摘要:
目的:筛选一株高产γ-聚谷氨酸(γ-PGA)的菌株,并优化其发酵条件。方法:从豆腐作坊周边土地取样,采用平板稀释涂布法,筛选高产γ-PGA的菌株,通过菌落形态、分子生物学方法对其进行鉴定;以γ-PGA产量为响应值,在单因素实验的基础上,以温度、pH、转速、底物浓度为实验因素,采用Box-Behnken法设计四因素三水平试验进行响应面优化,确定其产γ-PGA最佳发酵条件。结果:筛选获得一株高产γ-PGA的芽孢杆菌B-6578,鉴定为暹罗芽孢杆菌(Bacillus siamensis);通过单因素和响应面最终获得该芽孢杆菌发酵产γ-PGA的最佳条件为:温度37.5 ℃,pH7.48,转速240 r/min,底物浓度52.70 g/L,摇瓶发酵36 h,γ-PGA的产量达到24.82 g/L,γ-PGA转化率为47.10%,比优化前提高了25.19%。结论:采用响应面法优化得到的发酵条件方便可行,利于γ-PGA的进一步开发利用。
Abstract:
Objective:A strain with high-yield of the γ-PGA (γ-polyglutamic acid) was isolated and purified, and the fermentation conditions for the γ-PGA production were optimized. Methods:A strain of high-yield of γ-PGA production was isolated and identified from the soil around the tofu workshop, the strain was isolated and purified by plate dilution method, and then the strain was identified by the morphological and its 16S rDNA sequence. On the basis of single factor experiment, with temperature, pH, rotating speed and substrate concentration as experimental factors, the Box-Behnken method was adopted to optimize the fermentation conditions. Results:The strain was named as Bacillus siamensis. By the experiments of single factor and Box-Behnken design, the optimal culture conditions were as follows:Temperature 37.5℃, pH7.48, speed 240 r/min, substrate concentration 52.70 g/L, in the condition of shaking flask fermentation 36 h, γ-PGA yield was of 24.82 g/L, the substrate utilization of monosodium glutamate was 47.10%, increased by 25.19% than before optimization. Conclusion:It was convenient and feasible to optimize the fermentation conditions by the response surface method, which is beneficial to the further development and utilization of the γ-PGA.
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