JP2013051900A - Transformant, plasmid vector, and method for producing itaconic acid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a transformant into which a plasmid vector containing a DNA that encodes a cis-aconitic acid decarboxylase (CAD) including a specific DNA is introduced, a plasmid vector that gives a host a high producing ability of itaconic acid, and a method for producing itaconic acid that can efficiently produce itaconic acid.SOLUTION: The transformant is one into which plasmid containing a DNA that encodes the CAD including any DNA of (a) to (d) is introduced, and the host is a filamentous fungus. (a) is a DNA encoding a protein including an amino acid sequence of a specific sequence; (b) is a DNA including a base sequence of a specific sequence; (c) is a DNA including a base sequence of a specific sequence different from that of (b); and (d) is a DNA hybridizable with the DNA including the base sequence of (b) or (c) under stringent conditions and encoding a protein having cis-aconitic acid decarboxylase activity.

Description

  The present invention relates to a transformant, a plasmid vector, and a method for producing itaconic acid. More specifically, the present invention relates to a transformant into which a plasmid vector containing a DNA encoding cis-aconitic acid decarboxylase consisting of a specific DNA is introduced, and a plasmid vector that imparts an itaconic acid high productivity to a host, In addition, the present invention relates to a method for producing itaconic acid capable of efficiently producing itaconic acid.

  Itaconic acid is a divalent water-soluble organic acid having an unsaturated group, and has a characteristic that a linear polymer can be formed by polymerization or copolymerization from its structure. In addition, because of its high safety, it is widely used as a raw material and additive for industrial products such as synthetic resins, synthetic fibers, adhesives and printing inks. Itaconic acid is known to be able to be produced in filamentous fungi such as Aspergillus genus such as Aspergillus terreus and Aspergillus itaconicus, and in yeast such as Candida tsukubaensis. In the industrial production of itaconic acid, A.A. terreus is used. Development of high-producing itaconic acid-producing bacteria is required for more efficient production of itaconic acid, but breeding of high-producing itaconic acid-producing bacteria involves classical random mutations such as treatment with mutagenic substances and ultraviolet irradiation. The current situation depends on the introduction method (see Patent Document 1).

  Bentley et al. In terreus, the theory that itaconic acid is biosynthesized by cis-aconitic acid decarboxylase from cis-aconitic acid produced in the citric acid cycle was proposed (see Non-Patent Document 1). Thereafter, A. Okabe et al. A cis-aconitic acid decarboxylase protein derived from terreus has been isolated and purified (see Non-Patent Document 2). Furthermore, the inventors of the present application have subsequently isolated and identified a DNA encoding cis-aconitic acid decarboxylase, and a method for producing itaconic acid using a microorganism in which a plasmid containing this DNA has been introduced into yeast cells. It has been proposed (see Patent Document 2).

JP-A-6-38774 JP 2009-27999 A

Bentley, R.A. and Thiessen C.I. P. , J .; Biol. Chem. 226: 703-720 (1957) Dwiarti L. Yamane K .; Yamatani H., et al. , Kahar P. Okabe M., et al. , J .; Biosci. Bioeng. 94: 29-33 (2002)

However, in the conventional method for producing itaconic acid using microorganisms, the production efficiency of itaconic acid is not yet sufficient, and the current situation is that further improvement in efficiency is required.
The present invention has been made in view of the above situation, and a transformant into which a plasmid vector containing a cis-aconitic acid decarboxylase encoding a specific DNA has been introduced, and a host with high itaconic acid content. It aims at providing the manufacturing method of itaconic acid which can manufacture a plasmid vector which gives productivity, and itaconic acid efficiently.

The present invention is as follows.
[1] A transformant in which a plasmid vector containing a DNA encoding cis-aconitic acid decarboxylase comprising the DNA of any one of (a) to (d) below is introduced into a host,
The transformant, wherein the host is a filamentous fungus.
(A) DNA encoding a protein comprising the amino acid sequence set forth in SEQ ID NO: 1
(B) DNA comprising the base sequence set forth in SEQ ID NO: 2
(C) DNA comprising the nucleotide sequence set forth in SEQ ID NO: 3
(D) a DNA that hybridizes with a DNA comprising the nucleotide sequence of SEQ ID NO: 2 or SEQ ID NO: 3 under stringent conditions and encodes a protein having cis-aconitic acid decarboxylase activity
[2] The transformant according to [1], wherein the host is a filamentous fungus belonging to the genus Aspergillus.
[3] The transformant according to [1] above, wherein the host is Aspergillus terreus.
[4] A plasmid vector that confers high capacity to produce itaconic acid,
DNA encoding cis-aconitic acid decarboxylase comprising the DNA according to any one of the following (a) to (d);
A plasmid vector comprising a promoter DNA consisting of the base sequence set forth in SEQ ID NO: 4.
(A) DNA encoding a protein comprising the amino acid sequence set forth in SEQ ID NO: 1
(B) DNA comprising the base sequence set forth in SEQ ID NO: 2
(C) DNA comprising the nucleotide sequence set forth in SEQ ID NO: 3
(D) a DNA that hybridizes with a DNA comprising the nucleotide sequence of SEQ ID NO: 2 or SEQ ID NO: 3 under stringent conditions and encodes a protein having cis-aconitic acid decarboxylase activity
[5] The plasmid vector according to [4] above, further comprising a terminator DNA consisting of the base sequence described in SEQ ID NO: 5.
[6] A step of culturing the transformant according to any one of the above [1] to [3];
Recovering itaconic acid produced by the transformant, and a method for producing itaconic acid.

In the transformant of the present invention, a plasmid vector containing a cis-aconitic acid decarboxylase encoding a specific DNA has been introduced into the host filamentous fungus, so that it has an excellent ability to produce high itaconic acid. I have. Therefore, it can be suitably used in a method for producing itaconic acid using a microorganism.
Since the plasmid vector of the present invention contains a plasmid vector containing DNA encoding cis-aconitic acid decarboxylase consisting of specific DNA and the specific promoter DNA described in SEQ ID NO: 4, High acid productivity can be imparted.
In addition, when the plasmid vector contains a terminator DNA consisting of the specific base sequence shown in SEQ ID NO: 5, it is possible to reliably impart a high production capacity of itaconic acid to the host.
According to the method for producing itaconic acid of the present invention, itaconic acid can be produced more efficiently than before.

The plasmid vector produced in Example 1 is shown. It is a graph which shows an itaconic acid production amount.

Hereinafter, the present invention will be described in detail.
[1] Transformant The transformant of the present invention is obtained by introducing a plasmid vector containing DNA encoding cis-aconitic acid decarboxylase (hereinafter also referred to as “CAD”) into a host. The host is a filamentous fungus.

Examples of the “filamentous fungi” that are host cells in the transformant of the present invention include itaconic acid-producing bacteria such as Aspergillus and Ustylago. Of these, Aspergillus fungi are preferred.
Examples of Aspergillus filamentous fungi include Aspergillus tereus and Aspergillus itaconicus. Among these, Aspergillus terreus is preferable, and Aspergillus terreus IFO6365 strain is particularly preferable.

The DNA encoding CAD contained in the “plasmid vector” is the DNA described in any of (a) to (d) below.
(A) DNA encoding a protein comprising the amino acid sequence set forth in SEQ ID NO: 1 (see Table 1)
(B) DNA comprising the base sequence set forth in SEQ ID NO: 2 (see Table 2)
(C) DNA comprising the base sequence set forth in SEQ ID NO: 3 (see Table 3)
(D) a protein having a cis-aconitic acid decarboxylase activity, which hybridizes with a DNA comprising the base sequence described in SEQ ID NO: 2 (see Table 2) or SEQ ID NO: 3 (see Table 3) under stringent conditions. DNA encoding

  In the present invention, the DNA described in (a) above comprises a protein having CAD activity, comprising an amino acid sequence in which one or several amino acids of SEQ ID NO: 1 have been deleted, substituted or added DNA encoding is also included.

  Specific examples of the amino acid substitution in the amino acid sequence in which one or several amino acids of the amino acid sequence shown in SEQ ID NO: 1 are substituted include, for example, the 16th Ser from the N-terminal in the amino acid sequence shown in SEQ ID NO: 1. Substitution of other amino acid (eg Ala), substitution of 236th His to other amino acid (eg Tyr), substitution of 289th Leu to other amino acid (eg Tyr), other of 290th Tyr Of 305th Asn to another amino acid (eg Lys), 308th Gly to another amino acid (eg Arg), 326th His other amino acid (For example, Tyr), substitution of Ser. 371 at another amino acid (eg, Ala), other amino acid at Ser. 394 (Eg, Pro), 396th Gln to another amino acid (eg, His), 422th Ile to another amino acid (eg, Val), 425th Ser, other amino acid (eg, Substitution to Thr), substitution of 467th Gly to another amino acid (for example, Ser), substitution of 475th Ser to another amino acid (for example, Thr), and the like.

  A DNA encoding a protein consisting of the amino acid sequence set forth in SEQ ID NO: 1 can be obtained using a conventional method for obtaining a DNA encoding the same from a known amino acid sequence as it is. For example, it can be obtained by determining the base sequence of DNA from the amino acid sequence. Further, based on the partial base sequence corresponding to the amino acid sequence, the entire base sequence can be obtained by PCR.

Since the DNA consisting of the base sequence described in SEQ ID NO: 2 is a genomic sequence encoding CAD, it contains an intron region that is not translated into an amino acid sequence.
The base sequence described in SEQ ID NO: 3 is a base sequence obtained by excluding the intron region from the base sequence described in SEQ ID NO: 2. The base sequence described in SEQ ID NO: 3 is a cDNA base sequence of a protein consisting of the amino acid sequence described in SEQ ID NO: 1, for example.

  The stringent conditions in the DNA described in (d) above include, for example, the conditions of hybridization in 4 × SSC at 65 ° C., and then washing in 0.1 × SSC for 1 hour at 65 ° C. Can do.

A DNA that hybridizes with a DNA comprising the nucleotide sequence set forth in SEQ ID NO: 2 or SEQ ID NO: 3 under stringent conditions and encodes a protein having cis-aconitic acid decarboxylase activity is, for example, the above-mentioned SEQ ID NO: 2 or PCR primers can be designed based on the nucleotide sequence set forth in SEQ ID NO: 3 and PCR can be performed using chromosomal DNA or cDNA libraries derived from various itaconic acid-producing bacteria as templates.
Applicable itaconic acid-producing bacteria are not particularly limited, and various Aspergillus fungi and yeasts can be used. Specifically, itaconic acid-producing bacteria such as various Aspergillus tereus, Aspergillus itaconicus, and Candida tsukubaensis can be mentioned.

The plasmid vector can be obtained by inserting CAD-encoding DNA into a filamentous fungus vector or the like by a known method.
Further, this plasmid vector is preferably a plasmid vector containing a specific promoter DNA described later and DNA encoding CAD.

  The transformant of the present invention can be obtained by introducing a plasmid vector into a filamentous fungus cell by a method suitable for the host (filamentous fungus). For example, introduction methods such as a protoplast-polyethylene glycol method, an electroporation method, an Agrobacterium method, and a particle gun method can be used.

[2] Plasmid vector The plasmid vector of the present invention gives a host the ability to produce itaconic acid at a high rate, and contains a DNA encoding CAD and a promoter DNA consisting of the base sequence described in SEQ ID NO: 4. It is characterized by that.
In addition, about "DNA which codes cis-aconitic acid decarboxylase (CAD)", the description in the above-mentioned transformant is applicable as it is.

  The “promoter DNA” consists of the base sequence set forth in SEQ ID NO: 4 (see Table 5 below).

  Moreover, the plasmid vector in the present invention further contains a terminator DNA consisting of the base sequence described in SEQ ID NO: 5 (see Table 7 described later) in addition to the above-mentioned DNA encoding CAD and the above promoter DNA. it can.

  Furthermore, the plasmid vector in the present invention may further contain a pyrithiamine resistance marker gene in addition to the CAD-encoding DNA and the promoter DNA.

The plasmid vector can be obtained by inserting DNA encoding CAD, promoter DNA or the like into an expression vector or the like by a known method. The expression vector used may be a shuttle vector.
Examples of the expression vector include filamentous fungal vectors. Specific examples include “pPTR I” (Takara Bio Inc.), “pPTR II” (Takara Bio Inc.), “pAUR123” (Takara Bio Inc.), and the like.

[3] Method for Producing Itaconic Acid The method for producing itaconic acid of the present invention comprises a step of culturing the above-mentioned transformant and a step of recovering itaconic acid produced by the transformant. .

In the step of culturing the transformant, host cells may be cultured by a method suitable for the host filamentous fungus.
In particular, in this culturing step, the pH of the medium can be 4 or less (particularly 3 or less, and even 2 or less). Thus, when the pH of a culture medium is low, the acid decomposition product of starch cheaper than conventionally used glucose can be used as it is as a carbon source. In addition, if starch extracted from plants is acid-decomposed with nitric acid, filamentous fungi can use nitric acid as a carbon source, so that they can be cultured without adding any other nutrient substances. Furthermore, since the medium is acidic, even if bacteria or yeast are mixed during the cultivation, the influence can be kept to a minimum.
Moreover, in this culture | cultivation process, culture | cultivation temperature can be 15-38 degreeC (especially 25-34 degreeC, Furthermore, 28-32 degreeC). When the culture temperature is in the above range, the host cells can be sufficiently cultured.

  In the step of recovering itaconic acid produced by the transformant, a method used for separating organic acids produced by culturing microorganisms from the culture can be used without particular limitation. For example, it can be separated and purified by appropriately combining means such as separation of bacterial cells by centrifugation or filtration, concentration of supernatant, various column chromatography, activated carbon treatment, filtration, recrystallization and the like. it can.

  Hereinafter, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to these examples. Here, “part” and “%” are based on mass unless otherwise specified.

<Example 1>
[1] Construction of plasmid vector (1-1) Insertion of promoter DNA into filamentous fungal vector Aspergillus nidulans-derived elongation factor gene promoter DNA was used to express the CAD1 gene using filamentous fungi as a host.
In order to obtain this promoter DNA, PCR was performed using the primers shown in Table 4 below and chromosomal DNA of Aspergillus nidulans as a template. Thereby, DNA consisting of the base sequence described in SEQ ID NO: 4 (see Table 5) was obtained.
The PCR conditions were 94 ° C. for 2 minutes, followed by 30 cycles of 94 ° C. for 30 seconds, 57 ° C. for 30 seconds, and 72 ° C. for 2 minutes.

In Table 4, the restriction enzyme KpnI was added to SEQ ID NO: 6, the recognition sequences of HindIII and SpeI were added to SEQ ID NO: 7, and the amplified promoter DNA was digested with restriction enzymes KpnI and HindIII.
Subsequently, it was combined with a filamentous fungus vector (Takara Bio Inc., “pPTR I”) digested with the restriction enzymes KpnI and HindIII. A ligation reagent (“Ligation high” manufactured by Toyobo Co., Ltd.) was used for DNA binding. The obtained plasmid DNA is designated as pPTR-P.

(1-2) Insertion of Terminator DNA In order to obtain Aspergillus nidulans-derived elongation factor gene terminator DNA, PCR was performed using the primers shown in Table 6 below and the Aspergillus nidulans chromosomal DNA as a template. Thereby, DNA consisting of the base sequence described in SEQ ID NO: 5 (see Table 7) was obtained.
The PCR conditions were 94 ° C. for 2 minutes, followed by 30 cycles of 94 ° C. for 30 seconds, 57 ° C. for 30 seconds, and 72 ° C. for 2 minutes.

  According to the instruction manual of In-fusion Advantage PCR Cloning kit (manufactured by Takara Bio Inc.) to the primers in Table 6, DNA having the same identity as the vector sequence to be bound next is added. Using the kit, the DNA of SEQ ID NO: 5 was ligated with pPTR-P digested with the restriction enzyme HindIII. The obtained plasmid DNA is designated as pPTR-PT.

(1-3) Insertion of CAD1 Gene In order to obtain Aspergillus terreus-derived CAD1 gene expression DNA, PCR was performed using the primers shown in Table 8 below and the chromosomal DNA of Aspergillus terreus IFO6365 strain as a template. Thereby, DNA consisting of the base sequence described in SEQ ID NO: 12 (see Table 9) was obtained. This CAD1 gene sequence is disclosed in JP2009-27999A, Appl. Microbiol. Biotechnol. (2008) 80, 223-229, and registered as Accession Number AB326105 in DDBJ.
PCR conditions were 30 cycles of 98 ° C. for 10 seconds, 60 ° C. for 15 seconds, and 68 ° C. for 2 minutes.

  According to the instruction manual of In-fusion Advantage PCR Cloning kit (manufactured by Takara Bio Inc.) to the primers in Table 8, DNA having the same identity as the vector sequence to be bound next is added. Using the kit, the DNA of SEQ ID NO: 12 was ligated with pPTR-PT digested with the restriction enzyme SpeI. The obtained plasmid vector (plasmid DNA) is designated as pPTR-CAD (see FIG. 1).

[2] Introduction of plasmid vector into host (Aspergillus terreus) (production of transformant)
The plasmid vector (pPTR-CAD) obtained in [1] above was introduced into filamentous fungal cells (Aspergillus terreus IFO6365 strain) by the protoplast-polyethylene glycol method. For the transformation of Aspergillus terreus, see Biosci. Biotechnol. Biochem. (2002) 66, 404-406, but when the method described therein was applied to Aspergillus terreus IFO6365 strain, it was difficult to discriminate transformants, and the growth of the bacteria was insufficient. Therefore, when the concentration of pyrithiamine hydrobromide added to the medium for separating the transformants was 0.2 μg / ml, the transformants could be clearly discriminated. The growth of the bacteria was 2.5 mg biotin, 2.5 mg nicotinic acid, 0.8 mg paraaminobenzoic acid, 1.0 mg pyridoxine hydrochloride, 2.0 mg pantothenic acid, 2.5 mg riboflavin and 20 mg choline chloride per liter of medium. Improved by adding. By adding these ideas to the conventional protoplast-polyethylene glycol method, a transformant into which pPTR-CAD was introduced (Aspergillus tereus AtCAD strain) was obtained.

[3] Evaluation of Itaconic Acid Productivity of Transformant The transformant (Aspergillus terreus AtCAD strain) obtained in [2] above was cultured with shaking in a minimal medium for filamentous fungi for 13 days. The composition of the filamentous fungal minimal medium is 10 g glucose, 3 g sodium nitrate, 1.3 g potassium chloride, 1.3 g magnesium sulfate heptahydrate, 3.8 g potassium dihydrogen phosphate, hexaammonium hexamolybdate tetrahydrate per liter. Japanese 1 mg, boric acid 10 mg, cobalt chloride hexahydrate 2 mg, copper sulfate pentahydrate 2 mg, iron sulfate heptahydrate 5 mg, manganese chloride tetrahydrate 5 mg, zinc sulfate heptahydrate 20 mg, ethylenediaminetetrahydrate Based on 50 mg of tetrasodium acetate and 0.2 mg of pyrithiamine hydrobromide, in order to improve the growth rate this time, 2.5 mg of biotin, 2.5 mg of nicotinic acid, 0.8 mg of paraaminobenzoic acid, 1 mg of pyridoxine hydrochloride, pantothene 2 mg of acid, 2.5 mg of riboflavin and 20 mg of choline chloride were added. The medium pH was 2.0 and the culture temperature was 30 ° C.
Then, a sample was prepared by collecting a part of the culture solution every 2 days from the 3rd day after the start of the culture and filtering with a filter having a pore size of 0.20 μm. Itaconic acid contained in the sample is high performance liquid chromatography (HPLC) (column: capsule pack C18 MG (5.0 × 150 mm, manufactured by Shiseido Co., Ltd.), solvent: 0.1% phosphoric acid solution, temperature: 60 ° C., flow rate: 1.5 ml / min, detection wavelength: 210 nm).
As a control (Comparative Example 1), a transformant (Aspergillus tereus AtPT strain) into which pPTR-PT into which DNA encoding CAD was not inserted was introduced was used. The results for 13 days from the culture are shown in Table 10 and FIG.

According to Table 10 and FIG. 2, in the culture solution obtained from the transformant of Example 1 (Aspergillus terreus AtCAD strain), the control (Aspergillus terreus) in which DNA encoding CAD was not inserted. Compared with Teleus AtPT strain), it was confirmed that the itaconic acid concentration increased about 26 times in 13 days of culture.
From the above, it was found that itaconic acid can be produced more efficiently by highly expressing DNA encoding cis-aconitic acid decarboxylase (CAD) in filamentous fungi (Aspergillus terreus).

Claims (6)

A transformant in which a plasmid vector containing a DNA encoding cis-aconitic acid decarboxylase comprising the DNA of any one of (a) to (d) below is introduced into a host,
The transformant, wherein the host is a filamentous fungus.
(A) DNA encoding a protein comprising the amino acid sequence set forth in SEQ ID NO: 1
(B) DNA comprising the base sequence set forth in SEQ ID NO: 2
(C) DNA comprising the nucleotide sequence set forth in SEQ ID NO: 3
(D) a DNA that hybridizes with a DNA comprising the nucleotide sequence of SEQ ID NO: 2 or SEQ ID NO: 3 under stringent conditions and encodes a protein having cis-aconitic acid decarboxylase activity   The transformant according to claim 1, wherein the host is a filamentous fungus of the genus Aspergillus.   The transformant according to claim 1, wherein the host is Aspergillus terreus. A plasmid vector that confers a high production capacity of itaconic acid on a host,
DNA encoding cis-aconitic acid decarboxylase comprising the DNA according to any one of the following (a) to (d);
A plasmid vector comprising a promoter DNA consisting of the base sequence set forth in SEQ ID NO: 4.
(A) DNA encoding a protein comprising the amino acid sequence set forth in SEQ ID NO: 1
(B) DNA comprising the base sequence set forth in SEQ ID NO: 2
(C) DNA comprising the nucleotide sequence set forth in SEQ ID NO: 3
(D) a DNA that hybridizes with a DNA comprising the nucleotide sequence of SEQ ID NO: 2 or SEQ ID NO: 3 under stringent conditions and encodes a protein having cis-aconitic acid decarboxylase activity   Furthermore, the plasmid vector of Claim 4 containing terminator DNA which consists of a base sequence of sequence number 5. Culturing the transformant according to any one of claims 1 to 3,
Recovering itaconic acid produced by the transformant, and a method for producing itaconic acid.

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