Expanding the Product Profile of a Microbial Alkane Biosynthetic Pathway

Abstract

Microbially produced alkanes are a new class of biofuels that closely match the chemical composition of petroleum-based fuels. Alkanes can be generated from the fatty acid biosynthetic pathway by the reduction of acyl-ACPs followed by decarbonylation of the resulting aldehydes. A current limitation of this pathway is the restricted product profile, which consists of n-alkanes of 13, 15, and 17 carbons in length. To expand the product profile, we incorporated a new part, FabH2 from Bacillus subtilis, an enzyme known to have a broader specificity profile for fatty acid initiation than the native FabH of Escherichia coli. When provided with the appropriate substrate, the addition of FabH2 resulted in an altered alkane product profile in which significant levels of n-alkanes of 14 and 16 carbons in length are produced. The production of even chain length alkanes represents initial steps toward the expansion of this recently discovered microbial alkane production pathway to synthesize complex fuels. This work was conceived and performed as part of the 2011 University of Washington international Genetically Engineered Machines (iGEM) project.

Microbial Engineering for Aldehyde Synthesis

“…A similar challenge of limiting unwanted flux from aldehyde intermediates to alcohol byproducts has been encountered in the context of alkane production. The final step to alkane biosynthesis features the conversion of a C n aldehyde to a C nϪ1 alkane catalyzed by an aldehyde decarbonylase or aldehyde deformylating oxygenase (26,(58)(59)(60)(61)(62). Although the problem of alcohol byproduct formation has been described extensively, very few studies of alkane biosynthesis have used strains engineered with deletions of aldehyde reductases.…”

Recent advances in biosynthesis of fatty acids derived products in Saccharomyces cerevisiae via enhanced supply of precursor metabolites

“…Although the success in engineering E. coli to produce alkanes with different chain lengths [10,25,28,55], there has been no report on the reconstitution of the cyanobacterial alkane pathways in yeast so far. The difficulty in the construction of an alkane producing yeast lies on the lack of free ACP and fatty acyl-ACPs in the cytosol, which are constrained in the type I FAS complex, since AAR showed much higher affinity and activity toward acyl-ACPs than acyl-CoAs [55].…”

Biosynthesis of odd-chain fatty alcohols in Escherichia coli

“…A few works have expanded free fatty acid (FFA) or alkane profile through manipulation of fabH gene in upstream fatty acids biosynthesis pathway (Harger et al, 2013;Howard et al, 2013;Wu and San, 2014). Microbial alkanes are normally odd chain length as the last reaction is decarbonylation that takes off one carbon from the intermediate fatty aldehydes (Lee et al, 2015) (Fig.…”