Classifications

• • A—HUMAN NECESSITIES
  • A23—FOODS OR FOODSTUFFS; TREATMENT THEREOF, NOT COVERED BY OTHER CLASSES
  • A23L—FOODS, FOODSTUFFS OR NON-ALCOHOLIC BEVERAGES, NOT OTHERWISE PROVIDED FOR; PREPARATION OR TREATMENT THEREOF
  • A23L27/00—Spices; Flavouring agents or condiments; Artificial sweetening agents; Table salts; Dietetic salt substitutes; Preparation or treatment thereof
  • A23L27/30—Artificial sweetening agents
• • 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
  • 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
  • C12P19/18—Preparation of compounds containing saccharide radicals produced by the action of a glycosyl transferase, e.g. alpha-, beta- or gamma-cyclodextrins
• • 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
  • C12N9/10—Transferases (2.)
• • C—CHEMISTRY; METALLURGY
  • C12—BIOCHEMISTRY; BEER; SPIRITS; WINE; VINEGAR; MICROBIOLOGY; ENZYMOLOGY; MUTATION OR GENETIC ENGINEERING
  • C12Y—ENZYMES
  • C12Y204/00—Glycosyltransferases (2.4)
  • C12Y204/01—Hexosyltransferases (2.4.1)

Definitions

• the invention relates to a preparation method of rebaudioside C, in particular to a biological preparation method of rebaudioside C.
• Sweeteners are a class of food additives that are widely used in the production of foods such as beverages and confectionery. They can be added during the production of foods or appropriately diluted as a substitute for sucrose during home baking. Sweeteners include natural sweeteners and artificial sweeteners, the former including sucrose, high fructose corn syrup, honey, and the like, the latter including aspartame, saccharin, and the like.
• Stevia is a natural sweetener extracted from plant stevia and is currently widely used in foods and beverages. The extract of Stevia has a variety of steviosides including rebaudioside, and the different batch components of naturally extracted stevioside vary greatly, requiring subsequent purification.
• the traditional method of production of rebaudioside C is extracted from stevia leaves.
• 10 kg of stevia leaves are extracted to obtain about 111 g of a product having a purity of 87.6%.
• the production cost of Rebaudioside C by traditional extraction method is lower than that of Rebaudio A (about 60% dry weight). Higher, production is also limited, limiting its commercial application.
• the technical problem to be solved by the present invention is to overcome the deficiencies of the prior art and provide a method for preparing rebaudioside C by enzymatic method, which can produce high purity rebaudioside at a low cost and a short cycle. C product.
• the present invention adopts the following technical solutions:
• the glycosyl donor comprises one or two of a glucose-based donor, a rhamnosyl donor, UDP-glucose or UDP consisting of sucrose, sucrose synthase and UDP.
• a rhamnose donor is UDP-rhamnose.
• a UDP-glucose regeneration system consisting of sucrose, sucrose synthase and UDP is preferred, and UDP glucose is relatively expensive, and is regenerated by UDP-glucose. The system can significantly reduce costs.
• the UDP-glycosyltransferase i.e., uridine diphosphate glucosyltransferase, abbreviated UGT, is known
• UGT-A from Stevia rebaudiana
• One or two of -B is known.
• the UDP-glycosyltransferase is UGT-A from Stevia, the amino acid sequence of the UGT-A having at least 60% identity to the sequence 2 shown in the Sequence Listing.
• amino acid sequence of UGT-A is at least 70% identical to sequence 2 shown in the Sequence Listing.
• amino acid sequence of UGT-A has at least 80% identity to sequence 2 shown in the sequence listing.
• amino acid sequence of UGT-A has at least 90% identity to sequence 2 shown in the sequence listing.
• amino acid sequence of UGT-A is identical to sequence 2 shown in the Sequence Listing.
• the UDP-glycosyltransferase comprises UGT-A from Stevia and UGT-B from rice; the UDP-glycosyltransferase is added to the reaction system in two steps, and the first step is to add UGT- B, the second step is to join UGT-A.
• the amino acid sequence of UGT-A has at least 60% identity with sequence 2 shown in the sequence listing; and/or the amino acid sequence of UGT-B has the sequence 4 shown in the sequence listing. At least 60% consistency.
• the amino acid sequence of the UGT-A is at least 70% identical to the sequence 2 shown in the sequence listing; and/or the amino acid sequence of the UGT-B and the sequence 4 shown in the sequence listing. Has at least 70% consistency.
• amino acid sequence of the UGT-A has at least 80% identity with the sequence 2 shown in the sequence listing; and/or, the amino acid sequence of the UGT-B has the sequence 4 shown in the sequence listing. At least 80% consistency.
• amino acid sequence of the UGT-A has at least 90% identity with the sequence 2 shown in the sequence listing; and/or the amino acid sequence of the UGT-B and the sequence 4 shown in the sequence listing Has at least 90% consistency.
• the reaction can be carried out in an aqueous phase system at a temperature of 4 to 50 ° C and a pH of 5.0 to 9.0.
• the reaction is carried out in an aqueous phase system at a temperature of 35-45 ° C and a pH of 7.5-8.5.
• reaction is carried out in a phosphate buffer solution.
• the reaction system contains a recombinant cell of UDP-glycosyltransferase and a cell permeable agent.
• the cell permeability agent is toluene, and the volume ratio of toluene in the reaction system is 1-3%.
• Rebaudio C product that meets the requirements for use can be obtained by purification treatment.
• a specific purification method is post-treatment including separation of the resin, according to which the rebaudioside C having a purity of up to 95% can be obtained. product.
• the recombinant cell is a microbial cell. More preferably, the microorganism is Escherichia coli, Saccharomyces cerevisiae or Pichia pastoris.
• the first step reaction substrate is sweet leaf raspberry glycosides
• the UDP-glycosyltransferase is UGT-B from rice
• the amino acid sequence of UGT-B from rice has at least 80 % consistency
• the second step reaction substrate is a reaction solution containing the first step reaction product durgtoside A
• the UDP-glycosyltransferase is UGT-A from Stevia
• the amino acid sequence of UGT-A from Stevia has at least 80% consistency.
• the substrate is dulcectin A
• the UDP-glycosyltransferase is UGT-A from Stevia
• the amino acid sequence of UGT-A from Stevia has at least 80% consistency.
• the present invention has the following advantages compared with the prior art:
• the method for preparing rebaudioside C by enzymatic method provided by the invention has important application value. Since the growth rate of microorganisms is much faster than plants, the method of the invention can greatly reduce the production cost, shorten the production cycle, and greatly Improve the competitiveness of products; in addition, the stevia content in plants is low, and there are many different structures of stevioside, it is difficult to extract relatively pure products, and the method of extracting rebaudioside C from stevia leaves has been In contrast, the enzymatic preparation method of the present invention can provide a product with higher purity, and thus can be more economically used in the food industry such as beverages, and will further expand its application range.
• the invention mainly provides two routes for synthesizing Rebaudio C:
• the UGT-A or UGT-B used in the present invention may be present in the form of an enzyme lyophilized powder or present in recombinant cells.
• UGT-A or UGT-B can be obtained as follows:
• Recombinant Escherichia coli (or other microbial) expression strains of UGT-A or UGT-B were obtained by molecular cloning technology and genetic engineering technology, and then recombinant Escherichia coli was fermented to prepare UGT-A or UGT.
• -B recombinant cells, or lyophilized powder of UGT-A or UGT-B prepared from the above recombinant cells.
• the recombinant plasmid was transformed into Escherichia coli BL21 (DE3), and the expression of the target protein was induced by IPTG to obtain a recombinant Escherichia coli expression strain of UGT-A or UGT-B.
• the recombinant Escherichia coli expression strain containing UGT-A or UGT-B was inoculated into 4 ml of liquid LB medium at a ratio of 1%, shake culture (200 rpm) overnight at 37 ° C, and the overnight culture was inoculated at 1%. Transfer to 50 ml of liquid LB medium, shake culture (200 rpm) at 37 ° C until the OD600 value reached 0.6-0.8, and incubate at a final concentration of 0.4 mM IPTG at 20 ° C overnight.
• the cells were collected by centrifugation (8,000 rpm, 10 min), and the cells were resuspended in 5 ml of 2 mmol/L phosphate buffer (pH 7.0) to obtain the recombinant cells, and the cells were further ultrasonically disrupted in an ice bath, and the disrupted solution was centrifuged ( 8,000 rpm, 10 min), the supernatant was collected and lyophilized for 24 h to obtain the lyophilized powder.
• phosphate buffer pH 7.0
• Example 1 Preparation of recombinant E. coli cells containing UGT-A
• the UGT-A gene fragment was synthesized, and NdeI and BamHI restriction sites were added to both ends, and ligated into pUC57 vector (produced by Suzhou Jinweizhi Biotechnology Co., Ltd.).
• the UGT gene fragment was digested with restriction endonucleases NdeI and BamHI, and the purified fragment was recovered.
• the fragment was ligated into the pET30a corresponding restriction site by T4 ligase, and transformed into BL21 (DE3) strain.
• the UGT strain was inoculated into 4 ml of liquid LB medium at a ratio of 1%, shake culture (200 rpm) overnight at 37 ° C, and the overnight culture was transferred to 50 ml of liquid LB medium at a 1% inoculum and shake cultured at 37 ° C (200 rpm).
• the OD 600 value was 0.6-0.8, and the final concentration of 0.4 mM IPTG was added to shake culture at 20 ° C overnight.
• the cells were collected by centrifugation (8,000 rpm, 10 min), and the cells were resuspended in 5 ml of 2 mmol/L phosphate buffer (pH 7.0) to obtain recombinant cells containing UGT-A for catalysis.
• the recombinant cells of UGT-A prepared in Example 1 were ultrasonically disrupted in an ice bath, and the disrupted solution was centrifuged (8,000 rpm, 10 min), and the supernatant was collected and lyophilized for 24 hours to obtain a lyophilized powder of UGT-A.
• sequence 3 and sequence 4 the gene was synthesized into UGT-B gene fragment, and NdeI and BamHI restriction sites were added to both ends, and ligated into pUC57 vector (produced by Suzhou Jinweizhi Biotechnology Co., Ltd.).
• the UGT gene fragment was digested with restriction endonucleases NdeI and BamHI, and the purified fragment was recovered.
• the fragment was ligated into the pET30a corresponding restriction site by T4 ligase, and transformed into BL21 (DE3) strain.
• the UGT strain was inoculated into 4 ml of liquid LB medium at a ratio of 1%, shake culture (200 rpm) overnight at 37 ° C, and the overnight culture was transferred to 50 ml of liquid LB medium at a 1% inoculum and shake cultured at 37 ° C (200 rpm).
• the OD 600 value was 0.6-0.8, and the final concentration of 0.4 mM IPTG was added to shake culture at 20 ° C overnight.
• the cells were collected by centrifugation (8,000 rpm, 10 min), and the cells were resuspended in 5 ml of 2 mmol/L phosphate buffer (pH 7.0) to obtain recombinant cells containing UGT-B for catalysis.
• the recombinant cells of UGT-B prepared in Example 3 were ultrasonically disrupted in an ice bath, and the disrupted solution was centrifuged (8,000 rpm, 10 min), and the supernatant was collected and lyophilized for 24 hours to obtain a lyophilized powder of UGT-B.
• the UGT-A lyophilized powder prepared according to the method of Example 2 was used to catalyze the synthesis of rebaudioside C.
• sucrose sucrose synthase from Arabidopsis thaliana (hereinafter referred to as AtSUS1) is used.
• AtSUS1 sucrose synthase from Arabidopsis thaliana
• UDP-glucose regeneration system composed of UDP as a glycosyl donor.
• Example 6 Synthesis of Rebate under the catalysis of recombinant cells containing UDP-glycosyltransferase using sweet leaf raspberry as a substrate Di Di C (Route 2)
• the UGT-A lyophilized powder prepared according to the method of Example 2 and the UGT-B lyophilized powder prepared according to the method of Example 4 were used for catalytic synthesis of rebaudioside C.
• First step reaction 1L 0.05mol/L phosphate buffer (pH 8.0), 4.5g UDP rhamnose, 6.5g sweet leaf raspberry, UGT-B lyophilized powder 10g were added to the reaction system, and evenly mixed. The mixture was placed in a water bath at 40 ° C and stirred at 300 rpm for 16 h.
• the second step reaction after the first step of the reaction, the reaction solution is boiled for 10 minutes, the pH is adjusted to 8.0, 2 g UDP, 50 g of sucrose, 10 g of UGT-A lyophilized powder, and 3 g of AtSUS1 lyophilized powder are uniformly mixed and placed in 40. The reaction was stirred for 16 h at 300 rpm in a water bath.
• Example 7 Synthesis of rebaudioside C by UDP-glycosyltransferase catalyzed by dulcoside A as substrate
• UGT-A-containing recombinant cells prepared according to the method of Example 1 were used to catalyze the synthesis of rebaudioside C.
• Example 8 Synthesis of rebaudioside under the catalysis of recombinant cells containing UDP-glycosyltransferase using sweet leaf raspberry as a substrate Dixie C
• First step reaction 1L 0.05mol/L phosphate buffer (pH 8.0), 4.5g UDP rhamnose, 6.5g sweet leaf raspberry, toluene 20ml, UGT-B whole cell 40g, mixed After uniform, it was placed in a 40 ° C water bath, and the reaction was stirred at 300 rpm for 16 h.
• the second step reaction after the first step of the reaction, the reaction solution is boiled for 10 min, the pH is adjusted to 8.0, 2 g UDP, 50 g sucrose, 40 g of UGT-A whole cells, 12 g of AtSUS1 whole cells are uniformly mixed and placed in a water bath at 40 ° C. The reaction was stirred at 300 rpm for 16 h.

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