碳源对重组大肠杆菌两阶段发酵产丁二酸的影响

研究了在好氧培养基中分别添加不同碳源对两阶段发酵菌体生长、酶活及代谢产物分布的影响，结果表明添加4mmol/L葡萄糖和12，54，80mmol/L乙酸钠均可以提高好氧阶段的菌体密度和相关酶活。将不同条件下培养的菌体转接厌氧发酵后，厌氧阶段的酶活和代谢产物分布也发生改变。进一步对酶活及代谢产物分析表明：Escherichia coli NZN111(sfcA)厌氧发酵过程中，磷酸烯醇式丙酮酸羧化激酶(PCK)是产丁二酸的关键酶，丙酮酸激酶(PYK)主要和副产物丙酮酸的积累有关，异柠檬酸裂解酶(ICL)对丁二酸产量也有一定影响。好氧培养基中添加80mmol/L乙酸钠，厌氧发酵结束时丁二酸的质量收率可达89.0%，相比对照提高了16.6%。

Effects of Carbon Sources on Succinate Production by Dual-phase Fermentations of Recombinant Escherichia coli

The effects of different carbon sources added to aerobic medium on cell growth, enzyme activity and metabolite distribution was investigated in dual-phase fermentations. The results showed that both cell density and enzyme activity were enhanced by adding 4mmol/L glucose or 12,54,80mmol/L sodium acetate to aerobic medium, respectively. Then centrifugated cells that had grown aerobically in different conditions were transferred to anaerobic fermentation, the enzyme activity and metabolite distribution changed. To analyze the anaerobic enzyme activity and metabolite distribution, it was concluded that during the anaerobic fermentation of Escherichia coli NZN111 overexpressed malic enzyme, PEP carboxykinase(PCK) was the key enzyme of succinate production, pyruvate kinase(PYK) was associated to the accumulation of by product pyruvate, and isocitrate lyase(ICL) have some influence on the concentration of succinate. The yield of succinate in anaerobic stage could reach 89.0%, which was 16.6% higher than that of the control by adding 80mmol/L sodium acetate as carbon source in aerobic medium.