Skorokhodova Alexandra Yu, Morzhakova Anastasiya A, Gulevich Andrey Yu, Debabov Vladimir G
Research Institute for Genetics and Selection of Industrial Microorganisms, 1-st Dorozhniy pr., 1, 117545 Moscow, Russia.
Research Institute for Genetics and Selection of Industrial Microorganisms, 1-st Dorozhniy pr., 1, 117545 Moscow, Russia.
J Biotechnol. 2015 Nov 20;214:33-42. doi: 10.1016/j.jbiotec.2015.09.003. Epub 2015 Sep 8.
Efficient succinate production in Escherichia coli is attained during anaerobic glucose fermentation in biosynthetic processes combining the reductive branch of the TCA cycle and the glyoxylate bypass. Pyruvate dehydrogenase (PDH) or pyruvate formate lyase (PFL) serves in E. coli as a source of acetyl-CoA, a substrate for the glyoxylate bypass. Depending on enzymes responsible for acetyl-CoA generation, the contribution of the glyoxylate bypass to the anaerobic succinate biosynthesis may vary to support redox balance resulting in diverse maximum achievable yield values. Anaerobic succinate biosynthesis from glucose was studied using E. coli strains with altered expression of genes encoding PFL and PDH. For acetyl-CoA formation by PFL, the yield of 1.32 mol succinate per mole of glucose was achieved with the theoretical value of 1.6 mol/mol. Involvement of PDH in anaerobic acetyl-CoA synthesis increased succinate yield up to 1.49 mol/mol, which is 89.8% of the predicted maximum (1.6(6) mol/mol). The maximum yield of 1.69 mol succinate per mol glucose, amounting to 98.8% of the stoichiometric maximum (1.71 mol/mol), was achieved with the strain possessing PDH as the primary anaerobic source of acetyl-CoA. During high cell density fermentation, the best engineered strain produced high amounts of succinate (570.7 mM) and only small quantities of acetate (11.9 mM).
在大肠杆菌中,通过将三羧酸循环(TCA)的还原分支与乙醛酸循环支路相结合的生物合成过程,在厌氧葡萄糖发酵期间可实现高效的琥珀酸生产。丙酮酸脱氢酶(PDH)或丙酮酸甲酸裂解酶(PFL)在大肠杆菌中作为乙醛酸循环支路底物乙酰辅酶A的来源。根据负责生成乙酰辅酶A的酶不同,乙醛酸循环支路对厌氧琥珀酸生物合成的贡献可能会有所变化,以支持氧化还原平衡,从而产生不同的最大可实现产量值。使用编码PFL和PDH的基因表达发生改变的大肠杆菌菌株,研究了从葡萄糖进行厌氧琥珀酸生物合成的过程。对于由PFL形成乙酰辅酶A的情况,每摩尔葡萄糖的琥珀酸产量达到1.32摩尔,理论值为1.6摩尔/摩尔。PDH参与厌氧乙酰辅酶A合成可使琥珀酸产量提高至1.49摩尔/摩尔,为预测最大值(1.6(6)摩尔/摩尔)的89.8%。以PDH作为主要厌氧乙酰辅酶A来源的菌株,每摩尔葡萄糖的琥珀酸最大产量达到1.69摩尔,占化学计量最大值(1.71摩尔/摩尔)的98.8%。在高细胞密度发酵过程中,最佳工程菌株产生了大量琥珀酸(570.7 mM),仅产生少量乙酸(11.9 mM)。