Co-ordinated combination of Embden-Meyerhof-Parnas pathway and pentose phosphate pathway in Escherichia coli to promote L-tryptophan production

摘要

In this study,phosphoenolpyruvate and erythrose-4-phosphate are efficiently supplied by collaborative design of Embden-Meyerhof-Parnas(EMP)pathway and pentose phosphate(PP)pathway in Escherichia coli,thus increasing the L-tryptophan production.Firstly,the effects of disrupting EMP pathway on L-tryptophan production were studied,and the results indicated that the strain with deletion of phosphofructokinase A(i.e.,E.coli JW-5ΔpfkA)produced 23.4±2.1 g/L of L-tryptophan production.However,deletion of phosphofructokinase A and glucosephosphate isomerase is not conducive to glucose consumption and cell growth,especially deletion of glucosephosphate isomerase.Next,the carbon flux in PP pathway was enhanced by introduction of the desensitized glucose-6-phosphate dehydrogenase(zwf)and 6-phosphogluconate dehydrogenase(gnd)and thus increasing the L-tryptophan production(i.e.,26.5±3.2 g/L vs.21.7±1.3 g/L)without obviously changing the cell growth(i.e.,0.41 h^(-1) vs.0.44 h^(-1))as compared with the original strain JW-5.Finally,the effects of co-modifying EMP pathway and PP pathway on L-tryptophan production were investigated.It was found that the strain with deletion of phosphofructokinase A as well as introduction of the desensitized zwf and gnd(i.e.,E.coli JW-5 zwf243 gnd361ΔpfkA)produced 31.9±2.7 g/L of L-tryptophan,which was 47.0%higher than that of strain JW-5.In addition,the glucose consumption rate of strain JW-5 zwf243 gnd361ΔpfkA was obviously increased despite of the bad cell growth as compared with strain JW-5.The results of this study have important reference value for the following application of metabolic engineering to improve aromatic amino acids producing strains.