Abstract
BackgroundWax ester synthases (WSs) can synthesize wax esters from alcohols and fatty acyl coenzyme A thioesters. The knowledge of the preferred substrates for each WS allows the use of yeast cells for the production of wax esters that are high-value materials and can be used in a variety of industrial applications. The products of WSs include fatty acid ethyl esters, which can be directly used as biodiesel.ResultsHere, heterologous WSs derived from five different organisms were successfully expressed and evaluated for their substrate preference in Saccharomyces cerevisiae. We investigated the potential of the different WSs for biodiesel (that is, fatty acid ethyl esters) production in S. cerevisiae. All investigated WSs, from Acinetobacter baylyi ADP1, Marinobacter hydrocarbonoclasticus DSM 8798, Rhodococcus opacus PD630, Mus musculus C57BL/6 and Psychrobacter arcticus 273-4, have different substrate specificities, but they can all lead to the formation of biodiesel. The best biodiesel producing strain was found to be the one expressing WS from M. hydrocarbonoclasticus DSM 8798 that resulted in a biodiesel titer of 6.3 mg/L. To further enhance biodiesel production, acetyl coenzyme A carboxylase was up-regulated, which resulted in a 30% increase in biodiesel production.ConclusionsFive WSs from different species were functionally expressed and their substrate preference characterized in S. cerevisiae, thus constructing cell factories for the production of specific kinds of wax ester. WS from M. hydrocarbonoclasticus showed the highest preference for ethanol compared to the other WSs, and could permit the engineered S. cerevisiae to produce biodiesel.
Highlights
Wax ester synthases (WSs) can synthesize wax esters from alcohols and fatty acyl coenzyme A thioesters
Wax ester synthases (WSs) are promiscuous enzymes involved in wax ester synthesis from alcohols and acyl coenzyme As (CoAs) [5]
The selected five WSs are from A. baylyi ADP1, M. hydrocarbonoclasticus DSM 8798, R. opacus PD630, Mus musculus C57BL/6 and P. arcticus 273-4
Summary
Wax ester synthases (WSs) can synthesize wax esters from alcohols and fatty acyl coenzyme A thioesters. Natural wax esters are typically esters of long-chain fatty acids and long-chain alcohols [1]; due to their special properties, they have been widely used in lubricants, cosmetics, linoleum, printing inks, candles and polishes. Wax ester synthases (WSs) are promiscuous enzymes involved in wax ester synthesis from alcohols and acyl coenzyme As (CoAs) [5]. Various WSs have different preferences for substrates with varied chain length and their unspecificity has been used in several biotechnological applications for ester production, for example, jojoba-like wax esters and fatty acid ethyl esters. Depending on the substrate specificity of the WS, various mixtures of wax esters with specific chain-length composition can be generated, which have optimal chemical compositions for certain specialty markets. The types of wax esters synthesized by a specific WS are determined by the WS substrate preference and available substrates provided through the host’s metabolism
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