Diversion of Fatty Acid Synthesis Pathway of Escherichia coli for Production of Long Chain Fatty Alcohol

Fatty alcohols are valuable chemical used in the industrial manufacturing of innumerable products as well as in transportation sector. Microbial fatty alcohol production can be achieved in E. coli through fatty acid synthesis pathway by diverting fatty acyl ACP towards alcohol in a two-step process where an acyl ACP reductase (AAR) converts fatty acyl ACP to fatty aldehyde and further an aldehyde reductase converts fatty aldehyde to fatty alcohol. The first step was achieved in this study via optimal expression of an AAR from Synechococcus elongatus in E. coli. For achieving second step an extensive in silico and in vivo analysis was undertaken to identify aldehyde reductase / aldehyde dehydrogenase that could play role in converting fatty aldehyde to fatty alcohol. We identified a long chain specific aldehyde reductase that converted long chain aldehyde to alcohol at much higher efficiency than other enzymes of similar category and characterized in terms of substrate specificity via enzyme kinetics. We further co-expressed cyanobacterial AAR along with newly characterized aldehyde reductase and produced significant amount of long chain fatty alcohols of C16-C18 chain length range. Importantly, we modulated endogenous pathway leading to membrane lipid formation and found 60% increase in fatty alcohol production. Our study provides the new insight that will accelerate the effort towards improvement and development of fatty alcohol production through microbial engineering.