产γ-氨基丁酸的乳酸菌株筛选及诱变

γ-氨基丁酸(-γaminobutyric acid,GABA)是中枢神经系统一种重要的抑制性神经递质。本研究从鲜奶中分离得到1株高产GABA的乳酸菌株hjxj-01,经初步鉴定为短乳杆菌。实验结果表明,在含5%的L-谷氨酸钠的GYP培养基中,此乳酸菌产GABA最大积累浓度为7 g/L。在此基础上,又先后使用了紫外线和γ射线对出发菌株进行了诱变处理。以正突变率为标准确定诱变条件。30W的紫外灯下,距离45cm照射及照射时间50 s为紫外线诱变的较佳条件;60Co射线诱变的适宜剂量为300 Gy。诱变后得到1株突变菌株hjxj-08119,经连续传代12次,遗传性状稳定,平均GABA产量达到17 g/L,较出发菌株hjxj-01提高142.9%。

SCREENING AND MUTAGENESIS OF Lactobacillus brevis FOR BIOSYNTHESIS OF γ-AMINOBUTYRIC ACID

γ-aminobutyric acid(GABA) is a major inhibitory neurotransmitter in the central nervous system.In this study,a GABA-producing strain,hjxj-01,was isolated from the milk samples and identified as Lactobacillus brevis.In the GYP medium containing sodium glutamate,the highest GABA concentration accumulated by Lactobacillus brevis hjxj-01 is 7 g/L.The strain was treated with UV and()~(60)Co γ-rays.Based on high positive mutation rate,the final mutagenesis conditions were UV light 30W,irradiation distance 45cm,irradiation time 50s,and()~(60)Co γrays irradiation of 500 Gy.The mutant strain,hjxj-08119,was bred by GABA resistance selection.Cultured for 12 generations continually,the GABA-producing capacity of hjxj-08119 maintained stably.The fermentation results indicate that compared with the origin strain hjxj-01,the average yield of GABA by hjij-08119 is 17 g/L,which is 142.9% of the origin strain.