Abstract
BackgroundMedium chain length (C6–C12) α,ω-dicarboxylic acids (DCAs) and corresponding esters are important building blocks for the polymer industry. For DCAs of 12 carbon atoms and longer, a sustainable process based on monooxygenase catalyzed ω-oxidation of fatty-acids has been realized. For medium-chain DCAs with a shorter chain length however, such a process has not been developed yet, since monooxygenases poorly ω-oxidize medium-chain fatty acids (MCFAs). On the contrary, esterified MCFAs are ω-oxidized well by the AlkBGTHJ proteins from Pseudomonas putida GPo1.ResultsWe show that MCFAs can be efficiently esterified and subsequently ω-oxidized in vivo. We combined ethyl ester synthesis and ω-oxidation in one-pot, whole-cell biocatalysis in Escherichia coli. Ethyl ester production was achieved by applying acyl-CoA ligase AlkK and an alcohol acyltransferase, either AtfA or Eeb1. E. coli expressing these proteins in combination with the ω-oxidation pathway consisting of AlkBGTHJ, produced mono-ethyl DCAs directly from C6, C8 and C9 fatty acids. The highest molar yield was 0.75, for mono-ethyl azelate production from nonanoic acid. Furthermore, di-ethyl esters were produced. Diethyl suberate was produced most among the di-ethyl esters, with a molar yield of 0.24 from octanoic acid.ConclusionThe results indicate that esterification of MCFAs and subsequent ω-oxidation to mono-ethyl DCAs via whole-cell biocatalysis is possible. This process could be the first step towards sustainable production of medium-chain DCAs and medium-chain di-ethyl esters.
Highlights
Medium chain length (C6–C12) α,ω-dicarboxylic acids (DCAs) and corresponding esters are important building blocks for the polymer industry
We investigated if the esterification module is able to esterify the mono-esterified DCAs (MEDAs) into di-esterified DCAs (DEDAs, Fig. 1b)
The ω-oxidation module system has been successfully tested before [6]. This system was expanded with AlkK and AtfA to realize the formation of esters
Summary
Medium chain length (C6–C12) α,ω-dicarboxylic acids (DCAs) and corresponding esters are important building blocks for the polymer industry. For DCAs of 12 carbon atoms and longer, a sustainable process based on monooxygenase catalyzed ω-oxidation of fatty-acids has been realized. For medium-chain DCAs with a shorter chain length such a process has not been developed yet, since monooxygenases poorly ω-oxidize medium-chain fatty acids (MCFAs). On the contrary, esterified MCFAs are ω-oxidized well by the AlkBGTHJ proteins from Pseudomonas putida GPo1
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