title: Metabolic engineering of microbes for branched-chain biodiesel production with low-temperature property.
abstract: BACKGROUND
  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. 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.
  
  
  RESULTS
  Inspired 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.
  
  
  CONCLUSIONS
  We 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.
authors.affiliation: Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education and Wuhan University School of Pharmaceutical Sciences, Wuhan, 430071 China ; Hubei Engineering Laboratory for Synthetic Microbiology, Wuhan Institute of Biotechnology, Wuhan, 430075 China.
authors.forename: Hui
authors.initials: H
authors.lastname: Tao
authors.affiliation: Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education and Wuhan University School of Pharmaceutical Sciences, Wuhan, 430071 China.
authors.forename: Daoyi
authors.initials: D
authors.lastname: Guo
authors.affiliation: Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education and Wuhan University School of Pharmaceutical Sciences, Wuhan, 430071 China ; Hubei Engineering Laboratory for Synthetic Microbiology, Wuhan Institute of Biotechnology, Wuhan, 430075 China.
authors.forename: Yuchen
authors.initials: Y
authors.lastname: Zhang
authors.affiliation: Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education and Wuhan University School of Pharmaceutical Sciences, Wuhan, 430071 China ; Hubei Engineering Laboratory for Synthetic Microbiology, Wuhan Institute of Biotechnology, Wuhan, 430075 China ; State Key Laboratory of Microbial Metabolism, School of Life Sciences and Biotechnology, Shanghai Jiao Tong University, 800 Dongchuan Road, Shanghai, 200240 China.
authors.forename: Zixin
authors.initials: Z
authors.lastname: Deng
authors.affiliation: Key Laboratory of Combinatorial Biosynthesis and Drug Discovery, Ministry of Education and Wuhan University School of Pharmaceutical Sciences, Wuhan, 430071 China ; Hubei Engineering Laboratory for Synthetic Microbiology, Wuhan Institute of Biotechnology, Wuhan, 430075 China ; Hubei Provincial Cooperative Innovation Center of Industrial Fermentation, Wuhan, 430068 China.
authors.forename: Tiangang
authors.initials: T
authors.lastname: Liu
keywords: Biodiesel; Branched-chain amino acid biosynthesis; Branched-chain esters; E. coli; Metabolic engineering; Pichia pastoris; WS/DGAT