大肠杆菌乙酸耐受株的代谢流分布

Metabolic Flux Distribution of Escherichia coli Mutant with Improved Acetate tolerance

通过在基本培养基中的连续培养 ,比较了大肠杆菌耐乙酸突变株 JL3碳源基本代谢流量分布与出发株 JM1 0 1的差异 ,发现随比生长速率的增大 ,两者进入磷酸戊糖途径的碳流增加 ,进入三羧循环的碳流减少。在相同的比生长速率下 ,突变株 JL3中分配于磷酸戊糖途径的碳流所占比例高于 JM1 0 1 ,在比生长速率 0 .62 6h-1 时 ,JL3进入磷酸戊糖途径的碳流占摄入碳流的 33.2 %,而 JM1 0 1只占 9.0 %。计算得到 JL3和 JM1 0 1关于 ATP的最大菌体得率为 1 0 .2 g/mol和 5 .68g/mol,维持系数为 64.5 mmol/( g·h)和 82 .3mmol/( g·h) ,表明 JL3的能量代谢效率高于 JM1

Quantitative information of cellular metabolic network is an important aspect in metabolic engineering. Escherichia coli JL3, a mutant of E.coli JM101, shows improved acetate tolerance as compared with the original strain. Continuous cultures of JM101 and JL3 were respectively conducted in a defined medium, and metabolic flux distribution was estimated on the basis of material balance and the stoichiometric relationship among the metabolic reactions. In both strains, with the increase in the specific growth rate the carbon fluxes to the phosphopentose pathway increased while those to the tricarboxylic acid cycle reduced. At the same specific growth rate, the normalized carbon flux partitioned to phosphopentose pathway was greater while that to tricarboxylic acid cycle was lower in JL3 than those respectively in JM101. For example, at the specific growth rate of 0.626h -1 , the fluxes to PP pathway and TCA cycle respectively accounted for 33.2% and 14.5% in JL3, and those in JM101 were respectively 9.0% and 18.5% . The maximum cell yield based on generated ATP, Y MAX ATP , for JL3 and JM101 were respectively estimated to be 10.2 g/mol and 5.68g/mol, and the maintenance coefficient, m ATP , were respectively 64.5 mmol/(g·h) and 82.3mmol(g·h). These datas suggest a higher efficiency of energy metabolism in the acetate tolerant mutant, JL3.