title: Enhanced production of branched-chain fatty acids by replacing β-ketoacyl-(acyl-carrier-protein) synthase III (FabH).
abstract: Branched-chain fatty acids (BCFAs) are important precursors for the production of advanced biofuels with improved cold-flow properties. Previous efforts in engineering type II fatty acid synthase (FAS) for BCFA production suffered from low titers and/or the co-production of a large amount of straight-chain fatty acids (SCFAs), making it nearly impossible for further conversion of BCFAs to branched biofuels. Synthesis of both SCFAs and BCFAs requires FabH, the only β-ketoacyl-(acyl-carrier-protein) synthase in Escherichia coli that catalyzes the initial condensation reaction between malonyl-ACP and a short-chain acyl-CoA. In this study, we demonstrated that replacement of the acetyl-CoA-specific E. coli FabH with a branched-chain-acyl-CoA-specific FabH directed the flux to the synthesis of BCFAs, resulting in a significant enhancement in BCFA titer compared to a strain containing both acetyl-CoA- and branched-chain-acyl-CoA-specific FabHs. We further demonstrated that the composition of BCFAs can be tuned by engineering the upstream pathway to control the supply of different branched-chain acyl-CoAs, leading to the production either even-chain-iso-, odd-chain-iso-, or odd-chain-anteiso-BCFAs separately. Overall, the top-performing strain from this study produced BCFAs at 126 mg/L, comprising 52% of the total free fatty acids.
authors: Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, 1 Brookings Drive, Saint Louis, Missouri, 63130.
authors: Wen
authors: W
authors: Jiang
authors: Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, 1 Brookings Drive, Saint Louis, Missouri, 63130.
authors: Yanfang
authors: Y
authors: Jiang
authors: Division of Biological & Biomedical Sciences, Washington University in St. Louis, Saint Louis, Missouri.
authors: Gayle J
authors: GJ
authors: Bentley
authors: Division of Biological & Biomedical Sciences, Washington University in St. Louis, Saint Louis, Missouri.
authors: Di
authors: D
authors: Liu
authors: Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, 1 Brookings Drive, Saint Louis, Missouri, 63130.
authors: Yi
authors: Y
authors: Xiao
authors: Department of Energy, Environmental, and Chemical Engineering, Washington University in St. Louis, 1 Brookings Drive, Saint Louis, Missouri, 63130. fzhang@seas.wustl.edu.|Division of Biological & Biomedical Sciences, Washington University in St. Louis, Saint Louis, Missouri. fzhang@seas.wustl.edu.
authors: Fuzhong
authors: F
authors: Zhang
mesh_terms: D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase; D000123:Acetyltransferases / Q000235:genetics / Q000378:metabolism*; D004926:Escherichia coli / Q000201:enzymology* / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D054889:Fatty Acid Synthase, Type II / Q000235:genetics / Q000378:metabolism; D005227:Fatty Acids / Q000096:biosynthesis*; D060847:Metabolic Engineering / Q000379:methods*; D053858:Metabolic Networks and Pathways / Q000235:genetics
chemical_list: D029968:Escherichia coli Proteins; D005227:Fatty Acids; D000123:Acetyltransferases; C557158:fabH protein, E coli; D015099:3-Oxoacyl-(Acyl-Carrier-Protein) Synthase; D054889:Fatty Acid Synthase, Type II
keywords: BKD; FabH; branched-chain fatty acids; α-keto acids