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Modular and selective biosynthesis of gasoline-range alkanes

Paper ID Volume ID Publish Year Pages File Format Full-Text
31474 44800 2016 13 PDF Available
Title
Modular and selective biosynthesis of gasoline-range alkanes
Abstract

•E. coli was engineered to selectively produce C3 through C9 alkanes.•Fatty acid synthesis chain elongation resulted in C7 and C9 alkane synthesis.•More theoretically efficient reverse beta-oxidation was used to make C3–C5 alkanes.•Use of AD_A122F from Nostoc punctiforme PCC73102 slightly improves synthesis.•ADs can catalyze conversion of branched FFA precursors into corresponding alkanes.

Typical renewable liquid fuel alternatives to gasoline are not entirely compatible with current infrastructure. We have engineered Escherichia coli to selectively produce alkanes found in gasoline (propane, butane, pentane, heptane, and nonane) from renewable substrates such as glucose or glycerol. Our modular pathway framework achieves carbon-chain extension by two different mechanisms. A fatty acid synthesis route is used to generate longer chains heptane and nonane, while a more energy efficient alternative, reverse-β-oxidation, is used for synthesis of propane, butane, and pentane. We demonstrate that both upstream (thiolase) and intermediate (thioesterase) reactions can act as control points for chain-length specificity. Specific free fatty acids are subsequently converted to alkanes using a broad-specificity carboxylic acid reductase and a cyanobacterial aldehyde decarbonylase (AD). The selectivity obtained by different module pairings provides a foundation for tuning alkane product distribution for desired fuel properties. Alternate ADs that have greater activity on shorter substrates improve observed alkane titer. However, even in an engineered host strain that significantly reduces endogenous conversion of aldehyde intermediates to alcohol byproducts, AD activity is observed to be limiting for all chain lengths. Given these insights, we discuss guiding principles for pathway selection and potential opportunities for pathway improvement.

Keywords
Alkanes; Gasoline; Biofuel; E. coli; Metabolic engineering; Synthetic biology
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Publisher
Database: Elsevier - ScienceDirect
Journal: Metabolic Engineering - Volume 33, January 2016, Pages 28–40
Authors
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Subjects
Physical Sciences and Engineering Chemical Engineering Bioengineering
Get Full-Text Now
Don't Miss Today's Special Offer
Price was $35.95
You save - $31
Price after discount Only $4.95
100% Money Back Guarantee
Full-text PDF Download
Online Support
Any Questions? feel free to contact us