Biotechnological improvements of bio-based fuels and lubricants: characterization of genes for branched chain fatty acids and mono-acyl esters

Abstract

<p>The goals of the research in this dissertation are to generate the fundamental technologies that can be used to improve the production and quality of vegetable-oil based biodiesel and biolubricants. Specifically, we sought to test the hypothesis that branched chain fatty acids (BCFAs) can substitute for unsaturated fatty acids in maintaining fluidityin an organism. Toward this goal, we examined the utility of two Bacillus keto-acyl synthase III (KASIII) coding genes (yhfB and yjaX) in producing BCFAs. In conducting this research it was necessary to examine if the E. coli KASIII gene (fabH) was essential for initiating fatty acid biosynthesis and whether the Bacillus KASIII genes are interchangeable with that of E. coli. This research found that Bacillus yhfB gene is expressed in the examined state of the wild type while the yjaX gene is expressed conditionally. yhfB gene can accumulate more anteiso and short chain fatty acids. Both yhfB and yjaX gene can make branched fatty acids in E. coli strain MH13. MH13 strain is livable at non-permissive 39°C in the presence of yhfB gene, indicating BCFAs are able to substitute for unsaturated fatty acids auxtrophy of MH13. Contrary to previous report, this research demonstrates that E. coli fabH gene is not essential. But there is a growth deficiency associated with this mutation. Bacillus yhfB gene can partially complement the growth deficiency. Another part of the dissertation was to study the biochemical and physiological functions of putative mono-acyl ester synthase genes, which can catalyze the reaction between acyl-CoA and alcohol to generate mono-acyl esters in Arabidopsis. The studies reported herein were designed to establish a system for testing the hypothesis that these genes catalyze the synthesis of mono-acyl esters with different substrate specificity or they are expressed at different stage of the development of the plant.</p>