title: Engineering Saccharomyces cerevisiae fatty acid composition for increased tolerance to octanoic acid.
abstract: Biorenewable chemicals such as short and medium chain fatty acids enable functional or direct substitution of petroleum-derived building blocks, allowing reduction of anthropogenic greenhouse gases while meeting market needs of high-demand products like aliphatic alcohols and alpha olefins. However, producing these fatty acids in microorganisms can be challenging due to toxicity issues. Octanoic acid (C8) can disrupt the integrity of the cell membrane in yeast, and exogenous supplementation of oleic acid has been shown to help alleviate this. We recently engineered the Saccharomyces cerevisiae enzyme acetyl-CoA carboxylase by replacing serine residue 1157 with alanine to prevent deactivation by phosphorylation. Expression of Acc1S1157Ain S. cerevisiae resulted in an increase in total fatty acid production, with the largest increase for oleic acid. In this study, we evaluated the effect of this modified lipid profile on C8 toxicity to the yeast. Expression of Acc1S1157Ain S. cerevisiae BY4741 increased the percentage of oleic acid 3.1- and 1.6-fold in the absence and presence of octanoic acid challenge, respectively. Following exposure to 0.9 mM of C8 for 24 h, the engineered yeast had a 10-fold higher cell density relative to the baseline strain. Moreover, overexpressing Acc1S1157Aallowed survival at C8 concentrations that were lethal for the baseline strain. This marked reduction of toxicity was shown to be due to higher membrane integrity as an 11-fold decrease in leakage of intracellular magnesium was observed. Due to the increase in oleic acid, this approach has the potential to reduce toxicity of other valuable bioproducts such as shorter chain aliphatic acids and alcohols and other membrane stressors. In an initial screen, increased resistance to n-butanol, 2-propanol, and hexanoic acid was demonstrated with cell densities 3.2-, 1.8-, and 29-fold higher than the baseline strain, respectively. Biotechnol. Bioeng. 2017;114: 1531-1538. © 2017 Wiley Periodicals, Inc.
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine, California.
authors.forename: Pamela B
authors.initials: PB
authors.lastname: Besada-Lombana
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine, California.
authors.forename: Ruben
authors.initials: R
authors.lastname: Fernandez-Moya
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine, California.
authors.forename: Jacob
authors.initials: J
authors.lastname: Fenster
authors.affiliation: Department of Chemical Engineering and Materials Science, University of California, Irvine, California.
authors.forename: Nancy A
authors.identifier: 0000-0002-3570-0037
authors.initials: NA
authors.lastname: Da Silva
mesh_terms: D000103:Acetyl-CoA Carboxylase / Q000235:genetics* / Q000378:metabolism; D002210:Caprylates / Q000378:metabolism*; D002470:Cell Survival / Q000502:physiology*; D005227:Fatty Acids / Q000235:genetics / Q000378:metabolism*; D024861:Genetic Enhancement / Q000379:methods*; D012441:Saccharomyces cerevisiae / Q000166:cytology / Q000502:physiology*; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D002210:Caprylates; D005227:Fatty Acids; D029701:Saccharomyces cerevisiae Proteins; D000103:Acetyl-CoA Carboxylase; C031492:octanoic acid
keywords:  octanoic acid; Saccharomyces cerevisiae; acetyl-CoA carboxylase; membrane damage; oleic acid; toxicity