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Method for preparing L-cysteine through enzymatic conversion

A technology of cystine enzyme method and cysteine, which is applied in the direction of fermentation, etc., to achieve the effects of low efficiency, high catalytic rate and conversion rate, good economic and social benefits

Active Publication Date: 2012-06-27
NANJING UNIV +1
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0022] The above reports on the enzymatic synthesis of L-cysteine ​​by tryptophan synthase all use pure L-serine as the substrate. At present, the production costs of L-serine and L-cysteine ​​are roughly the same, so L-serine Pure enzymatic synthesis of L-cysteine ​​has no practical significance

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Embodiment 1

[0038] 1. Add 18 g of tryptophan synthase wet thallus obtained by centrifugation of 1000 mL of fermented liquid into 500 mL of transformation liquid, which contains 38 g / L L-serine in the hair acid hydrolyzate (total amino acid content 15%), 13 g of NaHS , 0.2g / L pyridoxal phosphate and 0.005g / L OP, pH 8.5, 37°C enzymatic reaction for 21h, after the reaction, the concentration of L-cysteine ​​in the conversion liquid was 36g / L, and the molar conversion of L-serine The rate is 82.2%.

[0039] 2. Centrifuge the transformation solution at 4000r / min for 15min to remove bacterial cells, adjust the supernatant to pH 1.0 with 6mol / L hydrochloric acid, and heat to remove H 2 S, activated carbon decolorization, suction filtration, the filtrate was adjusted to pH 5.0 with 5mol / L NaOH, the L-cysteine ​​in the filtrate was oxidized by air, precipitated, vacuum suction filtration, washed with pure water, and dried to obtain 16.8g L-cysteine Crude cystine, decolorized by acid solution, neutr...

Embodiment 2

[0041] 1. Add 19 g of tryptophan synthase wet thallus obtained by centrifugation of 1000 mL of fermented liquid into 500 mL of transformation liquid, which contains 46 g / L of L-serine in the hair acid hydrolyzate (total amino acid content 10%), 15 g of NaHS , 0.2g / L pyridoxal phosphate and 5g / L Tween-80, pH 9.0, 35°C enzymatic reaction for 28h, after the reaction, the concentration of L-cysteine ​​in the conversion solution is 45g / L, and the concentration of L-serine The molar conversion was 84.9%.

[0042] 2. Centrifuge the transformation solution at 4000r / min for 15min to remove bacterial cells, adjust the supernatant to pH 1.0 with 6mol / L hydrochloric acid, and heat to remove H 2 S, activated carbon decolorization, suction filtration, the filtrate was adjusted to pH 5.0 with 5mol / L NaOH, the L-cysteine ​​in the filtrate was oxidized by air, precipitated, vacuum suction filtration, washed with pure water, and dried to obtain 21g L-cysteine The crude amino acid was decoloriz...

Embodiment 3

[0044] 1. Add 18 g of tryptophan synthase wet thallus obtained by centrifuging 1000 mL of fermented liquid into 500 mL of transformation liquid, which contains 25 g / L L-serine hair acid hydrolyzate (total amino acid content 25%), 8 g of NaHS , 0.2g / L pyridoxal phosphate and 0.5g / L Tween-80, pH 9.0, enzymatic reaction at 25°C for 15h, the concentration of L-cysteine ​​in the conversion solution after the reaction was 23.8g / L - The molar conversion of serine is 82.6%.

[0045] 2. Centrifuge the transformation solution at 4000r / min for 15min to remove bacterial cells, adjust the supernatant to pH 1.0 with 6mol / L hydrochloric acid, and heat to remove H 2 S, decolorize with activated carbon, filter with suction, adjust the pH of the filtrate to 5.0 with 5mol / L NaOH, oxidize the L-cysteine ​​in the filtrate dropwise with hydrogen peroxide, precipitate out, filter with vacuum, wash with pure water, and dry to obtain 10.5g Crude L-cystine was decolorized by acid solution, neutralized...

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Abstract

The invention belongs to the field of biological technology and in particular relates to a method for preparing L-cysteine through enzymatic conversion. The preparation method comprises the following steps of: mixing wet thallus with synthetase activity or crude enzyme liquid and mixed amino acid liquid containing L-serine, wherein the mixed amino acid liquid containing the L-serine serves a raw material; adding a proper amount of hydrosulfide or sulfide; performing enzymatic reaction under the conditions of temperature of between 25 and 55 DEG C and pH value of 6 to 11; introducing air or adding hydrogen peroxide dropwise into the L-cysteine generated by the reaction and oxidizing; separating by an isoelectric point crystallization method to obtain L-cystine; and performing electrolytic reduction to prepare the L-cysteine. According to the method, the problem of difficulty in separation and comprehensive utilization of the L-serine in the mixed amino acid liquid is solved; and the L-cysteine product with high additional value is obtained. The method has the advantages of wide material sources, low price, simplicity and convenience in operation, short enzymatic synthesis time, low production cost and the like.

Description

1. Technical field [0001] The invention belongs to the field of biotechnology, and in particular relates to an enzymatic conversion preparation method of L-cysteine. 2. Background technology [0002] L-cysteine ​​is an amino acid that exists in nature and is also one of the non-essential amino acids for the human body. The sulfhydryl group it carries has important physiological functions. L-cysteine ​​and its derivatives can be used in the fields of medicine, cosmetics, food and feed additives, etc., and have a very wide range of applications. [0003] According to current literature reports, the preparation methods of L-cysteine ​​mainly include extraction method, chemical synthesis method, fermentation method and enzymatic conversion method. [0004] 1. Extraction method [0005] At present, the domestic production of L-cysteine ​​mainly uses human or animal hair as raw material. First, L-cysteine ​​is extracted by acid hydrolysis, and then L-cysteine ​​is obtained by el...

Claims

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Application Information

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IPC IPC(8): C12P13/12
Inventor 焦庆才刘均忠刘茜肖国安王先兵曾庆群
Owner NANJING UNIV
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