Typical renewable liquid fuel alternatives to gasoline are not entirely compatible with current infrastructure. Building upon our recent strain engineering and pathway design work (J. Am. Chem. Soc. 136:11644-11654; Nat. Commun. 5:5031), we have now engineered Escherichia coli to selectively produce dominant alkanes found in gasoline (propane, butane, pentane, heptane, and nonane) from renewable substrates such as glucose or glycerol. Our modular pathway framework allows seamless exchange between fatty acid synthesis and reverse β-oxidation to achieve desired extension of carbon chain length. Free fatty acids are subsequently converted to alkanes using a carboxylic acid reductase and a cyanobacterial aldehyde decarbonylase. We achieve high individual selectivity by modifying and using enzymes that have greater activity on shorter substrates and by demonstrating accumulation of C4 to C8 aliphatic aldehydes in the context of alkane production using an engineered host strain (the E. coli RARE strain). The selectivity obtained by different module pairings provides a foundation for tuning alkane product distribution for desired fuel properties.

Biosynthesis of key gasoline-range alkanes using engineered E. coli

249th National Meeting (2015)

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