title: Fatty aldehydes in cyanobacteria are a metabolically flexible precursor for a diversity of biofuel products.
abstract: We describe how pathway engineering can be used to convert a single intermediate derived from lipid biosynthesis, fatty aldehydes, into a variety of biofuel precursors including alkanes, free fatty acids and wax esters. In cyanobacteria, long-chain acyl-ACPs can be reduced to fatty aldehydes, and then decarbonylated to alkanes. We discovered a cyanobacteria class-3 aldehyde-dehydrogenase, AldE, that was necessary and sufficient to instead oxidize fatty aldehyde precursors into fatty acids. Overexpression of enzymes in this pathway resulted in production of 50 to 100 fold more fatty acids than alkanes, and the fatty acids were secreted from the cell. Co-expression of acyl-ACP reductase, an alcohol-dehydrogenase and a wax-ester-synthase resulted in a third fate for fatty aldehydes: conversion to wax esters, which accumulated as intracellular lipid bodies. Conversion of acyl-ACP to fatty acids using endogenous cyanobacterial enzymes may allow biofuel production without transgenesis.
authors.affiliation: Matrix Genetics, Seattle, Washington, United States of America.
authors.forename: Brett K
authors.initials: BK
authors.lastname: Kaiser
authors.forename: Michael
authors.initials: M
authors.lastname: Carleton
authors.forename: Jason W
authors.initials: JW
authors.lastname: Hickman
authors.forename: Cameron
authors.initials: C
authors.lastname: Miller
authors.forename: David
authors.initials: D
authors.lastname: Lawson
authors.forename: Mark
authors.initials: M
authors.lastname: Budde
authors.forename: Paul
authors.initials: P
authors.lastname: Warrener
authors.forename: Angel
authors.initials: A
authors.lastname: Paredes
authors.forename: Srinivas
authors.initials: S
authors.lastname: Mullapudi
authors.forename: Patricia
authors.initials: P
authors.lastname: Navarro
authors.forename: Fred
authors.initials: F
authors.lastname: Cross
authors.forename: James M
authors.initials: JM
authors.lastname: Roberts
mesh_terms: D000444:Aldehyde Dehydrogenase / Q000378:metabolism; D000447:Aldehydes / Q000378:metabolism*; D056804:Biofuels; D000458:Cyanobacteria / Q000235:genetics / Q000378:metabolism*; D050745:Enoyl-(Acyl-Carrier Protein) Reductase (NADPH, B-Specific) / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis / Q000378:metabolism*; D015870:Gene Expression; D007700:Kinetics; D014885:Waxes / Q000378:metabolism
chemical_list: D000447:Aldehydes; D056804:Biofuels; D005227:Fatty Acids; D014885:Waxes; C001634:fatty aldehyde; D000444:Aldehyde Dehydrogenase; D050745:Enoyl-(Acyl-Carrier Protein) Reductase (NADPH, B-Specific)