Research On Low Emission Circulating Biotransformation Process For ?-alanine Production

In this paper,the perameters of L-aspartic acid a-decarboxylase enzymes(PanD)in recombinant Escherichia coli fermentation process was studied,YCY fermentation medium suitable initial pH value 7.5;Feeding formula and dosage are 9.52 g/L malt sugar and 15.6 g/L cose pulp,fed-batch process is better than single batch feeding,the fed-batch feeding time point are 3h?6h?9 h,71.4 g/L wort can replace the original YCY medium malt sugar used in the fermentation medium,use the fermentation tank to investigate the fermentation conditions of two different strain fermentation performance,the results show that the optimized fed-batch fermentation culture medium's effection is better than that of the original fermentation medium,enzyme activity increase 2 times.Secondly,optimization the transformation system conditions,the substrate concentration is 2 g/L,initial substrate pH value is 7,the transformation temperature is 35 ?.Study finds that increase dissolved oxygen can improve the PanD enzyme activity and substrate conversion,1%surface active agent X can promote substrate conversion rate by 87%,different inorganic ions have different effects on reaction conversion,Fe3+ can improve the substrate conversion rates 1.3 times.The 732 cation exchange resins were chosen to separate ?-alanine from aspartate by means of static and dynamic adsorption in the mixed liquid,process resin to H +type,when the resin adsorption time reach 15 min or above,two kinds of amino acid adsorption reached dynamic equilibrium,the optimum adsorption solution initial concentration is 15 g/L,pH 5,the best liquid adsorption temperature is 30 ?,the suitable ammonia washing concentration was 5%,considering the two kinds of resin adsorption method effect,in a follow-up experiment selection dynamic adsorption method.Finally,designed the low discharge circulating conversion reator,and studied on the cycle transformation system,the substrate feeding method is that in the former converting 48 h,every 8 h adding substrate concentration is 2 g/L,after that,each 8h add the substrate concentration is 1 g/L;surface active agent X has positive effect on PanD enzyme activity,and in the cycle transformation system it has no significant effect on enzyme stability;PanD enzyme half-life is 28.9 h,when circulating conversion react to the 24 h,the enzyme activity reaches a maximum value,reaction to the 48h,enzyme activity compared with the maximum value lower than half,after the 732 cation exchange resin were utilized for 5 batches in continuous adsorption,the adsorption amount of L-Asp and beta-Ala were decreased by 70%and 25%than the initial adsorption capacity,adding lOg resin to each 150mL loop transformation liquid in a completion cycle of transformation reaction system,the production of beta-Ala in cyclic reaction conversion system increased 1.55 times compared to it in batch conversion,Circulating conversion reaction system reduces the cost of production,and solve the follow-up product separation operation problem.