Bacillus macorous合成γ-CGT酶过程中阻遏效应与指数流加发酵

Application of Exponential Fed-batch Model for Reducing Repression during γ-CGTase Production by Bacillus macorous

考察了不同搅拌转速、pH值和温度条件下,细胞生长、γ-CGT酶产量与培养液中直链麦芽低聚糖积累的关系.细胞的最大比生长速率为0.2h-1是γ-CGT酶产量从增长到下降的拐点.发酵液中直链麦芽低聚糖的存在能促进细胞生长并引起胞内的FDP,ATP和G6P含量增加,而对产酶显示出分解代谢阻遏效应.指数流加结果显示,通过限制细胞的比生长速率,可将阻遏作用控制在较低水平,酶产量得到了大幅度提高,是分批发酵酶产量的7.9倍,达到2565U/mL.

The Influences of agitation speed, temperature and pH-controlling strategy on cell growth, linear maltooligosaccharides accumulation in broth and γ-CGTase yield were investigated in the batch culture of Bacillus macorous. When the maximal value of specific growth rate was higher than 0.2 h^-1, the γ-CGTase yield decreased. The linear maltooligosaccharides generated during fermentation can promote the cell growth and elevate the intracellular contents of FDE ATP and G6P, which demonstrated a repression effect on the production of γ-CGTase. Hence, the exponential feeding mode of nutrients was carried out to control the catabolite repression by limiting the specific cell growth rate. The highest yield of γ-CGTase obtained in fed-batch was 2 565 U/mL, which was 7.9 times of that in batch fermentation.