为了提高杆菌肽补料发酵的效率,在50 L罐水平研究了pH耦合、间歇-罐压控制和间歇-溶氧(dissolved oxygen, DO)耦合等补料策略对杆菌肽合成的影响。pH耦合策略的杆菌肽效价为1 006 U/mL,但存在对数中后期因pH低于设定值而无法补入葡萄糖的问题。间歇-罐压控制策略的效价(1 118 U/mL)比pH耦合策略提高了11%,但也存在发酵后期补糖量与DO不匹配的问题。间歇-DO耦合策略克服了以上缺陷,糖对杆菌肽的转化率(YP/S)比间歇-罐压控制策略提高了22.7%。基于间歇-DO耦合补料策略并于24 h二次补入氮源后,其平均杆菌肽合成速率达到了40.67 U/(mL·h),杆菌肽效价峰值达到了1 220 U/mL。建立了基于细胞需求的综合碳-氮-氧因素的补料策略,为工业化补料发酵生产杆菌肽提供了重要参考。
In order to enhance the efficiency of bacitracin fed-batch fermentation, effects of pH coupling, intermittent feeding-tank pressure control, intermittent-dissolved oxygen (DO) coupling and other feeding strategies on bacitracin synthesis were investigated in a 50 L fermenter. The amount of bacitracin produced by pH coupling strategy was 1 006 U/mL. However, in middle and late stages of logarithmic growth, glucose could not be filled in due to pH below the set value. Although bacitracin produced by intermittent feeding-tank pressure control strategy was 11% higher than that of pH coupling strategy, it also had a problem of sugar-DO mismatched at late fermentation stage. The intermittent-DO coupling strategy overcame the above drawbacks, the conversion rate of sugar to bacitracin (YP/S) increased by 22.7% compared with that of intermittent feeding-tank pressure control strategy. Based on intermittent-DO coupling feeding strategy and secondary nitrogen source feeding at 24 h, the average bacitracin synthesis rate reached 40.67 U/(mL·h), and the peak value of bacitracin production reached 1 220 U/mL. Therefore, a feeding strategy based on comprehensive carbon-nitrogen-oxygen factor of cell demand is established, which provides an important reference for industrialized fed-batch fermentation to produce bacitracin.
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