Cofactor Engineering for the Production of Short Chain Fatty Acid

Cofactor engineering for the production of short chain fatty acid

SongI Han, Ka-Yiu San

Department of Bioengineering, Rice University, Houston, TX

Free fatty acids can be used as precursors for the production of chemicals and biofuels. E. coli possesses the biosynthetic fatty acid pathway and the introduction of acyl-ACP thioesterase enables E. coli to produce free fatty acid with specific chain length in a substantial amount. In particular, many challenges have been proposed when producing short chain length free fatty acid in E. coli, which might be attributed to the toxicity, severe feedback inhibition, metabolic flux imbalance and so on. Thus, the respective studies with regard to the strategies proven to be helpful in the case of long chain free fatty acid accumulation need to be implemented independently to figure out the principles raveled in short chain free fatty acid production. Among a variety of approaches, the control of ratios of reducing equivalents appears to be important in that there are two steps to be involved in requiring cofactors such as NADPH or NADH in the elongation cycle of fatty acid biosynthesis. Enzymatic approaches can be plausible in E. coli bioprocessing system as a way of changing the cofactor ratios. For example, UdhA or PntAB, soluble pyridine nucleotide transhydrogenase or energy-dependent membrane-bound transhydrogenase, respectively can contribute to improving NADPH availability. In addition, NADK is linked to regulating the concentration of intracellular NAD+ and NADP+. In this study, cofactor engineering with UdhA, PntAB, and NADK in terms of producing short chain length free fatty acid was explored in engineered E. coli with different copy number plasmids. Experimental results demonstrated the effectiveness of cofactor engineering in enhancing the accumulation of short chain length free fatty acid.