产γ-PGA的菌种筛选及发酵条件的优化

Screening of strains producing γ-polyglutamic acid and optimization of its fermentation conditions

中文关键词:  γ-多聚谷氨酸  菌种  分离  鉴定  发酵条件

英文关键词:γ-polyglutamic acid  strain  isolation  identification  fermentation conditions

中文摘要:

      目的 从不同的豆类发酵食品中分离筛选产γ-多聚谷氨酸的高产菌株, 并优化其发酵条件。方法 通过菌株的分离初筛、形态观察、生理生化特性分析、DNA序列测定以及系统发育树分析鉴定菌株。经测定发酵曲线, 并设计以发酵温度、转速、装液量、接种量为试验因素的L9(34)正交试验优化其发酵条件。结果 菌株A5与枯草芽孢杆菌的特性相似, 由基因序列同源性比对结果可知, 该菌与菌株编号为FJ441062枯草芽孢杆菌的同源性最高, 达到99.0%, 所筛选的菌株A5鉴定为枯草芽孢杆菌。确定其适宜的发酵条件为: 温度30 ℃, 初始pH为6.0, 接种量2%, 转速200 r/min, 培养时间72 h。优化发酵条件后, γ-PGA产量为12.12 g/L。结论 枯草芽孢杆菌A5能够发酵产生γ-多聚谷氨酸, 培养条件对γ-多聚谷氨酸的产量影响很大。

英文摘要:

      Objective To isolate and screen high yield strains which produce γ-polyglutamic acid (γ-PGA) from different soybean fermentation foods, and optimize its fermentation conditions. Methods The strain was identified by preliminary screening, morphological observation, physiological and biochemical characteristics analysis, DNA sequencing and phylogenetic tree analysis. L9(34) orthogonal experiment was designed to optimize the fermentation conditions considering the factors of fermentation temperature, rotation speed, liquid volume and inoculation amount. Results The characteristics of strain A5 were very similar to those of Bacillus subtilis. DNA sequencing results showed that the homology of strain was the highest with that of the strain of Bacillus subtilis FJ441062, which reached 99%. Therefore, A5 strain was identified as Bacillus subtilis. The optimum culture conditions were as follows: temperature was 30 ℃, initial pH was 6.0, inoculation amount was 2%, shaking speed was 200 r/min, and culture time was 72 h. After optimizing the fermentation conditions, the yield of γ-PGA was 12.12 g/L. Conclusion Bacillus subtilis A5 can produce γ-PGA, and the effect of culture conditions on the production of γ-PGA is very notable.