lactone to d-dodecalactone was performed by a hydrogenation reaction with whole E.coli cells expressing with MBP-ERED in the presence of NADH. The example was performed in a manner similar to example 4, with the only difference being the source of the C-12 massoia lactone. In the reaction mixture herein, instead of employing massoia bark oil, purified C-12 massoia lactone was used.

Reaction mixture of 5ml volume was prepared, containing 250 mg (50 g/L) of C- 12 massoia lactone, 1.75 mg (0.35g/L) of NADH, potassium phosphate buffer to maintain 0.1M concentration in the mixture and the E.coli cells at OD 50 in the 5 ml reaction. The reaction was carried out in a thermomixer (Eppendorf) set at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, 1.0 ml of the reaction mixture was mixed with 1.0 ml of ethyl acetate, and vortexed at about 2500 RPM for 2 minutes followed by centrifugation to separate the clear phase comprising the lactone product. The extracted product was further analysed in GC-FID.

In the above reaction, about 2% of C-12 massoia lactone was converted to d-dodecalactone.

Example 11 Biotransformation of C-12 massoia lactone with cell lysates of E.coli cells harbouring pMALc5x:ERED

The example was performed in a manner similar to example 5, with the only difference being the source of the C-12 massoia lactone. In the reaction mixture herein, instead of employing massoia bark oil, purified C-12 massoia lactone was used.

Reaction mixture of 5ml was prepared containing 250 mg (50 g/L) of C-12 massoia lactone, 1.75 mg (0.35g/L) of NADH, potassium phosphate buffer to maintain 0.1M concentration in the mixture and the lysed E.coli cells at OD 50. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, again, 1.0 ml of the reaction mixture was mixed with 1.0 ml of ethyl acetate, and vortexed for 2 minutes followed by centrifugation to separate the clear phase comprising the lactone product. The extracted product was further analysed in GC-FID.

GC analysis showed that about 2% of C-12 massoia lactone was converted to d-dodecalactone.

Example 12 Biotransformation of C-12 massoia lactone with mixture of whole E.coli cells harbouring pMALc5x:ERED and whole E.coli cells harbouring pMALc5x:GDH

The example was performed in a manner similar to example 6, with the only difference being the source of the C-12 massoia lactone. In the reaction mixture herein, instead of employing massoia bark oil, purified C-12 massoia lactone was used.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-12 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and E.coli cells at OD 50 expressing both ERED and GDH individually (each cell harbouring either pMALc5x:ERED or pMALc5x:GDH grown separately). The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 43% of C-12 massoia lactone was converted to d-dodecalactone.

Example 13

Biotransformation of C-12 massoia lactone with mixture of cell lysates of E.coli cells harbouring pMALc5x:ERED and cell lysates of E.coli cells harbouring pMALc5x:GDH

The example was performed in a manner similar to example 7, with the only difference being the source of the C-12 massoia lactone. In the reaction mixture herein, instead of employing massoia bark oil, purified C-12 massoia lactone was used.

The E.coli cells individually expressing MBP-ERED and MBP-GDH (each cell harbouring either pMALc5x:ERED or pMALc5x:GDH grown separately) were lysed by a homogenizer and crude cell lysates have been used in the reaction mixture for conversion of unsaturated lactones in massoia bark oil to produce saturated d-lactones.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-12 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and the E.coli cell lysates (at OD 50) containing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID. GC analysis showed that about 30% of C-12 massoia lactone was converted to d-dodecalactone.

Example 14

Biotransformation of C-12 massoia lactone with whole co-cultured E.coli cells harbouring both pMALc5x:ERED and pMALc5x:GDH The E.coli cells obtained from co-culturing as described in Example 3 were used for the preparation of the reaction mixture.

The example was performed in a manner similar to example 8, with the only difference being the source of the C-12 massoia lactone. In the reaction mixture herein, instead of employing massoia bark oil, purified C-12 massoia lactone was used.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-12 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and co-cultured E.coli cells (at OD 100 in the reaction mixture) expressing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID. GC analysis showed that about 39% of C-12 massoia lactone was converted to d-dodecalactone.

Example 15

Biotransformation of C-12 massoia lactone with cell lysates of co-cultured E.coli cells harbouring both pMALc5x:ERED and pMALc5x:GDH

The example was performed in a manner similar to example 9, with the only difference being the source of the C-12 massoia lactone. In the reaction mixture herein, instead of employing massoia bark oil, purified C-12 massoia lactone was used.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-12 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and cell lysate of co-cultured E.coli cells (at OD 100 in the reaction mixture) expressing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 33% of C-12 massoia lactone was converted to d- dodecalactone.

Example 16

Biotransformation of C-10 massoia lactone with whole E.coli cells harbouring pMALc5x:ERED

The conversion of C-10 massoia lactone to d-decalactone was performed by a hydrogenation reaction with whole E.coli cells expressing with MBP-ERED in the presence of NADH. The example was performed in a manner similar to example 10, with the only difference being that instead of C-12, C-10 massoia lactone was used.

Reaction mixture of 5ml volume was prepared, containing 250 mg (50 g/L) of C- 10 massoia lactone, 1.75 mg (0.35g/L) of NADH, potassium phosphate buffer to maintain 0.1M concentration in the mixture and the E.coli cells at OD 50 in the 5ml reaction. The reaction was carried out in a thermomixer (Eppendorf) set at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID. In the above reaction, about 3% of C-10 massoia lactone was converted to d-decalactone.

Example 17

Biotransformation of C-10 massoia lactone with cell lysates of E.coli cells harbouring pMALc5x:ERED The conversion of C-10 massoia lactone to d-decalactone was performed by a hydrogenation reaction with cell lysates of E.coli cells expressing MBP-ERED, in the presence of NADH. The example was performed in a manner similar to example 11, with the only difference being that instead of C-12, C-10 massoia lactone was used. Reaction mixture of 5ml volume was prepared, containing 250 mg (50 g/L) of C- 10 massoia lactone, 1.75 mg (0.35g/L) of NADH, potassium phosphate buffer to maintain 0.1M concentration in the mixture and the lysed E.coli cells at OD 50 in the 5ml reaction. The reaction was carried out in a thermomixer (Eppendorf) set at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

In the above reaction, about 2% of C-10 massoia lactone was converted to d-decalactone. Example 18

Biotransformation of C-10 massoia lactone with mixture of whole E.coli cells harbouring pMALc5x:ERED and whole E.coli cells harbouring pMALc5x:GDH The example was performed with whole E.coli cells in a manner similar to example 12, with the only difference being that instead of C-12, C-10 massoia lactone was used.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-10 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and E.coli cells at OD 50 expressing both ERED and GDH individually (each cell harbouring either pMALc5x:ERED or pMALc5x:GDH grown separately). The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 29% of C-10 massoia lactone was converted to d- decalactone.

Example 19

Biotransformation of C-10 massoia lactone with mixture of cell lysates of E.coli cells harbouring pMALc5x:ERED and cell lysates of E.coli cells harbouring pMALc5x:GDH

The example was performed with lysed E.coli cells in a manner similar to example 13, with the only difference being that instead of C-12, C-10 massoia lactone was used. 5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-10 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and the E.coli lysates (at OD 50) containing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 20% of C-10 massoia lactone was converted to d-decalactone.

Example 20

Biotransformation of C-10 massoia lactone with whole co-cultured E.coli cells harbouring both pMALc5x:ERED and pMALc5x:GDH

The example was performed with co-cultured E.coli cells in a manner similar to example 14, with the only difference being that instead of C-12, C-10 massoia lactone was used.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-10 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and the co-cultured E.coli cells (at OD 100) expressing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 26% of C-10 massoia lactone was converted to d-decalactone.

Example 21

Biotransformation of C-10 massoia lactone with cell lysates of co-cultured E.coli cells harbouring both pMALc5x:ERED and pMALc5x:GDH

The example was performed with co-cultured E.coli cell lysates in a manner similar to example 15, with the only difference being that instead of C-12, C-10 massoia lactone was used.

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-10 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and the E.coli cell lysates (at OD 100) containing both ERED and GDH. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 13% of C- 10 massoia lactone was converted to d-decalactone.

Example 22

Biotransformation of C-10 massoia lactone to produce d-decalactone at fermenter level

A scale up experiment in 500ml reaction volume maintaining the pH at 7.0 in a fermenter with 1L gross volume was carried out. Reaction mixture was prepared containing 25g (50 g/L) of C-10 massoia lactone (95% purity), 175 mg (0.35g/L) of NAD, 70g (0.7M) of glucose, potassium phosphate buffer to maintain 0.1M concentration in the mixture and E.coli cells at OD 10 expressing both ERED and GDH individually (each cell harbouring either pMALc5x:ERED or pMALc5x:GDH grown separately). The temperature of the fermenter was set to 30°C. The pH of the reaction was maintained at 7.0 with the help of 10% NaOH and 5% Hydrochloric acid. The reaction in the fermenter was carried out for 20 hours with a continuous stirring at 500 RPM. At various time intervals, an aliquot of the reaction sample was drawn out. The reaction samples were analysed as described in the Example 4.

With increase in reaction time, an increase in the conversion of C-10 massoia lactone to d-decalactone was observed almost linearly and about 94% conversion was observed at the 20th hour of reaction (figure 4).

Similar scale-up experiment with co-cultured E. coli cells is also likely to result in a similar conversion and thus, the biotransformation of the present disclosure is capable of being performed at an industrial/large scale.

Example 23 Biotransformation with whole E.coli cells harbouring a single pCDFDuet vector comprising both codon optimized genes (ERED and GDH)

5ml of reaction mixture was prepared containing 250 mg (50 g/L) of C-10 massoia lactone, 1.75 mg (0.35g/L) of NAD, 450mg (0.5M) of glucose, and potassium phosphate buffer to maintain 0.1M concentration in the mixture and E.coli cells at OD 50 expressing both ERED and GDH together. The reaction was carried out at 30°C for 1 hour at 500 RPM. After 1 hour of reaction, extraction with ethyl acetate was carried out in a manner similar to previous examples, and the extracted product was further analysed in GC-FID.

GC analysis showed that about 40% of C-10 massoia lactone was converted to d-decalactone.

Additional embodiments and features of the present disclosure will be apparent to one of ordinary skill in art based on the description provided herein. The embodiments herein provide various features and advantageous details thereof in the description. Descriptions of well-known/conventional methods and techniques are omitted so as to not unnecessarily obscure the embodiments herein.

The foregoing description of the specific embodiments will so fully reveal the general nature of the embodiments herein that others can, by applying current knowledge, readily modify and/or adapt for various applications such specific embodiments without departing from the generic concept, and, therefore, such adaptations and modifications should and are intended to be comprehended within the meaning and range of equivalents of the disclosed embodiments. It is to be understood that the phraseology or terminology employed herein is for the purpose of description and not of limitation. Therefore, while the embodiments in this disclosure have been described in terms of preferred embodiments, those skilled in the art will recognize that the embodiments herein can be practiced with modification within the spirit and scope of the embodiments as described herein.

Any discussion of documents, acts, materials, devices, articles and the like that has been included in this specification is solely for the purpose of providing a context for the disclosure. It is not to be taken as an admission that any or all of these matters form a part of the prior art base or were common general knowledge in the field relevant to the disclosure as it existed anywhere before the priority date of this application.

While considerable emphasis has been placed herein on the particular features of this disclosure, it will be appreciated that various modifications can be made, and that many changes can be made in the preferred embodiments without departing from the principles of the disclosure. These and other modifications in the nature of the disclosure or the preferred embodiments will be apparent to those skilled in the art from the disclosure herein, whereby it is to be distinctly understood that the foregoing descriptive matter is to be interpreted merely as illustrative of the disclosure and not as a limitation.

Claims

We Claim:

1. A process for bio-transforming an unsaturated lactone to produce a saturated lactone, said process comprising reduction of said unsaturated lactone in the presence of a reductase-dehydrogenase coupled reaction, wherein the reduction is facilitated by hydrogenation of the unsaturated lactone by a reduced cofactor.

2. The process as claimed in claim 1, wherein the unsaturated lactone is selected from a group comprising 2-decen-5-olide, 2-dodecen-5-olide and 2-tetradecen-5-olide or any combination thereof; and wherein the bio transformation results in a corresponding saturated d-lactone selected from a group comprising 5-decanolide, 5-dodecanolide and 5-tetradecanolide, respectively.

3. The process as claimed in claim 1, wherein the unsaturated lactone is an alkyl lactone derived from the bark of Cryptocaria massoia or Massoia tree and is selected from a group comprising C-10 massoia lactone, C-12 massoia lactone and C-14 massoia lactone, or any combination thereof; and wherein the bio-transformation results in a corresponding saturated d- lactone selected from a group comprising d-decalactone, d-dodecalactone and d-tetradecalactone, respectively.

4. The process as claimed in claim 1, wherein the reductase is enoate reductase (ERED) and the dehydrogenase is glucose dehydrogenase (GDH).

5. The process as claimed in claim 1, wherein the hydrogenation of the unsaturated lactone is carried out in presence of enoate reductase (ERED).

6. The process as claimed in claim 1, wherein the cofactor is selected from a group comprising Nicotinamide adenine dinucleotide (NAD) and Nicotinamide adenine dinucleotide phosphate (NADP).

7. The process as claimed in claim 1, wherein the cofactor is reduced during oxidation of a co-substrate in presence of the said dehydrogenase; and wherein the reduced cofactor is selected from a group comprising NADH and NADPH.

8. The process as claimed in claim 7, wherein the co-substrate is glucose.

9. The process as claimed in claim 1, wherein upon said hydrogenation, the cofactor is converted to an oxidized form which in-tum facilitates oxidation of the co-substrate as claimed in claim 7; and wherein the oxidized cofactor is selected from a group comprising NAD⁺ and NADP⁺.

10. The process as claimed in claim 1, wherein the reductase-dehydrogenase coupled reaction is an irreversible enzymatic reaction.

11. The process as claimed in claim 1, wherein the biotransformation of an unsaturated lactone to produce the saturated lactone is carried out via a reaction mixture comprising at least one unsaturated lactone or a source thereof, the cofactor in its oxidized form, the co-substrate, at least one microorganism engineered to express the sequences set forth in Sequence ID Nos. 1 and 2, and a buffer to maintain pH of the reaction mixture; and wherein the reaction mixture can comprise the microorganism either as a whole cell or as a lysate prepared by lysing the cell by a homogenizer at about 6000 Psi for two rounds or by employing lysozyme based method, at a concentration of about 1 mg/ml.

12. The process as claimed in claim 1, wherein the biotransformation of an unsaturated lactone to produce the saturated lactone is carried out via a reaction mixture comprising at least one unsaturated lactone or a source thereof, the cofactor in its oxidized form, the co-substrate, enoate reductase (ERED), glucose dehydrogenase (GDH), and a buffer to maintain pH of the reaction mixture.

13. The process as claimed in any of claims 11 or 12, wherein the biotransformation is carried out at a pH ranging from about 6 to about 8, and is maintained by a buffer system selected from a group comprising phosphate buffer and TRIS HC1; at a temperature ranging from about 25°C to about 35°C.

14. The process as claimed in any of claim 11 or 12, wherein the saturated lactone is extracted from the reaction mixture by mixing the mixture with an organic solvent selected from a group comprising ethyl acetate, diethyl ether, pentane, dichloromethane and diisopropyl ether, at a ratio of 1 : 1 to form a layer of organic solvent, and separating the said layer by a separating funnel or chromatography to obtain clear layer of organic solvent comprising the saturated lactone.

15. The process as claimed in claim 14, wherein the extraction is repeated 2 or 3 times, and the layers formed each time are pooled, followed by distilling of the pooled layers in a rotavapor to remove the organic solvent for obtaining the saturated lactone.

16. The process as claimed in claim 1, wherein the reductase-dehydrogenase coupled reaction converts at least 10% of the unsaturated lactone to saturated lactone.

17. The process as claimed in claim 1, wherein the reductase-dehydrogenase coupled reaction increases the yield of saturated lactone by at least 50% when compared to a process for conversion of unsaturated lactone to saturated lactone without the coupled reaction.

18. A codon optimized sequence of enoate reductase (ERED) and glucose dehydrogenase (GDH) as set forth in Sequence ID Nos. 1 and 2, respectively.

19. The codon optimized sequence as claimed in claim 18, wherein the enoate reductase and glucose dehydrogenase sequences are derived from Bacillus subtilis and are codon optimized for expression in Escherichia coli.

20. A vector comprising the codon optimized sequence as set forth in Sequence ID No. 1 or 2 or a combination thereof.

21. The vector as claimed in claim 20, wherein the vector has a coding region for a protein that enables expression of the sequence as a fusion protein; and wherein the vector is selected from a group comprising pMAL vector, pET vector and pCDFDuet vector; and wherein the protein is a maltose binding protein.

22. The vector as claimed in claim 21, wherein the vector is a pMAL-c5X vector.

23. A host cell comprising at least one vector as claimed in claim 20.

24. The host cell as claimed in claim 23, wherein the host cell is Escherichia coli and comprises a vector comprising the codon optimized sequence as set forth in Sequence ID No. 1 and 2 or both or comprises two individual vectors each comprising the said Sequence ID Nos. 1 and 2, respectively.

25. A flavouring agent comprising a saturated lactone produced from unsaturated lactone by the reductase-dehydrogenase coupled bio- transformation process of claim 1.