WO2019100676A1 - 一种酶改质甜菊糖的制备方法和制备用酶及应用 - Google Patents

一种酶改质甜菊糖的制备方法和制备用酶及应用 Download PDF

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WO2019100676A1
WO2019100676A1 PCT/CN2018/088358 CN2018088358W WO2019100676A1 WO 2019100676 A1 WO2019100676 A1 WO 2019100676A1 CN 2018088358 W CN2018088358 W CN 2018088358W WO 2019100676 A1 WO2019100676 A1 WO 2019100676A1
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fructosidase
stevioside
enzyme
glc
modified
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PCT/CN2018/088358
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English (en)
French (fr)
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傅荣昭
刘立辉
江名
刘玉凤
刘文山
陈小春
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邦泰生物工程(深圳)有限公司
江西邦泰绿色生物合成生态产业园发展有限公司
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Priority to PCT/CN2018/088358 priority Critical patent/WO2019100676A1/zh
Priority to US16/605,993 priority patent/US11312948B2/en
Priority to CN201880001975.2A priority patent/CN109415747B/zh
Publication of WO2019100676A1 publication Critical patent/WO2019100676A1/zh

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    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12N—MICROORGANISMS OR ENZYMES; COMPOSITIONS THEREOF; PROPAGATING, PRESERVING, OR MAINTAINING MICROORGANISMS; MUTATION OR GENETIC ENGINEERING; CULTURE MEDIA
    • C12N9/00—Enzymes; Proenzymes; Compositions thereof; Processes for preparing, activating, inhibiting, separating or purifying enzymes
    • C12N9/14—Hydrolases (3)
    • C12N9/24—Hydrolases (3) acting on glycosyl compounds (3.2)
    • C12N9/2402—Hydrolases (3) acting on glycosyl compounds (3.2) hydrolysing O- and S- glycosyl compounds (3.2.1)
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P19/00—Preparation of compounds containing saccharide radicals
    • C12P19/14—Preparation of compounds containing saccharide radicals produced by the action of a carbohydrase (EC 3.2.x), e.g. by alpha-amylase, e.g. by cellulase, hemicellulase
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12P—FERMENTATION OR ENZYME-USING PROCESSES TO SYNTHESISE A DESIRED CHEMICAL COMPOUND OR COMPOSITION OR TO SEPARATE OPTICAL ISOMERS FROM A RACEMIC MIXTURE
    • C12P19/00—Preparation of compounds containing saccharide radicals
    • C12P19/44—Preparation of O-glycosides, e.g. glucosides
    • C12P19/56—Preparation of O-glycosides, e.g. glucosides having an oxygen atom of the saccharide radical directly bound to a condensed ring system having three or more carbocyclic rings, e.g. daunomycin, adriamycin
    • C—CHEMISTRY; METALLURGY
    • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
    • C12Y—ENZYMES
    • C12Y302/00—Hydrolases acting on glycosyl compounds, i.e. glycosylases (3.2)
    • C12Y302/01—Glycosidases, i.e. enzymes hydrolysing O- and S-glycosyl compounds (3.2.1)
    • C12Y302/0108—Fructan beta-fructosidase (3.2.1.80)
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
    • A23V2250/00—Food ingredients
    • A23V2250/24—Non-sugar sweeteners
    • A23V2250/258—Rebaudioside
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
    • A23V2250/00—Food ingredients
    • A23V2250/24—Non-sugar sweeteners
    • A23V2250/262—Stevioside
    • A—HUMAN NECESSITIES
    • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
    • A23V—INDEXING SCHEME RELATING TO FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES AND LACTIC OR PROPIONIC ACID BACTERIA USED IN FOODSTUFFS OR FOOD PREPARATION
    • A23V2300/00—Processes
    • A23V2300/36—Modification in general

Definitions

  • the invention relates to the field of biomedical technology, in particular to a preparation method and an enzyme for preparation and application of the enzyme modified stevioside.
  • Stevia also known as stevioside, has a sweetness of 200-350 times that of sucrose, has no toxic side effects, is safe to eat, and studies have shown that stevioside can be used to prevent high blood pressure, diabetes, obesity, heart disease and dental caries.
  • Stevia is the third natural sugar substitute that has development value and health promotion besides sugar cane and beet sugar. It is internationally known as “the world's third sugar”.
  • Stevioside is a mixture of diterpenoid glycosides containing a variety of ingredients extracted from the leaves of the stevia herb, Stevia.
  • Stevioside (St), Rebaudioside A (RA) and Rebaudioside C (RC) have higher contents, accounting for more than 90%.
  • Natural stevioside is not sweet and has a bitter taste due to its own structure, aglycone, which has an unpleasant aftertaste, which seriously affects the taste of stevia and limits its wider industrial application. Therefore, it is important to improve the sweetness characteristics of stevioside.
  • the present invention provides a preparation method of enzyme-modified stevioside and a preparation of the backup enzyme and application thereof; the preparation method of the invention has the advantages of simple process, short time consumption, high yield and green safety.
  • the present invention provides a method for preparing an enzyme-modified stevioside, comprising:
  • ⁇ -fructosidase FFase
  • FFase ⁇ -fructosidase
  • the enzyme-modified stevioside is collected, and the stevioside raw material includes one or more of stevioside and lycopene A, and the ⁇ -fructosidase is derived from Microbacterium saccharophilum. Or Japanese Aspergillus japonicus.
  • the stevioside (St), or stevioside has a molecular formula of C 38 H 60 O 18 and has a chemical structure as shown in Formula I.
  • the Leybide A (RA), or Stevia A glycoside has the molecular formula C 44 H 70 O 23 and the chemical structure is as shown in Formula II:
  • the process adopts a biological enzymatic method, and the chemical structure of the stevioside raw material is as shown in Formula III, and the chemical structure of the enzyme-modified stevioside is as shown in Formula IV, wherein the R group includes a disaccharide Base and trisaccharide group.
  • the disaccharide group may be ⁇ -glc- ⁇ -glc-; the trisaccharide group may be ( ⁇ -glc) 2 - ⁇ -glc-; the glc is glucose (Glucose).
  • sucrose is decomposed by ⁇ -fructosidase (FFase) to obtain glucose (Glucose) and fructose (F), wherein the fructose (F) molecule is catalyzed by ⁇ -fructosidase.
  • FFase ⁇ -fructosidase
  • the ⁇ -2,6 glycosidic linkage is attached to the 6-OH of the 19-O- ⁇ -glucosyl group.
  • the fructose (F) molecule is catalyzed by ⁇ -fructosidase to bind to the 6-OH of the 19-O- ⁇ -glucosyl group of stevioside by ⁇ -2,6 glycosidic linkage to obtain a stevioside derivative (St -F) as shown in formula V.
  • the reaction also includes the beta-fructosidase catalyzing the hydrolysis of sucrose and obtaining glucose.
  • the fructose (F) molecule is linked to the 6-OH of the 19-O- ⁇ -glucosyl group of Leybide A by ⁇ -fructosidase catalyzed by ⁇ -fructosidase.
  • the ⁇ A derivative (RA-F) is as shown in Formula VI.
  • the reaction also includes the beta-fructosidase catalyzing the hydrolysis of sucrose and obtaining glucose.
  • the enzyme-modified stevioside comprises one or more of an enzyme-modified stevioside and an enzyme-modified lycopene A.
  • the enzyme-modified stevioside comprises one or more of the stevioside derivative (St-F) and the Leybide A derivative (RA-F).
  • the preparation method of the present invention can quickly and efficiently modify the stevioside raw material by the ⁇ -fructosidase to improve the post-bitter taste of stevioside.
  • the fructose group is introduced on the 19-O- ⁇ -glucosyl 6-OH of the stevioside raw material (such as St or RA) by the preparation method of the enzyme-modified stevioside to obtain an enzyme-modified stevioside (such as St-F).
  • the RA-F has a much improved sweetness profile.
  • the ⁇ -fructosidase comprises a first ⁇ -fructosidase or a second ⁇ -fructosidase
  • the genetic coding sequence of the first ⁇ -fructosidase comprises as shown in SEQ ID NO: 1.
  • the nucleotide sequence of the second ⁇ -fructosidase gene coding sequence includes the nucleotide sequence shown in SEQ ID NO: 2.
  • the ⁇ -fructosidase is produced by microbial expression, including one or more of Escherichia coli, Pichia pastoris, and Bacillus subtilis. Further, optionally, the ⁇ -fructosidase is produced by expression in E. coli.
  • the ⁇ -fructosidase is heterologously expressed in the system in which the E. coli expression is expressed.
  • the present invention preferably has an E. coli expression system which is simple and feasible, has a short culture period, low fermentation cost, and high enzyme yield.
  • the ⁇ -fructosidase of the present invention may be added to the reaction system in the form of a lyophilized powder or a crude enzyme solution.
  • the pH of the reaction solution is adjusted to be 5.0-8.0. Further optionally, the pH of the reaction solution is from 7.0 to 8.0. Preferably, the pH of the reaction solution is from 7.2 to 8.0.
  • the pH of the reaction solution of the present invention may be alkaline, which helps to increase the ⁇ -fructosidase reactivity, increase the yield of the enzyme-modified stevioside, and shorten the reaction time.
  • the reaction temperature of the reaction liquid is maintained at 20 to 45 °C. Further, optionally, the reaction temperature of the reaction liquid is maintained at 20 to 30 °C. Preferably, the reaction temperature of the reaction liquid is maintained at 20-28 °C. For example, the reaction temperature of the reaction liquid is maintained at 20 ° C, or 25 ° C, or 28 ° C, or 35 ° C.
  • the reaction time of the stirring reaction is 2-5 hours. Further optionally, the reaction time of the stirring reaction is 2-4 hours.
  • the preparation method of the invention is time-consuming, and the reaction time is a preferred reaction time. When the reaction time is increased, the conversion rate of the obtained product of the preparation method is lowered.
  • the stirring reaction is stirred at a rate of 200-300 rpm.
  • the process of collecting the enzyme-modified stevioside comprises: heating the reaction solution to denature the ⁇ -fructosidase, filtering and collecting the filtrate, and purifying the filtrate to obtain an enzyme modification.
  • the heating temperature is 85-100 ° C and the time is 0.3-1 hour.
  • the heating may be carried out at a temperature of from 90 to 100 ° C for a period of from 0.5 to 1 hour.
  • the stevioside raw material has a mass fraction of 1%-20% in the reaction solution. Further, optionally, the mass fraction of the stevioside raw material in the reaction liquid is 10%-20%. For example, the stevioside raw material has a mass fraction of 10%, or 12%, or 15%, or 20% in the reaction liquid.
  • the mass ratio of the stevioside raw material to the ⁇ -fructosidase is 1: (0.1-2). Further, optionally, the mass ratio of the stevioside raw material to the ⁇ -fructosidase is 1: (0.5-2).
  • the mass ratio of the stevioside raw material to the sucrose is 1: (1-10). Further, optionally, the mass ratio of the stevioside raw material to the sucrose is 1: (2-5).
  • the reaction solution further includes a buffer solution
  • the buffer solution includes any one or more of a phosphate buffer solution and a Tris-HCl buffer solution.
  • the buffer also includes other types of buffers.
  • the buffer includes a sodium phosphate buffer.
  • the concentration of the buffer is 10-1000 mmol/L.
  • the concentration of the buffer is from 10 to 1000 mmol/L.
  • the concentration of the buffer is from 100 to 500 mmol/L.
  • the concentration of the buffer is 100 mmol/L, or 200 mmol/L, or 500 mmol/L.
  • the enzymatic properties of ⁇ -fructosidase from different microbial species are different, including the specific activity of the enzyme, the substrate range of the enzyme, the optimum pH, the optimum temperature, the action time and the stability of the enzyme.
  • the ⁇ -fructosidase of the present invention comprises a first ⁇ -fructosidase or a second ⁇ -fructosidase; wherein the first ⁇ -fructosidase is derived from the genus Acidophilus, and the second ⁇ -fructosidase From the Japanese Aspergillus.
  • the ⁇ -fructosidase of the present invention has both hydrolase properties, can hydrolyze the fructose molecules in sucrose, and has a reverse catalyzing function, and is capable of adding fructose molecules to the stevioside and the lyoside A 19 -O- ⁇ -glucosyl on 6-OH.
  • the preparation method of the enzyme-modified stevioside provided by the first aspect of the invention has the advantages of simple process, low cost, short time consumption, and environmental protection; the enzyme-modified stevia prepared by the preparation method has extremely high Yield.
  • the prior art only supports an enzyme-catalyzed reaction in which the substrate concentration is in the range of a few thousandths, and the general conversion rate is only 40-50%, and only in the case of When the substrate concentration is close to the lowest value, the conversion rate can reach about 60%, or by adding raw materials for increasing the conversion rate; while the preparation method of the present invention can support a higher substrate concentration (such as 5%-20%).
  • the conversion rate can be close to about 90%; therefore, the preparation according to the invention is low in cost and suitable for industrial production.
  • the present invention provides an enzyme for preparing an enzyme-modified stevioside, wherein the preparation enzyme comprises ⁇ -fructosidase, and the ⁇ -fructosidase comprises a first ⁇ -fructosidase Or a second ⁇ -fructosidase, the gene coding sequence of the first ⁇ -fructosidase comprising a nucleotide sequence as shown in SEQ ID NO: 1, the second ⁇ -fructosidase gene coding sequence
  • the nucleotide sequence set forth in SEQ ID NO: 2 is included; the first ⁇ -fructosidase is derived from the genus Acidophilus, and the second ⁇ -fructosidase is derived from the genus Aspergillus in Japan.
  • the amino acid sequence of the first ⁇ -fructosidase comprises the amino acid sequence as shown in SEQ ID NO: 3.
  • the amino acid sequence of the second ⁇ -fructosidase includes the amino acid sequence set forth in SEQ ID NO: 4.
  • the gene coding sequence of the amino acid sequence shown in SEQ ID NO: 3 is represented by SEQ ID NO: 1; alternatively, the gene coding sequence of the amino acid sequence of the first ⁇ -fructosidase should be considered
  • the degenerate base, ie, the coding gene of the amino acid sequence set forth in SEQ ID NO: 3 includes the nucleotide sequence set forth in SEQ ID NO: 1, and the protective range should also protect the base simplification with SEQ ID NO: 1.
  • a nucleotide sequence of the nature, the amino acid sequence corresponding to these nucleotide sequences is still SEQ ID NO: 3.
  • the gene encoding the amino acid sequence shown in SEQ ID NO: 4 should also consider degenerate bases.
  • the ⁇ -fructosidase is expressed in a microorganism by constructing a recombinant plasmid, and the vector plasmid of the recombinant plasmid is a pET28a(+) vector plasmid. Inserting the gene coding sequence of the first ⁇ -fructosidase and/or the second ⁇ -glucosidase into the pET28a(+) vector plasmid to obtain a recombinant plasmid, which can be highly efficient and productive Heterologous expression in a microbial cell results in the first beta-fructosidase and/or the second beta-fructosidase.
  • a nucleotide sequence of a His-tag is added to the gene coding sequence of the first ⁇ -fructosidase and/or the second ⁇ -glucosidase to enable expression.
  • the protein is tagged with His, and the His tag facilitates the isolation and purification of the expressed protein, as well as analysis and tracking in experiments, such as analysis for immunoblot experiments.
  • the enzyme-modified ⁇ -glucosidase prepared by the enzyme-modified stevioside provided by the second aspect of the invention has good biological activity and high purity, and can be widely used in the fields of food sweetener preparation, biopharmaceutical and the like.
  • the preferred ⁇ -fructosidases of the present invention have higher yields, are shorter in time, and have greater biological activity and specificity than conventional fermentation systems.
  • a third aspect of the present invention provides the use of a ⁇ -fructosidase and a microorganism strain containing the ⁇ -fructosidase gene in biocatalysis, wherein the ⁇ -fructosidase is derived from Microbacterium oryzae a ⁇ -fructosidase gene encoding a Japanese Aspergillus genus, the ⁇ -fructosidase catalyzing the conversion of a compound of Formula III to a compound of Formula IV,
  • the R group is ⁇ -glc- ⁇ -glc-, ( ⁇ -glc) 2 - ⁇ -glc-, ( ⁇ -glc, ⁇ -rha-)- ⁇ -glc-, ⁇ -rha- ⁇ -glc-, ⁇ -glc-, ( ⁇ -glc, ⁇ -xyl)- ⁇ -glc- or H.
  • the glc is glucose (Glucose)
  • the rha is rhamnose
  • the xyl is xylose.
  • the process of converting the compound of the formula III into the compound of the formula IV by the ⁇ -fructosidase of the present invention further comprises: catalytically hydrolyzing the sucrose to obtain glucose.
  • the compound represented by the formula III is Stevioside; when the R group is ( ⁇ -glc) 2 - ⁇ -glc-
  • the compound represented by the formula III is Rebaudioside A; when the R group is ( ⁇ -glc, ⁇ -rha-)- ⁇ -glc-, the formula III is The compound is Rebaudioside C; when the R group is ⁇ -rha- ⁇ -glc-, the compound represented by the formula III is Dulcoside A;
  • the compound represented by the formula III is a ruthenium (Rubusoside); when the R group is ( ⁇ -glc, ⁇ -xyl)- ⁇ -glc-, the formula III
  • the compound shown is Rebaudioside F.
  • the ⁇ -fructosidase may have a fructosyl group attached to the 6-OH of the 19-O- ⁇ -glucosyl group of the compound of the formula III by a ⁇ -2,6 glycosidic bond.
  • the compound shown in IV may have a fructosyl group attached to the 6-OH of the 19-O- ⁇ -glucosyl group of the compound of the formula III by a ⁇ -2,6 glycosidic bond.
  • the ⁇ -fructosidase may bind a fructosyl group to a 6-OH of a 19-O- ⁇ -glucosyl group of the stevioside by a ⁇ -2,6 glycosidic bond; or a fructose derivative;
  • the base is attached to the 6-OH of the 19-O- ⁇ -glucosyl group of the stevioside by a ⁇ -2,6-glycosidic bond to obtain a Lepodide A derivative or the like.
  • the ⁇ -fructosidase has an amino acid sequence as shown in SEQ ID NO: 3 or SEQ ID NO: 4.
  • the ⁇ -fructosidase gene coding sequence includes the nucleotide sequence as shown in SEQ ID NO: 1 or SEQ ID NO: 2.
  • the present invention also provides a recombinant plasmid comprising a first ⁇ -fructosidase or a second ⁇ -fructosidase gene coding sequence, wherein the first ⁇ -fructosidase gene coding sequence
  • the nucleotide sequence set forth in SEQ ID NO: 1 is included, and the gene coding sequence of the second ⁇ -fructosidase includes the nucleotide sequence shown in SEQ ID NO: 2.
  • the gene coding sequence of the first ⁇ -fructosidase or the second ⁇ -fructosidase is inserted between the BamH I and Hind III restriction sites of the pET28a(+) vector plasmid.
  • the first ⁇ -fructosidase or the second ⁇ -fructosidase gene coding sequence When the first ⁇ -fructosidase or the second ⁇ -fructosidase gene coding sequence is inserted into the pET28a(+) vector plasmid, the first ⁇ -fructosidase or the second ⁇ -fruit
  • the 5' end of the glycosidase gene coding sequence can be ligated with a start codon (such as ATG) and a BamHI restriction site in the pET28a (+) vector plasmid, and a stop codon (such as TAA) and pET28a can be added to the 3' end ( +)
  • the Hind III restriction sites are ligated in the vector plasmid.
  • the invention also provides a preparation method of a recombinant plasmid, comprising:
  • the enzyme cleavage site of the double enzyme digestion reaction may be BamH I and Hind III endonuclease.
  • the preparation method of the invention adopts the biological enzymatic method, has the advantages of simple operation, short time consumption, high conversion rate and green safety, and can be widely applied to industrial scale production;
  • the final concentration of the substrate can reach 1%-20%, which is much higher than the final concentration of the traditional process substrate;
  • the enzyme-modified stevioside prepared by the preparation method of the invention has stable properties, high sweetness, greatly improved bitterness and astringency, low calorific value, and can be widely applied in the food industry and the pharmaceutical field;
  • the enzyme- ⁇ -glucosidase prepared by the invention has good biological activity and specificity.
  • FIG. 1 is a plasmid map of a recombinant plasmid pET28a-FFase01 according to an embodiment of the present invention
  • FIG. 2 is a plasmid map of a recombinant plasmid pET28a-FFase02 according to an embodiment of the present invention
  • FFase a gene coding sequence for the ⁇ -fructosidase obtained by providing an upstream primer and a downstream primer and experimentally obtained.
  • the ⁇ -fructosidase comprises a first ⁇ -fructosidase (FFase01) or a second ⁇ -fructosidase (FFase02).
  • the gene coding sequence of the first ⁇ -fructosidase includes a nucleotide sequence as shown in SEQ ID NO: 1, the first ⁇ -fructosidase is derived from the genus Acidophilus; the second ⁇ The gene coding sequence of the fructosidase comprises the nucleotide sequence as shown in SEQ ID NO: 2, and the second ⁇ -fructosidase is derived from the genus Aspergillus in Japan.
  • the base sequence of the upstream primer corresponding to the first ⁇ -fructosidase is shown in SEQ ID NO: 5, and the base sequence of the downstream primer is shown in SEQ ID NO: 6.
  • the base sequence of the upstream primer corresponding to the second ⁇ -fructosidase is shown in SEQ ID NO: 7, and the base sequence of the downstream primer is shown in SEQ ID NO: 8.
  • the restriction sites are ligated, and a stop codon (such as TAA) is added to the 3' end to be ligated to the Hind III restriction site in the pET28a(+) vector plasmid. Then, it was transferred into E. coli competent cell DH5 ⁇ , and positive clone PCR identification and sequencing were performed.
  • the recombinant plasmid pET28a-FFase01 or pET28a-FFase02 was successfully constructed by PCR product gel electrophoresis detection and sequencing to identify the size and sequence of the target fragment.
  • Figure 1 and Figure 2 show the recombinant plasmid maps of pET28a-FFase01 or pET28a-FFase02, respectively.
  • One or more of the constructed recombinant plasmids pET28a-FFase01 and pET28a-FFase02 were transferred into E. coli BL21 (DE3), and inoculated into 4 mL of LB medium at a 1% inoculum to maintain a constant 37. °C, shaking rate of 200 rpm, after overnight culture, transfer the bacterial solution to a 2 L flask containing 1 L of LB medium (50 ⁇ g/mL kanamycin) at 1% inoculation, and continue to incubate at 37 ° C until constant temperature.
  • the obtained crude enzyme solution containing FFase01 or FFase02 was identified by SDS-polyacrylamide gel electrophoresis (SDS-PAGE).
  • the molecular sizes of the FFase01 and FFase02 are similar to the theoretical calculation values of the corresponding proteins, wherein the theoretical molecular weight of FFase01 is 64 kDa, and the theoretical molecular weight of FFase02 is 70 kDa.
  • the collected crude enzyme solution can be further purified to obtain a lyophilized powder of FFase01 or FFase02.
  • ⁇ -fructosidase FFase03-FFase05 were obtained; wherein ⁇ -fructosidase FFase03 was derived from Schwanniomyces occidentalis, ⁇ -fruit Glycosidase FFase04 is derived from Lactobacillus crispatus, and ⁇ -fructosidase FFase05 is derived from Cichorium intybus.
  • a method for preparing an enzyme-modified stevioside comprising:
  • FIG. 3 is a mass spectrum of the enzyme-modified stevioside RA-F detected during the experiment, and is calculated according to the data of the reaction liquid measured by liquid chromatography. The conversion rate was 91.5%.
  • a method for preparing an enzyme-modified stevioside comprising:
  • FIG. 4 is a mass spectrum of the enzyme-modified stevioside St-F detected during the experiment, and is calculated according to the data of the reaction liquid measured by liquid chromatography. The conversion rate was 92.0%.
  • a method for preparing an enzyme-modified stevioside comprising:
  • a method for preparing an enzyme-modified stevioside comprising:
  • a method for preparing an enzyme-modified stevioside comprising:
  • a method for preparing an enzyme-modified stevioside comprising:
  • a method for preparing an enzyme-modified stevioside comprising:
  • a method for preparing an enzyme-modified stevioside comprising:

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Abstract

本发明提供了一种酶改质甜菊糖的制备方法，包括：在溶解有甜菊糖原料和蔗糖的溶液中加入β-果糖苷酶得到反应液，调节所述反应液的pH为5.0-8.0，反应温度维持在20-45℃，搅拌反应后，收集得到酶改质甜菊糖，所述甜菊糖原料包括甜菊苷和莱包迪甙A中的一种或多种，所述β-果糖苷酶来源于嗜酸微杆菌属或日本曲霉菌属。该制备方法高效简便，成本低，耗时短，转化率高，绿色环保，可以广泛适用于工业化规模生产。本发明还提供了一种酶改质甜菊糖的制备用酶及应用。

Description

一种酶改质甜菊糖的制备方法和制备用酶及应用 技术领域
本发明涉及生物医药技术领域，特别涉及一种酶改质甜菊糖的制备方法和制备用酶及应用。
背景技术
甜菊糖，又名甜菊糖苷，甜度为蔗糖的200-350倍，具有无毒副作用，食用安全，并且研究表明甜菊糖可用于预防高血压、糖尿病、肥胖症、心脏病和龋齿等病症，是一种可替代蔗糖非常理想的甜味剂。甜菊糖是继甘蔗、甜菜糖之外第三种有开发价值和健康推崇的天然蔗糖替代品，被国际上誉为“世界第三蔗糖”。
甜菊糖是从菊科草本植物甜叶菊的叶子中提取出来的一类含多种成分的双萜糖苷的混合物。其中甜菊苷(Stevioside，St)、莱包迪甙A(Rebaudioside A，RA)和莱包迪甙C(Rebaudioside C，RC)的含量较高，共占90％以上。天然甜菊糖由于其本身的结构苷元甜菊醇无甜味且具有苦涩味，会带来不愉快的后味，严重影响了甜菊糖的味质，限制了其更为广泛的工业应用。因此，改善甜菊糖的甜味特征具有重要意义。
目前，有报道利用酶法或发酵法在甜菊糖组分中引入一些新的糖分子，得到的衍生物(或称酶改质甜菊糖)的甜味特性有较大的改善，并减弱后苦涩味。然而这些生产方法大多能耗高，耗时长，纯度与产率均偏低。因此，有必要发展一种工艺简单、耗时短、成本低、产率高且绿色环保的酶改质甜菊糖的制备方法。
发明内容
为了解决上述技术问题，本发明提供了一种酶改质甜菊糖的制备方法和制 备用酶及应用；本发明所述制备方法工艺简单、耗时短、产量高和绿色安全。
第一方面，本发明提供了一种酶改质甜菊糖的制备方法，包括：
在溶解有甜菊糖原料和蔗糖(Sucrose)的溶液中加入β-果糖苷酶(FFase)得到反应液，调节所述反应液的pH为5.0-8.0，反应温度维持在20-45℃，搅拌反应后，收集得到酶改质甜菊糖，所述甜菊糖原料包括甜菊苷和莱包迪甙A中的一种或多种，所述β-果糖苷酶来源于嗜酸微杆菌属(Microbacterium saccharophilum)或日本曲霉菌属(Aspergillus japonicus)。
本发明中，所述甜菊苷(St)，或称甜菊甙，分子式为C 38H 60O 18，化学结构如式Ⅰ所示。所述莱包迪甙A(RA)，或称甜菊A苷，分子式为C 44H 70O 23，化学结构如式Ⅱ所示：
Figure PCTCN2018088358-appb-000001
所述酶改质甜菊糖的制备方法的具体工艺路线如式(1)所示：
Figure PCTCN2018088358-appb-000002
其中，所述工艺采用生物酶法，所述甜菊糖原料的化学结构通式如式Ⅲ所示，所述酶改质甜菊糖的化学结构通式如式Ⅳ所示，其中R基包括二糖基和三 糖基。所述二糖基可为β-glc-β-glc-；所述三糖基课可以为(β-glc) 2-β-glc-；所述glc为葡萄糖(Glucose)。所述蔗糖(Sucrose)经β-果糖苷酶(FFase)催化作用下分解得到葡萄糖(Glucose)和果糖(Fructose，F)，其中果糖(Fructose，F)分子在β-果糖苷酶催化作用下以β-2,6糖苷键连接至19-O-β-葡萄糖基的6-OH上。
本发明中，所述甜菊糖原料为甜菊苷(St)时，所述酶改质甜菊糖的制备方法的具体工艺路线如式(2)所示：
Figure PCTCN2018088358-appb-000003
其中，果糖(F)分子在β-果糖苷酶催化作用下以β-2,6糖苷键连接至甜菊苷的19-O-β-葡萄糖基的6-OH上，得到甜菊苷衍生物(St-F)如式Ⅴ所示。所述反应过程中还包括所述β-果糖苷酶催化蔗糖水解并得到葡萄糖。
本发明中，所述甜菊糖原料为莱包迪甙A(RA)时，所述酶改质甜菊糖的制备方法的具体工艺路线如式(3)所示：
其中，果糖(F)分子在β-果糖苷酶催化作用下以β-2,6糖苷键连接至莱包 迪甙A的19-O-β-葡萄糖基的6-OH上，得到莱包迪甙A衍生物(RA-F)如式Ⅵ所示。所述反应过程中还包括所述β-果糖苷酶催化蔗糖水解并得到葡萄糖。可选地，所述酶改质甜菊糖包括酶改质的甜菊苷和酶改质莱包迪甙A中的一种或多种。具体地，所述酶改质甜菊糖包括所述甜菊苷衍生物(St-F)和所述莱包迪甙A衍生物(RA-F)中的一种或多种。
由于甜菊苷的19位连接的糖基与苦味密切相关，而甜菊苷13-糖基与甜味相关。本发明所述的制备方法通过所述β-果糖苷酶可以快捷、有效地改性甜菊糖原料，以改善甜菊糖的后苦味。通过所述酶改质甜菊糖的制备方法在甜菊糖原料(如St或RA)的19-O-β-葡萄糖基的6-OH上引入果糖基，得到酶改质甜菊糖(如St-F或RA-F)的甜味特性有较大改善。
可选地，所述β-果糖苷酶包括第一β-果糖苷酶或第二β-果糖苷酶，所述第一β-果糖苷酶的基因编码序列包括如SEQ ID NO：1所示的核苷酸序列，所述第二β-果糖苷酶的基因编码序列包括如SEQ ID NO：2所示的核苷酸序列。
可选地，所述β-果糖苷酶通过微生物表达生成，所述微生物包括大肠杆菌、毕赤酵母和枯草芽孢杆菌中的一种或多种。进一步地，可选地，所述β-果糖苷酶通过大肠杆菌表达生成。所述β-果糖苷酶在所述大肠杆菌表达生成的体系中均属于异源表达。本发明优选地大肠杆菌表达系统，简单可行，培养周期短，发酵成本低，酶产量高。本发明所述β-果糖苷酶可以以冻干粉形式或粗酶液形式添加至反应体系中。
可选地，本发明所述制备方法中，调节所述反应液的pH为5.0-8.0。进一步可选地，所述反应液的pH为7.0-8.0。优选地，所述反应液的pH为7.2-8.0。本发明所述反应液的pH可偏碱性，有助于提升所述β-果糖苷酶反应活性，提高所述酶改质甜菊糖的产率，缩短反应时间。
可选地，所述反应液的反应温度维持在20-45℃。进一步地，可选地，所述反应液的反应温度维持在20-30℃。优选地，所述反应液的反应温度维持在20-28℃。例如，所述反应液的反应温度维持在20℃，或为25℃，或为28℃，或为35℃。
可选地，所述搅拌反应的反应时间为2-5小时。进一步可选地，所述搅拌反应的反应时间为2-4小时。本发明所述制备方法耗时短，所述反应时间为优选反应时间，当增加反应时间时，所述制备方法的得到的产品的转化率会降低。
可选地，所述搅拌反应的搅拌速率为200-300rpm。
可选地，所述收集得到酶改质甜菊糖的过程包括：对所述反应液加热以使所述β-果糖苷酶变性，过滤并收集滤液，将所述滤液纯化处理后得到酶改质甜菊糖，其中，所述加热的温度为85-100℃，时间为0.3-1小时。可选地，所述加热的温度还可以为90-100℃，时间为0.5-1小时。
可选地，所述甜菊糖原料在所述反应液中的质量分数为1％-20％。进一步地，可选地，所述甜菊糖原料在所述反应液中的质量分数为10％-20％。例如，所述甜菊糖原料在所述反应液中的质量分数为10％，或为12％，或为15％，或为20％。
可选地，所述甜菊糖原料与所述β-果糖苷酶的质量比为1：(0.1-2)。进一步地，可选地，所述甜菊糖原料与所述β-果糖苷酶的质量比为1：(0.5-2)。
可选地，所述甜菊糖原料与所述蔗糖的质量比为1:(1-10)。进一步地，可选地，所述甜菊糖原料与所述蔗糖的质量比为1:(2-5)。
可选地，，所述反应液中还包括缓冲液，所述缓冲液包括磷酸盐缓冲液和Tris-HCl缓冲液中的任意一种或多种。可选地，所述缓冲液还包括其他种类缓冲液。具体地，所述缓冲液包括磷酸钠缓冲液。可选地，所述缓冲液的浓度为10-1000mmol/L。进一步可选地，所述缓冲液的浓度为10-1000mmol/L。优选地， 所述缓冲液的浓度为100-500mmol/L。例如，所述缓冲液的浓度为100mmol/L，或为200mmol/L，或为500mmol/L。
由于不同微生物种属来源的β-果糖苷酶的酶学性质存在差异，包括酶的比活性、酶作用的底物范围、最适pH、最适温度、作用时间和酶的稳定性等方面。本发明所述β-果糖苷酶包括第一β-果糖苷酶或第二β-果糖苷酶；其中，第一β-果糖苷酶来源于嗜酸微杆菌属，第二β-果糖苷酶来源于日本曲霉菌属。本发明所述β-果糖苷酶既具有水解酶性质，可以将蔗糖中的果糖分子水解下来，有具有逆向催化功能，能够将果糖分子加合上所述甜菊苷和莱包迪甙A的19-O-β-葡萄糖基的6-OH上。
本发明第一方面所提供的酶改质甜菊糖的制备方法，所述制备方法工艺简单，成本低廉，耗时短，绿色环保；由所述制备方法制得的酶改质甜菊糖具有极高的产率。在底物(甜菊糖原料)和酶的投料比相同的情况下，现有技术仅支持底物浓度在千分之几的酶催化反应进行，一般转化率仅为40-50％，且仅在底物浓度接近最低值时，转化率才能达到60％左右，或者通过补加原料用于提高转化率；而本发明所述的制备方法可支持较高的底物浓度(如5％-20％)下，转化率可接近90％左右；因此，本发明所述的制备成本低，适于工业化生产。
第二方面，本发明还提供了一种酶改质甜菊糖的制备用酶，其中，所述制备用酶包括β-果糖苷酶，所述β-果糖苷酶包括第一β-果糖苷酶或第二β-果糖苷酶，所述第一β-果糖苷酶的基因编码序列包括如SEQ ID NO：1所示的核苷酸序列，所述第二β-果糖苷酶的基因编码序列包括如SEQ ID NO：2所示的核苷酸序列；所述第一β-果糖苷酶来源于嗜酸微杆菌属，所述第二β-果糖苷酶来源于日本曲霉菌属。
可选地，所述第一β-果糖苷酶的氨基酸序列包括如SEQ ID NO：3所示的氨 基酸序列。所述第二β-果糖苷酶的氨基酸序列包括如SEQ ID NO：4所示的氨基酸序列。
其中，所述如SEQ ID NO：3所示的氨基酸序列的基因编码序列如SEQ ID NO：1所示；可选的，所述第一β-果糖苷酶的氨基酸序列的基因编码序列应该考虑简并碱基，即如SEQ ID NO:3所示的氨基酸序列的编码基因包括如SEQ ID NO:1所示的核苷酸序列，保护范围还应该保护与SEQ ID NO:1具有碱基简并性质的核苷酸序列，这些核苷酸序列对应的氨基酸序列仍然为SEQ ID NO:3。同样的，对于所述第二β-果糖苷酶，所述如SEQ ID NO：4所示的氨基酸序列的编码基因同样应该考虑简并碱基。
可选地，所述β-果糖苷酶通过构建重组质粒在微生物中表达，所述重组质粒的载体质粒为pET28a(+)载体质粒。将所述第一β-果糖苷酶和/或第二所述β-果糖苷酶的基因编码序列插入至所述pET28a(+)载体质粒中得到重组质粒，所述重组质粒可以高效、高产的在微生物细胞中的异源表达得到所述第一β-果糖苷酶和/或所述第二β-果糖苷酶。
可选地，所述第一β-果糖苷酶和/或第二所述β-果糖苷酶的基因编码序列上增设His标签(组氨酸标签)的核苷酸序列，能使表达后的蛋白带上His标签，His标签有利于表达后蛋白的分离纯化，及在实验中的分析和追踪，比如用于免疫印迹实验时的分析。
本发明第二方面提供的酶改质甜菊糖的制备用酶—β-果糖苷酶，具有很好的生物活性，纯度高，可广泛应用于食品甜味剂制备、生物制药等领域。相比于传统其他发酵体系，本发明优选的β-果糖苷酶具有更高的产率，耗时短，具有更强的生物活性及特异性。
本发明第三方面提供了β-果糖苷酶以及含有所述β-果糖苷酶基因的微生物 菌株在生物催化中的应用，其中，所述β-果糖苷酶由来源于嗜酸微杆菌属或日本曲霉菌属的β-果糖苷酶基因编码，所述β-果糖苷酶催化式Ⅲ所示的化合物转化成式Ⅳ所示的化合物，
Figure PCTCN2018088358-appb-000005
R基是β-glc-β-glc-、(β-glc) 2-β-glc-、(β-glc，α-rha-)-β-glc-、α-rha-β-glc-、β-glc-、(β-glc，β-xyl)-β-glc-或H。其中，所述glc为葡萄糖(Glucose)，所述rha为鼠李糖(Rhamnose)，所述xyl为木糖(Xylose)。本发明所述β-果糖苷酶催化所述式Ⅲ所示的化合物转化成所述式Ⅳ所示的化合物的过程中还包括：催化水解蔗糖转化得到葡萄糖。
其中，当所述R基为β-glc-β-glc-时，所述式Ⅲ所示的化合物为甜菊苷(Stevioside)；当所述R基为(β-glc) 2-β-glc-时，所述式Ⅲ所示的化合物为莱包迪甙A(Rebaudioside A)；当所述R基为(β-glc，α-rha-)-β-glc-时，所述式Ⅲ所示的化合物为莱包迪甙C(Rebaudioside C)；当所述R基为α-rha-β-glc-时，所述式Ⅲ所示的化合物为杜克甙A(Dulcoside A)；所述R基为β-glc-时，所述式Ⅲ所示的化合物为甜茶苷(Rubusoside)；当所述R基为(β-glc，β-xyl)-β-glc-时，所述式Ⅲ所示的化合物为莱包迪甙F(Rebaudioside F)。具体地，所述β-果糖苷酶可以将果糖基以β-2,6糖苷键连接至所述式Ⅲ所示的化合物的19-O-β-葡萄糖基的6-OH上得到所述式Ⅳ所示的化合物。例如，所述β-果糖苷酶可以将果糖基以β-2,6糖苷键连接至所述甜菊苷的19-O-β-葡萄糖基的6-OH上得到甜菊苷衍生物；或将果糖基以β-2,6糖苷键连接至所述甜菊苷的19-O-β-葡萄糖基的6-OH上得到莱包迪 甙A衍生物等。
可选地，所述β-果糖苷酶具有如SEQ ID NO：3或SEQ ID NO：4所示的氨基酸序列。所述β-果糖苷酶基因编码序列包括如SEQ ID NO：1或SEQ ID NO：2所示的核苷酸序列。本发明还提供了一种重组质粒，所述重组质粒包括第一β-果糖苷酶或第二β-果糖苷酶的基因编码序列，其中，所述第一β-果糖苷酶的基因编码序列包括如SEQ ID NO：1所示的核苷酸序列，所述第二β-果糖苷酶的基因编码序列包括如SEQ ID NO：2所示的核苷酸序列。
可选地，所述第一β-果糖苷酶或所述第二β-果糖苷酶的基因编码序列插入到pET28a(+)载体质粒的BamH I和Hind III酶切位点之间。所述第一β-果糖苷酶或所述第二β-果糖苷酶的基因编码序列插入到pET28a(+)载体质粒时，所述第一β-果糖苷酶或所述第二β-果糖苷酶的基因编码序列的5’端可加入起始密码子(如ATG)与pET28a(+)载体质粒中BamHⅠ酶切位点相连，3’端可加入终止密码子(如TAA)与pET28a(+)载体质粒中Hind III酶切位点相连。
本发明还提供了一种重组质粒的制备方法，包括：
(1)提供上游引物和下游引物，所述上游引物和下游引物的碱基序列分别如SEQ ID NO:5-SEQ ID NO:8所示；
(2)提供或制备第一β-果糖苷酶或第二β-果糖苷酶基因模板，并以步骤(1)所述上游引物和所述下游引物为PCR引物，扩增所述第一β-果糖苷酶或所述第二β-果糖苷酶基因片段；
(3)取pET28a(+)载体质粒，将步骤(2)扩增得到的所述第一β-果糖苷酶或所述第二β-果糖苷酶基因片段和所述pET28a(+)载体质粒利用相同的内切酶分别进行双酶切反应，纯化回收后进行连接，得到所述重组质粒。
可选地，所述步骤(3)中，所示双酶切反应的酶切位点可以为BamH I和 Hind III内切酶。
本发明的有益效果包括以下几个方面：
1、本发明所述的制备方法采用生物酶法，操作简便，耗时短、转化率高和绿色安全，可以广泛适用于工业化规模生产；
2、本发明所述的制备方法，底物终浓度可高到达1％-20％，远远高于传统工艺底物终浓度；
3、由本发明所述的制备方法制备的酶改质甜菊糖，性质稳定，甜度高，后苦涩味极大改善，热值低，可广泛应用在食品工业及制药领域；
4、本发明所述制备用酶—β-果糖苷酶的生物活力好，特异性强。
附图说明
图1为本发明一实施例提供的pET28a-FFase01重组质粒的质粒图谱；
图2为本发明一实施例提供的pET28a-FFase02重组质粒的质粒图谱；
图3为本发明一实施例提供的RA-F的质谱图；
图4为本发明一实施例提供的St-F的质谱图。
具体实施方式
以下所述是本发明实施例的优选实施方式，应当指出，对于本技术领域的普通技术人员来说，在不脱离本发明实施例原理的前提下，还可以做出若干改进和润饰，这些改进和润饰也视为本发明实施例的保护范围。
若无特别说明，本发明实施例所采用的原料及其它化学试剂皆为市售商品。
(1)构建pET28a-FFase01、pET28a-FFase02重组质粒
a)提供上游引物和下游引物，并通过实验得到的β-果糖苷酶的基因编码序列。其中，所述β-果糖苷酶(FFase)包括第一β-果糖苷酶(FFase01)或第二β-果糖苷酶(FFase02)。所述第一β-果糖苷酶的基因编码序列包括如SEQ ID NO： 1所示的核苷酸序列，所述第一β-果糖苷酶来源于嗜酸微杆菌属；所述第二β-果糖苷酶的基因编码序列包括如SEQ ID NO：2所示的核苷酸序列，所述第二β-果糖苷酶来源于日本曲霉菌属。所述第一β-果糖苷酶对应的上游引物的碱基序列如SEQ ID NO:5所示，下游引物的碱基序列如SEQ ID NO:6所示。所述第二β-果糖苷酶对应的上游引物的碱基序列如SEQ ID NO:7所示，下游引物的碱基序列如SEQ ID NO:8所示。
b)将所述FFase01或FFase02的基因编码序列插入到pET28a(+)载体质粒的BamH I和Hind III酶切位点之间。所述FFase01或FFase02的基因编码序列插入到pET28a(+)载体质粒时，所述FFase01或FFase02的基因编码序列的5’端添加起始密码子(如ATG)与pET28a(+)载体质粒中BamHⅠ酶切位点相连，3’端还添加有终止密码子(如TAA)与pET28a(+)载体质粒中Hind III酶切位点相连。然后转入大肠杆菌感受态细胞DH5α，进行阳性克隆PCR鉴定和测序鉴定。经过PCR产物凝胶电泳检测和测序鉴定符合目的片段大小和序列，成功构建pET28a-FFase01或pET28a-FFase02重组质粒。如图1和图2分别是所示为pET28a-FFase01或pET28a-FFase02重组质粒图谱。
(2)表达β-果糖苷酶FFase01或FFase02
将构建的重组质粒pET28a-FFase01和pET28a-FFase02中的一种或多种转入大肠杆菌BL21(DE3)中，并以1％的接种量接种至含有4mL的LB培养基中，维持恒定的37℃，200rpm的摇晃速率，过夜培养后，将菌液以1％的接种量转接到含有1L的LB培养基(50μg/mL卡那霉素)的2L三角瓶中，继续37℃恒温培养至培养基中的OD600值达到0.6左右，加入终浓度为度0.1mM-1mM的诱导剂IPTG，在20-37℃条件培养12-16小时后离心收集菌体。将菌体用50mM磷酸缓冲液(pH＝7.4)进行重悬并经超声破碎和离心，收集上清液得到含有 FFase01或FFase02的粗酶液。
将表达获得的含有FFase01或FFase02的粗酶液进行SDS-聚丙烯酰胺凝胶电泳(SDS-PAGE)鉴定。本实施方式表达获得的粗酶液中，所述FFase01和FFase02的分子大小均与相应蛋白的理论计算值相近，其中，FFase01的理论分子量为64kDa，FFase02的理论分子量为70kDa。此外，对收集得到的粗酶液可进行进一步纯化，可制得FFase01或FFase02的冻干粉。
(3)FFase01或FFase02催化活性比较
按上述步骤(1)及步骤(2)的操作过程，获取其他来源的β-果糖苷酶FFase03-FFase05；其中，β-果糖苷酶FFase03来源于许旺氏酵母(Schwanniomyces occidentalis)，β-果糖苷酶FFase04来源于卷曲乳杆菌(Lactobacillus crispatus)，β-果糖苷酶FFase05来源于菊苣(Cichorium intybus)。设计反应体系：在1mL的磷酸钠缓冲液中，分别加入甜菊苷或莱包迪甙A 5mg，加入蔗糖20mg，搅拌至完全溶解；继续加入上述FFase01-FFase05中的任意一种β-果糖苷酶的粗酶液200μL(50mg)，调节pH至7.4；在20℃、200rpm搅拌速率下反应5h，收集得到酶改质甜菊糖，并评估每种β-果糖苷酶的酶活情况，见下表所示：
Figure PCTCN2018088358-appb-000006
实施例1
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入莱包迪甙A 50g和蔗糖100g，搅拌至完全溶解；继续加入10g FFase01冻干酶粉，调节pH至7.4；在35℃、250rpm搅拌 速率下反应2h，反应完成后将反应液加热至100℃热处理0.5h，使FFase01蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖RA-F 51.73g，纯度＞95％。本实施例中，每隔一定时间取反应液进行质谱分析；图3是实验过程中检测的酶改质甜菊糖RA-F的质谱图，并根据液相色谱对反应液进行测定的数据计算得到转化率为91.5％。
实施例2
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入甜菊苷50g和蔗糖100g，搅拌至完全溶解；继续加入10g FFase01冻干酶粉，调节pH至7.4；在35℃、250rpm搅拌速率下反应2h，反应完成后将反应液加热至100℃热处理0.5h，使FFase01蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖St-F51.85g，纯度＞95％。本实施例中，每隔一定时间取反应液进行质谱分析；图4是实验过程中检测的酶改质甜菊糖St-F的质谱图，并根据液相色谱对反应液进行测定的数据计算得到转化率为92.0％。
实施例3
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入甜菊苷50g和蔗糖100g，搅拌至完全溶解；继续加入10g FFase02冻干酶粉，调节pH至7.4；在28℃、250rpm搅拌速率下反应2h，反应完成后将反应液加热至100℃热处理0.5h，使FFase02蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖St-F 52.64g，纯度＞95％；实验测得转化率为92.4％。
实施例4
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入甜菊苷50g和蔗糖200g，搅拌至完全溶解；继续加入5g FFase02冻干酶粉，调节pH至7.4；在28℃、250rpm搅拌速率下反应2h，反应完成后将反应液加热至100℃热处理0.5h，使FFase02蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖St-F53.27g，纯度＞95％；实验测得转化率为93.5％。
实施例5
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入甜菊苷50g和蔗糖100g，搅拌至完全溶解；继续加入5g FFase02冻干酶粉，调节pH至8.0；在28℃、250rpm搅拌速率下反应2h，反应完成后将反应液加热至100℃热处理0.5h，使FFase02蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖St-F51.98g，纯度＞95％；实验测得转化率为91.3％。
实施例6
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入甜菊苷50g和蔗糖100g，搅拌至完全溶解；继续加入5g FFase02冻干酶粉，调节pH至7.4；在28℃、250rpm搅拌速率下反应4h，反应完成后将反应液加热至100℃热处理0.5h，使FFase02蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶 改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖St-F52.72g，纯度＞95％；实验测得转化率为92.6％。
实施例7
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入甜菊苷50g和蔗糖100g，搅拌至完全溶解；继续加入5g FFase02冻干酶粉，调节pH至8.0；在20℃、250rpm搅拌速率下反应4h，反应完成后将反应液加热至100℃热处理0.5h，使FFase02蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖St-F52.39g，纯度＞95％；实验测得转化率为92.1％。
实施例8
一种酶改质甜菊糖的制备方法，包括：
在500mL的磷酸钠缓冲液中，分别加入甜菊苷100g和蔗糖200g，搅拌至完全溶解；继续加入20g FFase02冻干酶粉，调节pH至7.4；在28℃、250rpm搅拌速率下反应2h，反应完成后将反应液加热至100℃热处理0.5h，使FFase02蛋白变性并过滤除去蛋白，收集滤液后进行喷雾干燥得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶等后处理纯化后得到酶改质甜菊糖St-F107.21g，纯度＞95％；实验测得转化率为91.3％。
以上所述实施例仅表达了本发明的几种实施方式，其描述较为具体和详细，但并不能因此而理解为对本发明专利范围的限制。应当指出的是，对于本领域的普通技术人员来说，在不脱离本发明构思的前提下，还可以做出若干变形和改进，这些都属于本发明的保护范围。因此，本发明专利的保护范围应以所附权利要求为准。

Claims (10)

  1. 一种酶改质甜菊糖的制备方法，其中，包括：
    在溶解有甜菊糖原料和蔗糖的溶液中加入β-果糖苷酶得到反应液，调节所述反应液的pH为5.0-8.0，反应温度维持在20-45℃，搅拌反应后，收集得到酶改质甜菊糖，所述甜菊糖原料包括甜菊苷和莱包迪甙A中的一种或多种，所述β-果糖苷酶来源于嗜酸微杆菌属或日本曲霉菌属。
  2. 如权利要求1所述的制备方法，其中，所述β-果糖苷酶包括第一β-果糖苷酶或第二β-果糖苷酶，所述第一β-果糖苷酶的基因编码序列包括如SEQ ID NO：1所示的核苷酸序列，所述第二β-果糖苷酶的基因编码序列包括如SEQ ID NO：2所示的核苷酸序列。
  3. 如权利要求1所述的制备方法，其中，所述搅拌反应的反应时间为2-5小时。
  4. 如权利要求1所述的制备方法，其中，所述收集得到酶改质甜菊糖的过程包括：对所述反应液加热以使所述β-果糖苷酶变性，过滤并收集滤液，将所述滤液纯化处理后得到酶改质甜菊糖，其中，所述加热的温度为85-100℃，时间为0.3-1小时。
  5. 如权利要求4所述的制备方法，其中，所述将所述滤液纯化处理的步骤包括：喷雾干燥所述滤液得到酶改质甜菊糖粗品，将所述酶改质甜菊糖粗品经硅胶树脂分离、结晶处理后得到所述酶改质甜菊糖。
  6. 如权利要求1所述的制备方法，其中，所述甜菊糖原料在所述反应液中的质量分数为1％-20％。
  7. 如权利要求1所述的制备方法，其中，所述甜菊糖原料与所述β-果糖苷 酶的质量比为1：(0.1-2)。
  8. 如权利要求1所述的制备方法，其中，所述反应液中还包括缓冲液，所述缓冲液包括磷酸盐缓冲液和Tris-HCl缓冲液中的任意一种或多种。
  9. 一种酶改质甜菊糖的制备用酶，其中，所述制备用酶包括β-果糖苷酶，所述β-果糖苷酶包括第一β-果糖苷酶或第二β-果糖苷酶，所述第一β-果糖苷酶的基因编码序列包括如SEQ ID NO：1所示的核苷酸序列，所述第二β-果糖苷酶的基因编码序列包括如SEQ ID NO：2所示的核苷酸序列；所述第一β-果糖苷酶来源于嗜酸微杆菌属，所述第二β-果糖苷酶来源于日本曲霉菌属。
  10. β-果糖苷酶以及含有所述β-果糖苷酶基因的微生物菌株在生物催化中的应用，其中，所述β-果糖苷酶由来源于嗜酸微杆菌属或日本曲霉菌属的β-果糖苷酶基因编码，所述β-果糖苷酶催化式Ⅲ所示的化合物转化成式Ⅳ所示的化合物，
    Figure PCTCN2018088358-appb-100001
    其中，R基是β-glc-β-glc-、(β-glc) 2-β-glc-、(β-glc，α-rha-)-β-glc-、α-rha-β-glc-、β-glc-、(β-glc，β-xyl)-β-glc-或H。
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