Improvement Of Streptococcus Suis Glutamate Dehydrogenase Expression In Escherichia Coli Through Genetic Modification Of Acetate Synthesis Pathway

Escherichia coli generates acetate as an undesirable by-product that has several negative effects on protein expression, and the reduction of acetate accumulation by modifying genes of acetate synthesis pathway can improve the expression of recombinant proteins. In the present study, the effect of phosphotransacetylase (pta) or/and acetate kinase (ackA) deletion on glutamate dehydrogenase (GDH) expression was investigated. The results indicated that the disruptions of pta or/and ackA decreased the acetate accumulation and synthesis of per gram cell, and increased cell density, and GDH expression and synthesis of per gram cell. The pta gene was more important for acetate formation than the ackA gene. Using the strain with deletions of pta-ackA (SSGPA) for GDH expression, acetate accumulation (2 center dot 61 g l(-1)) and acetate synthesis of per gram cell (0 center dot 229 g g(-1)) were lowest, decreasing by 28 center dot 29 and 41 center dot 43% compared with those of the parental strain (SSG) respectively. The flux of acetate synthesis (6 center dot 6%) was decreased by 72 center dot 15% compared with that of SSG, and the highest cell density (11 center dot 38 g l(-1)), GDH expression (2 center dot 78 mg ml(-1)), and GDH formation of per gram cell (0 center dot 2442 mg mg(-1)) were obtained, which were 1 center dot 22-, 1 center dot 43- and 1 center dot 17-times higher than the parental strain respectively. Significance and Impact of the Study