(462d) Metabolic Engineering of E. Coli Species for Fatty Acid Biosynthesis Using Acetic Acid

Acetic acid (HAc) can be cheaply generated from syngas by microbial and chemical catalysts or acidogenic fermentation using organic wastes. This study focuses on utilization of HAc for fatty acid (precursor for biodiesel) production. Firstly, an E. coli strain containing plasmids with acyl-ACP thioesterase (TE) and acetyl-CoA carboxylase (Acc) is created, producing 1.5 g/L free fatty acid from glucose. Then, we overexpress two native HAc metabolism pathways (pta-ack and acs) in E. coli.  The results indicate that overexpression of the acs pathway significantly increases cell growth in the presence of acetate, while knock-out of poxB or pta gene impairs HAc-based cell growth. To synthesize free fatty acid using HAc, the acs pathway and TE are overexpressed and the fadE gene involved in fatty acid degradation is deleted. The engineered strain achieves ~0.5 g/L free fatty acid from HAc in the shaking flask culture. To significant improve the titer of fatty acids, we build a fed batch experiment and employ a kinetic model to describe and simulate the fatty acid production using HAc as the main carbon source.