Fatty Acid Production by Enhanced Malonyl-CoA Supply in Escherichia coli

Abstract

The expression of exogenous genes encoding acetyl-CoA carboxylase (Acc) and pantothenate kinase (CoaA) in Escherichia coli enable highly effective fatty acid production. Acc-only strains grown at 37°C or 23°C produced an approximately twofold increase in fatty acid content, and additional expression of CoaA achieved a further twofold accumulation. In the presence of pantothenate, which is the starting material for the CoA biosynthetic pathway, the size of the intracellular CoA pool at 23°C was comparable to that at 30°C during cultivation, and more than 500mg/L of culture containing cellular fatty acids was produced, even at 23°C. However, the highest yield of cellular fatty acids (1100mg/L of culture) was produced in cells possessing the gene encoding type I bacterial fatty acid synthase (FasA) along with the acc and coaA, when the transformant was cultivated at 30°C in M9 minimal salt medium without pantothenate or IPTG. This E. coli transformant contained 141mg/L of oleic acid attributed to FasA under noninducible conditions. The increased fatty acid content was brought about by a greatly improved specific productivity of 289mg/g of dry cell weight. Thus, the effectiveness of the foreign acc and coaA in fatty acid production was unambiguously confirmed at culture temperatures of 23°C to 37°C. Cofactor engineering in E. coli using the exogenous coaA and acc genes resulted in fatty acid production over 1g/L of culture and could effectively function at 23°C.