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 pr

Method used

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Examples

Experimental program
Comparison scheme
Effect test

Example Embodiment

[0037] Example one

[0038] 1. Add 18g of tryptophan synthase wet bacteria obtained by centrifugation of 1000mL fermentation broth to 500mL conversion solution. The conversion solution contains 38g / L L-serine hair acid hydrolysate (15% total amino acid content), 13g 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 solution is 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 the bacterial cells, adjust the pH of the supernatant to 1.0 with 6mol / L hydrochloric acid, and heat to remove H 2 S, activated carbon decolorization, suction filtration, the filtrate is adjusted to pH 5.0 with 5mol / L NaOH, the L-cysteine ​​in the filtrate is oxidized by air, the precipitate is precipitated, vacuum filtration, washing with pure water, and drying to obtain 16.8g L- Crude cystine, decolo...

Example Embodiment

[0040] Example two

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

[0042] 2. Centrifuge the transformation solution at 4000r / min for 15min to remove the bacterial cells, adjust the pH of the supernatant to 1.0 with 6mol / L hydrochloric acid, and heat to remove H 2 S, activated carbon decolorization, suction filtration, the filtrate is adjusted to pH 5.0 with 5mol / L NaOH, the L-cysteine ​​in the filtrate is oxidized by air, the precipitate is precipitated, vacuum filtration, washing with pure water, and drying to obtain 21g L-cysteine Crude acid, decolorized by acid, neu...

Example Embodiment

[0043] Example three

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

[0045] 2. Centrifuge the transformation solution at 4000r / min for 15min to remove the bacterial cells, adjust the pH of the supernatant to 1.0 with 6mol / L hydrochloric acid, and heat to remove H 2 S, activated carbon decolorization, suction filtration, the filtrate is adjusted to pH 5.0 with 5mol / L NaOH, the L-cysteine ​​in the filtrate is added dropwise to hydrogen peroxide to oxidize, the precipitate is precipitated, vacuum filtration, washing with pure water, and drying to obtain 10.5g Crude L-cystine,...

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PUM

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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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