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目的 :利用大肠杆菌磷酸转乙酰基酶 (PTA)缺陷变株减少工程菌乙酸的产生 ,以利于工程菌高密度培养及外源蛋白表达。方法 :从E .coliBL2 1(DE3)出发筛选PTA变株 ,并对变株的特性进行研究。结果 :筛选得到 5株磷酸转乙酰基酶缺陷变株 ,变株的乙酸累积水平为亲株的 1/ 5左右 ,最大比生长速率为亲株的 2 / 3左右。各种有机酸 (乙酸、乳酸、丙酮酸和琥珀酸 )对BL2 1(DE3)及其变株生长影响的考察结果显示 ,有机酸对PTA变株的生长抑制曲线发生了一定变化 ,其中以乙酸影响的变化最为显著。低浓度乙酸对PTA变株的生长不但不具抑制作用反而具有刺激作用 ,而高浓度乙酸对变株生长的抑制作用也明显减弱。
OBJECTIVE: To reduce the production of acetic acid in the engineered bacteria by using Escherichia coli phosphotransacetylase (PTA) -deficient strains to facilitate high-density culture of engineered bacteria and the expression of foreign proteins. Methods: The strain of PTA was screened from E.coli BL21 (DE3), and the characteristics of the mutant were studied. Results: Five mutant strains of phosphotransacetylase were screened. The accumulated acetic acid level of the mutant strain was about 1/5 of that of the parent strain, and the maximum specific growth rate was about 2/3 of the parent strain. The effects of various organic acids (acetic acid, lactic acid, pyruvic acid and succinic acid) on the growth of BL21 (DE3) and its mutants showed that the growth inhibitory curves of organic acids against PTA mutants varied. Acetic acid The impact of changes the most significant. Low concentration of acetic acid not only does not inhibit the growth of PTA strain but has a stimulating effect, while the high concentration of acetic acid on the growth of mutants also significantly weakened.