Abstract
BackgroundThe steadily increasing demand for diesel fuels calls for renewable energy sources. This has attracted a growing amount of research to develop advanced, alternative biodiesel worldwide. Several major disadvantages of current biodiesels are the undesirable physical properties such as high viscosity and poor low-temperature operability. Therefore, there is an urgent need to develop novel and advanced biodiesels.ResultsInspired by the proven capability of wax ester synthase/acyl-coenzyme A, diacylglycerol acyltransferase (WS/DGAT) to generate fatty acid esters, de novo biosynthesis of fatty acid branched-chain esters (FABCEs) and branched fatty acid branched-chain esters (BFABCEs) was performed in engineered Escherichia coli through combination of the (branched) fatty acid biosynthetic pathway and the branched-chain amino acid biosynthetic pathway. Furthermore, by modifying the fatty acid pathway, we improved FABCE production to 273 mg/L and achieved a high proportion of FABCEs at 99.3 % of total fatty acid esters. In order to investigate the universality of this strategy, Pichia pastoris yeast was engineered and produced desirable levels of FABCEs for the first time with a good starting point of 169 mg/L.ConclusionsWe propose new pathways of fatty acid ester biosynthesis and establish proof of concept through metabolic engineering of E. coli and P. pastoris yeast. We were able to produce advanced biodiesels with high proportions FABCEs and BFABCEs. Furthermore, this new strategy promises to achieve advanced biodiesels with beneficial low-temperature properties.Electronic supplementary materialThe online version of this article (doi:10.1186/s13068-015-0270-7) contains supplementary material, which is available to authorized users.
Highlights
The steadily increasing demand for diesel fuels calls for renewable energy sources
The cloud points of isopropyl and 2-butyl soyate are −9 and −12 °C, while the cloud point of methyl soyate is 0 °C [32, 35]. Since both the fatty acid chain and the alcohol functionality contribute to the overall properties of a fatty acid ester molecule [33] and there are several studies which have reported the biosynthesis of branched-chain alcohols, such as isopropanol, isobutanol, and isoamylol, using branched-chain amino acid biosynthetic precursors in E. coli [36,37,38,39], here we present de novo biosynthesis of a higher proportion of fatty acid branched-chain esters (FABCEs), including fatty acid isobutyl esters (FAIBEs) and fatty acid isoamyl esters (FAIAEs), which can be achieved through combination of the branched-chain amino acid biosynthetic pathways and fatty acid biosynthetic pathways in E. coli (Fig. 1)
Each FABCE was confirmed by corresponding standards that were synthesized by esterification of authentic fatty acid standards and alcohols (Additional file 2)
Summary
The steadily increasing demand for diesel fuels calls for renewable energy sources. This has attracted a growing amount of research to develop advanced, alternative biodiesel worldwide. With rapidly diminishing reserves of petroleum and increasing concerns about climate change, the development of renewable fuels as alternatives to fossil fuels has become a worldwide priority. The predominant alternative fuels for transportation are corn ethanol and soybean biodiesel, but they cannot satisfy the increasing demands [1,2,3]. After the identification of a novel wax ester synthase/acyl-CoA, diacylglycerol acyltransferase (WS/ DGAT), which can synthesize fatty acid esters from alcohols and fatty acyl-CoAs [20, 21], this process became more popular. Several groups engineered Saccharomyces cerevisiae to produce FAEEs [25, 26], and Nielsen’s group achieved a FAEE production of 34 mg/L by chromosome engineering and achieved another 40 % increase in FAEE production by overexpression of two genes (ACB1 and gapN) [27]
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
