以乙酸为碳源生长菌体的两阶段培养生产L-半胱氨酸合成酶

Two-stage cultivation of Pseudomonas sp.F12 for production of enzymes for L-cysteine synthesis with acetate as the carbon source for growth

假单胞菌F12能够将DL-2-氨基-△^2-噻唑啉4-羧酸（DL-2-amino-△^2-thiazoline-4-carboxylicacid，DL—ATC）转化为L-半胱氨酸。将该微生物转化过程分为以乙酸和氨为碳源和氮源的菌体生长阶段和利用DL—ATC诱导L-半胱氨酸合成酶产生阶段。考察了乙酸对菌体生长的影响以及菌体比生长速率对L-半胱氨酸合成酶诱导的影响。结果表明，当乙酸浓度大于4g／L时对菌体生长有显著抑制作用，乙酸的存在对L-半胱氨酸合成酶的诱导有抑制作用，菌体比生长速率较高时更有利于酶系的产生。在5L罐中进行的两阶段培养，最高体积酶活达到283U／mL，比优化前提高了150％，比分批培养提高了130％。

Pseudomonas sp. F12 had the ability to produce L-cysteine by bioconversion of DL-2-amino-A2-thiazoline-4- carboxylic acid （DL-ATC）. The whole culture process of L-cysteine synthetase （CS） production was divided into two stages ： for the growth stage, cells were grown on acetate and ammonium to form biomass ; for the induction stage, CS was induced by DL-ATC. The effects of acetic acid on cell growth and the specific growth rate on CS production were investiga- ted. The results indicated that low concentration of acetic acid （ below 4 g/L） did not appear to inhibit cell growth signifi- cantly. The presence of acetic acid inhibited the CS production. It tured out that higher specific growth rate in the growth stage led to higher CS activity. The volumetric activity achieved 283 U/mL in a 5 L bioreactor, which was enhanced almost 150% compared to that of the previous one and 130% compared to that of the batch culture.