微生物转化DL-ATC生产L-半胱氨酸菌种筛选及产酶条件研究

Screening of Strains for Microbial Transformation from DL-ATC to L-cysteine

以DL-2-氨基-△2-噻唑啉-4-羧酸(DL-2-amino-△2-thiazoline-4-carboxylic acid,DL-ATC)作为分离平板中的唯一氮源,从土样中筛选可将DL-ATC生物转化为L-半胱氨酸的微生物菌株,得到5株转化菌株GJx5、GJx7、TJ4、TJ6和TJ7,其中GJx7菌株的转化能力较高。当DL-ATC浓度为1%时,经微生物转化2 h,反应液中L-半胱氨酸含量可达68.3μg/ml。该菌株传代性能稳定,连续传8代后相对转化活力为95.4%。以GJx7菌株为试验菌株的产酶条件试验表明,较适培养基初始pH值为7.0,摇瓶装量为250 ml锥形瓶装50 ml培养基,产酶较佳的碳源和氮源分别为麦芽糖和酵母膏。在较佳产酶条件下,当DL-ATC浓度为1%时,转化液中L-半胱氨酸含量可达320.2μg/ml,较优化前提高4.7倍。

Microorganisms for bioconversion from DL-2-amino-Δ2-thiazoline-4-carboxylic acid （DL- ATC） to L-cysteine were isolated from above 20 soil samples, with DL-ATC as sole nitrogen source for isolated plate. Five bacterial strains of GJx5, GJx7, TJ4, TJ6 and TJ7 were screened out. The strain GJx7 was the most powerful, with the productivity 68. 3μg/ml of L-cysteine. The heredity for strain GJx7 was stable, and the relative activity for the eighth generator was 95.4%. The optimum conditions for enzyme production in strain GJx7 were as follows： the optimal pH for medium was 7.0, and the optimal loading amount was 50ml for 250ml shake flask. The optimal carbon source and nitrogen source were maltose and yeast extract, respectively. The productivity of L-cysteine was 320. 2μg/ml under the optimum conditions, with 4. 7 times compared to the contrast.