P99: Efficient odd straight chain free fatty acid production by metabolically engineered Escherichia coli

Microbial biosynthesis of free fatty acids (FFAs) can be achieved by introducing an acyl-acyl carrier protein thioesterase gene into E. coli. The engineered E. coli usually produces even chain FFAs. In this study, propionyl-CoA synthase (prpE) from Salmonella enterica was overexpressed in two efficient even chain FFAs producers, ML103 (pXZM12) strain carrying an acyl-ACP thioesterase gene from Umbellularia californica and ML103 (pXZ18) strain carrying the acyl-ACP thioesterase gene from Ricinus communis combined with supplementation of extracellular propionate. Reasonable amount of C11, C13 and C15 odd chain FFAs could be produced from glucose and propionate by these metabolically engineered E. coli strains. In order to further increase the production of odd chain FFAs we manipulated the initialization step of the fatty acid synthesis cycle. The β-ketoacyl-acyl carrier protein synthase III (KAS III, fabH) from various sources, such as Bacillus subtilis (bsfabH1), Bacillus subtilis (bsfabH2), Staphylococcus aureus (SafabH) and Streptomyces peucetius (spdpsC), were coexpressed with the propionyl-CoA synthase, in the ML103 strain without its native fabH. With these genetic manipulations, the highest total amount of odd straight chain FFAs reached 1200 mg/l, and the highest percentage of odd straight chain FFAs reached 85.1%.