Abstract
The increased demand and limited supply of energy have resulted in enthusiasm to find an alternative for petroleum. Ethanol and biodiesel as traditional biofuels exhibit some limitations. Previous microbial production of advanced biofuels has focused on gasoline substitutes. This work demonstrates the practical use of microbial fatty acid metabolism to biosynthesizing a 3-hydroxyl fatty acid methyl ester and possible C16 fatty acid alcohol (used as a jet fuel or biodiesel supplement) by combining the favorable thioesterase and fatty acid methyltransferase or fatty acid reductase.
In our study, the overexpression of genes encoding acyl-ACP thioesterase BTE from Umbellularia californica and 3-hydroxyl fatty acid methyltransferase PhcB from Ralstonia solanacearumin E. coli led to produce 3-hydroxyl dodecanoyl methyl ester (3-OH DDME) at the titer of 6µg/L using waste glycerol as the sole carbon source. Our results showed that PhcB as a novel methyltransferase can methylate 3-hydroxyl dodecanoic acid. Our results revealed BTE from Umbellularia californica could generate 3- hydroxyl fatty acid. Due to the insolubility of PhcB in E.coli, we hypothesized that a soluble form of this protein would aid in increasing the production of 3-OH DDME. Our results also showed weak gene expression by addition of lower concentration of inducer (isopropyl-β-D-1-thiogalactopyranoside) or lower temperature by decreasing the cell culture growth temperature to 15℃ after induction would improve the protein production, although the majority of the protein was still in the insoluble fraction.