title: Improving fatty acid availability for bio-hydrocarbon production in Escherichia coli by metabolic engineering.
abstract: Previous studies have demonstrated the feasibility of producing fatty-acid-derived hydrocarbons in Escherichia coli. However, product titers and yields remain low. In this work, we demonstrate new methods for improving fatty acid production by modifying central carbon metabolism and storing fatty acids in triacylglycerol. Based on suggestions from a computational model, we deleted seven genes involved in aerobic respiration, mixed-acid fermentation, and glyoxylate bypass (in the order of cyoA, nuoA, ndh, adhE, dld, pta, and iclR) to modify the central carbon metabolic/regulatory networks. These gene deletions led to increased total fatty acids, which were the highest in the mutants containing five or six gene knockouts. Additionally, when two key enzymes in the fatty acid biosynthesis pathway were over-expressed, we observed further increase in strain △cyoA△adhE△nuoA△ndh△pta△dld, leading to 202 mg/g dry cell weight of total fatty acids, ~250% of that in the wild-type strain. Meanwhile, we successfully introduced a triacylglycerol biosynthesis pathway into E. coli through heterologous expression of wax ester synthase/acyl-coenzyme:diacylglycerol acyltransferase (WS/DGAT) enzymes. The added pathway improved both the amount and fuel quality of the fatty acids. These new metabolic engineering strategies are providing promising directions for future investigation.
authors.affiliation: Department of Chemical Engineering, University of Michigan, Ann Arbor, Michigan, United States of America ; School of Chemical Engineering and Technology, Tianjin University, Tianjin, P.R. China.
authors.forename: Fengming
authors.initials: F
authors.lastname: Lin
authors.forename: Yu
authors.initials: Y
authors.lastname: Chen
authors.forename: Robert
authors.initials: R
authors.lastname: Levine
authors.forename: Kilho
authors.initials: K
authors.lastname: Lee
authors.forename: Yingjin
authors.initials: Y
authors.lastname: Yuan
authors.forename: Xiaoxia Nina
authors.initials: XN
authors.lastname: Lin
mesh_terms: D004926:Escherichia coli / Q000201:enzymology / Q000235:genetics / Q000378:metabolism*; D029968:Escherichia coli Proteins / Q000235:genetics / Q000378:metabolism*; D005227:Fatty Acids / Q000378:metabolism*; D060847:Metabolic Engineering / Q000379:methods*
chemical_list: D029968:Escherichia coli Proteins; D005227:Fatty Acids