title: Membrane engineering via trans unsaturated fatty acids production improves Escherichia coli robustness and production of biorenewables.
abstract: Constructing microbial biocatalysts that produce biorenewables at economically viable yields and titers is often hampered by product toxicity. For production of short chain fatty acids, membrane damage is considered the primary mechanism of toxicity, particularly in regards to membrane integrity. Previous engineering efforts in Escherichia coli to increase membrane integrity, with the goal of increasing fatty acid tolerance and production, have had mixed results. Herein, a novel approach was used to reconstruct the E. coli membrane by enabling production of a novel membrane component. Specifically, trans unsaturated fatty acids (TUFA) were produced and incorporated into the membrane of E. coli MG1655 by expression of cis-trans isomerase (Cti) from Pseudomonas aeruginosa. While the engineered strain was found to have no increase in membrane integrity, a significant decrease in membrane fluidity was observed, meaning that membrane polarization and rigidity were increased by TUFA incorporation. As a result, tolerance to exogenously added octanoic acid and production of octanoic acid were both increased relative to the wild-type strain. This membrane engineering strategy to improve octanoic acid tolerance was found to require fine-tuning of TUFA abundance. Besides improving tolerance and production of carboxylic acids, TUFA production also enabled increased tolerance in E. coli to other bio-products, e.g. alcohols, organic acids, aromatic compounds, a variety of adverse industrial conditions, e.g. low pH, high temperature, and also elevated styrene production, another versatile bio-chemical product. TUFA permitted enhanced growth due to alleviation of bio-product toxicity, demonstrating the general effectiveness of this membrane engineering strategy towards improving strain robustness.
authors.affiliation: Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA.
authors.forename: Zaigao
authors.initials: Z
authors.lastname: Tan
authors.affiliation: Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA.
authors.forename: Jong Moon
authors.initials: JM
authors.lastname: Yoon
authors.affiliation: Chemical Engineering, School for Engineering of Matter, Transport, and Energy, Arizona State University, Tempe, AZ 85287-6106, USA.
authors.forename: David R
authors.initials: DR
authors.lastname: Nielsen
authors.affiliation: Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA.
authors.forename: Jacqueline V
authors.initials: JV
authors.lastname: Shanks
authors.affiliation: Department of Chemical and Biological Engineering, Iowa State University, Ames, IA 50011, USA. Electronic address: ljarboe@iastate.edu.
authors.forename: Laura R
authors.initials: LR
authors.lastname: Jarboe
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics; D004926:Escherichia coli / Q000235:genetics / Q000378:metabolism; D005231:Fatty Acids, Unsaturated; D060847:Metabolic Engineering; D011550:Pseudomonas aeruginosa / Q000201:enzymology / Q000235:genetics*; D019745:cis-trans-Isomerases / Q000096:biosynthesis / Q000235:genetics
chemical_list: D001426:Bacterial Proteins; D005231:Fatty Acids, Unsaturated; D019745:cis-trans-Isomerases
keywords: Carboxylic acids production; Membrane fluidity; Membrane integrity; Tolerance; Trans unsaturated fatty acids (TUFA)