Effect of Modulated Glucose Uptake on High‐Level Recombinant Protein Production in a Dense Escherichia coli Culture

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Abstract
Methyl α‐glucoside (α‐MG) is a metabolically inert glucose analog sharing the same phosphotransferase system with glucose. The potential of using this compound, which acts as a nontoxic competitive inhibitor, to modulate glucose uptake and subsequently reduce the acetate accumulation rate was investigated. In a complex medium, no significant effect on the growth rate was observed when the α‐MG to glucose ratio was low. The effect of α‐MG supplementation on the production of a model recombinant protein, CadA‐β‐galactosidase, under the regulation of a pH‐inducible promoter in a batch culture was also examined. It was observed that the amount of acetate accumulation was drastically reduced in the presence of α‐MG. More importantly, recombinant protein productivity was significantly improved. A very high volumetric productivity of approximately 1.6 g/L recombinant protein in a dense culture with an OD600 of 35 was obtained in a simple batch fermentation. Even at this high cell density, the specific protein productivity was maintained at a high level and was estimated to account for about 40% of the total cellular protein.