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Improvement of Streptococcus suis glutamate dehydrogenase expression in Escherichia coli through genetic modification of acetate synthesis pathway
Author(s) -
Wang J.,
Shang Q.,
Zhao C.,
Zhang S.,
Li Z.,
Lin C.,
Shen Z.,
Cheng L.
Publication year - 2020
Publication title -
letters in applied microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.698
H-Index - 110
eISSN - 1472-765X
pISSN - 0266-8254
DOI - 10.1111/lam.13244
Subject(s) - streptococcus suis , escherichia coli , glutamate dehydrogenase , microbiology and biotechnology , biology , bacteria , glutamate receptor , streptococcus , enzyme , dehydrogenase , biochemistry , chemistry , gene , genetics , receptor , virulence
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 ( ack A) deletion on glutamate dehydrogenase (GDH) expression was investigated. The results indicated that the disruptions of pta or/and ack A 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 ack A gene. Using the strain with deletions of pta ‐ ack A (SSGPA) for GDH expression, acetate accumulation (2·61 g l −1 ) and acetate synthesis of per gram cell (0·229 g g −1 ) were lowest, decreasing by 28·29 and 41·43% compared with those of the parental strain (SSG) respectively. The flux of acetate synthesis (6·6%) was decreased by 72·15% compared with that of SSG, and the highest cell density (11·38 g l −1 ), GDH expression (2·78 mg ml −1 ), and GDH formation of per gram cell (0·2442 mg mg −1 ) were obtained, which were 1·22‐, 1·43‐ and 1·17‐times higher than the parental strain respectively. Significance and Impact of the Study Significance and Impact of the Study: Acetate is the key undesirable by‐product in Escherichia coli cultivation, and both biomass and production of desired products are increased by the reduction of acetate accumulation. In the present study, the strains with deletions of pta or/and ack A were constructed to reduce the acetate accumulation and improve the GDH expression, and the highest expression level of GDH was obtained using the strain with lesion in pta ‐ ack A that was 1·17‐times higher than that of the parental strain. The construction strategy of recombinant E. coli for decreasing the acetate excretion can be used for high expression level of other desired products.