不同浓度外源乙酸钠对耐乙酸大肠埃希菌DA19代谢和关键酶酶活的影响

为研究外源乙酸钠对大肠埃希菌DA19生长代谢的影响,将该菌株在氮源限制基本培养基及添加不同浓度乙酸钠的氮源限制基本培养基中连续培养,测定稳态时生长代谢参数和胞内关键酶酶活。与MN培养基相比,葡萄糖比消耗速率和延胡索酸比生成速率随外源乙酸钠质量浓度增加而逐渐下降,丙酮酸比生成速率则随外源乙酸钠质量浓度增加而明显增加,而乙酸比生成速率则明显降低(除9 g/L乙酸钠外)。磷酸果糖激酶、异柠檬酸脱氢酶、异柠檬酸裂解酶、苹果酸脱氢酶、磷酸烯醇式丙酮酸羧化酶和乙酸激酶酶活随外源乙酸钠质量浓度增加而呈先下降后上升的趋势,而6-磷酸葡萄糖脱氢酶则随着外源乙酸钠质量浓度增加而逐渐降低。为了应对外源乙酸钠压力,大肠埃希菌DA19的生长代谢和中心代谢途径酶活都发生了明显改变。

Effect of Different Concentration Exogenous Sodium Acetate on Metabolism and the Key Enzyme Activity in the Acetate Tolerant Escherichia coli DA19

In order to study the effect of exogenous sodium acetate on the metabolism of E. coli DA19, the strain were continuously cultured in nitrogen limited defined media without as well as with different concentration of sodium acetate. The metabolic parameters and the activities of key enzymes at steady growth state were tested and determined. As compared with nitrogen limited defined medium, specific glucose consumption rate and specific fumarate production rate of E. coli DA19 decreased following with the increase of exogenous sodium acetate concentration, and specific pyruvate production rate increased following with the increase of exogenous sodium acetate concentration, while the specific production rate of acetic acid significantly decreased (except 9 g/L sodium acetate). The enzyme activities of phosphofructokinase, isocitrate dehydrogenase, isocitrate lyase, malate dehydrogenase, phosphoenolpyruvate carboxylase and acetate kinase increased and then decreased following with the increase of exogenous sodium acetate concentration. However, the enzyme activities of glucose-6-phosphate dehydrogenase decreased following with the increase of exogenous sodium acetate concentration. In response to the stress of exogenous sodium acetate, distinct changes in enzyme activities happened both in growth metabolism and center metabolic pathways of E. coli DA19.