一株非谷氨酸依赖型聚γ-谷氨酸高产菌株的鉴定与诱变育种

Identification and Simulation Mutation of a High-productive Strain of Poly (γ-glutamic acid) Independent of Glutamic Acid

摘要:

从发酵制品中分离到一株不依赖谷氨酸作为发酵底物的高产菌株PGA-N, 通过形态、生理生化试验和遗传学研究, 确定PGA-N为地衣芽胞杆菌(Bacillus licheniformis)。根据该菌株的产生环境, 设计了无L-谷氨酸发酵基础培养基, 并对该培养基进行了碳氮源优化和菌种诱变筛选。PGA-N经过亚硝基胍和紫外线诱变筛选后得一突变株——PGA-N-C10, 其γ-PGA的产量提高到8.82 g/L。实验还考察了搅拌转速与细胞生物量、γ-PGA产量以及γ-PGA分子量之间的关系, 在搅拌速度为400 r/min时, γ-PGA产率可高达11.00 g/L。

Abstract:

A high productive poly γ-glutamic acid (γ-PGA) strain PGA-N in a culture medium containing no L-glutamine was isolated from fermentation products. With the following identifications of colony morphology, physiological and biochemistry experiments, and genetics, the strain PGA-N was classified as a Bacillus licheniformis. According to the product environment, the base culture medium having no L-glutamine was simulated. In order to enhance the production of the strain PGA-N, the fermentation conditions, such as carbon source, nitrogen source, were optimized and the γ-glutamic acid production reached 5.16 g/L after getting the optimum formulation of this culture medium. PGA-N was mutagenized with combination of NTG and UV. A mutant PGA-N-C10 was screened which PGA production was increased from 5.16 g/L to 8.82 g/L. The study also investigated the effects of agitation speed on the cell biomass, γ-PGA production and the γ-PGA molecular weight. The γ-PGA yield of PGA-N-C10 was as high as 11.00 g/L when the agitation speed was 400 r/min.