为实现高水平的大肠杆菌高密度培养,提升发酵法产L-色氨酸的生产效率,以大肠杆菌 TRTH为供试菌株,在初始发酵工艺的基础上,先后对发酵接种量和底物KH2PO4添加量各设置4个梯度进行发酵对比试验,并着重考察了底物KH2PO4添加量对菌体生长、产酸、磷酸盐消耗、糖酸转化率及副产物积累的影响。试验结果表明,在接种量为20%(体积分数),底物KH2PO4添加量为10 g/L时,最高菌体密度达到65.39 g/L,最终L-色氨酸产量为59.55 g/L,分别较优化前提高了45.99%和31.17%,发酵延滞期明显缩短,菌体生长迅速,原料利用率大幅提高,主要副产物积累量较低,发酵总体水平达到最优。为大肠杆菌高密度培养在L-色氨酸发酵中的应用提供了一个成本低、可行性高的新策略,同时为L-色氨酸发酵生产中底物磷酸盐的调控提供了参考。
The purpose of this study was to achieve the high cell density cultivation of Escherichia coli and improve the efficiency of L-tryptophan production. E. coli TRTH was used as the L-tryptophan producer. The fermentation experiments were carried out with 4 different amounts of seed culture inoculum and KH2PO4. The effect of KH2PO4 addition on cell growth, acid production, phosphate consumption, sugar and acid conversion, and by-product accumulation were analyzed. The results showed that with 20% (V/V) inoculum and 10 g/L of KH2PO4 , the cell density reached the highest (65.39 g/L), with the final L-tryptophan yield being 59.55 g/L. Comparing with the results before optimization, the lag phase of the fermentation was significantly shorter, which means cell growth was quicker. The utilization rate of raw materials was greatly increased, and the accumulation of the by-products was lowered, thus, the overall level of fermentation was improved. This finding provides a highly feasible new strategy for lowering cost for the high cell density cultivation of E. coli in L-tryptophan fermentation application. At the same time, it provides a reference for the developing regulations for phosphate in L-tryptophan fermentation.
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