Overexpression of the OLE1 gene enhances ethanol fermentation by Saccharomyces cerevisiae

Abstract

The fermentation characteristics of Saccharomyces cerevisiae strains which overexpress a constitutive OLE1 gene were studied to clarify the relationship between the fatty acid composition of this yeast and its ethanol productivity. The growth yield and ethanol productivity of these strains in the medium containing 15% dextrose at 10 degrees C were greater than those of the control strains under both aerobic and anaerobic conditions but this difference was not observed under other culture conditions. During repeated-batch fermentation, moreover, the growth yield and ethanol productivity of the wild-type S. cerevisiae increased gradually and then were similar to those of the OLE1-overexpressing transformant in the last batch fermentation. However, the unsaturated fatty acid content (77.6%) of the wild-type cells was lower than that (86.2%) of the OLE1-recombinant cells. These results suggested that other phenomena caused by the overexpression of the OLE1 gene, rather than high unsaturated fatty acid content, are essential to ethanol fermentation by this yeast.

Yeast Δ12 Fatty Acid Desaturase: Gene Cloning, Expression, and Function

“…Total lipids were extracted from logarithmically growing cells (OD600 = 1.0 to 1.5) and were then methylated using 1% sulfuric acid in methanol at 90 C for 2 h. 26) The fatty acid methyl esters were analyzed by gas-liquid chromatography (GLC: GC-18A, Shimadzu, Japan) and gas chromatographymass spectrometry (GC-MS: QP5000, Shimadzu, Japan). A fatty acid methyl ester mixture for the lipid standards was purchased from Sigma (USA).…”

Progress in Metabolic Engineering of Saccharomyces cerevisiae

“…In fact, the final ethanol concentration reaches about 20% in sake mash (173). Genetic engineering has identified several factors which may contribute to the higher ethanol tolerance of sake yeast, such as ergosterol (127), unsaturated fatty acids (154,155), palmitoyl coenzyme A (palmitoyl-CoA) (251), trehalose (153), inositol (90), and L-proline (341). However, in many cases researchers merely showed that the deletion of a certain gene causes a decrease in ethanol tolerance (90,127).…”

Genetic Dissection of Ethanol Tolerance in the Budding Yeast Saccharomyces cerevisiae

“…So far, several studies have been carried out to identify the genes affecting ethanol tolerance in yeast by testing performance of the reference yeast strain that was genetically modified at different candidate genes under an ethanol stress condition (Inoue et al 2000;Kajiwara et al 2000;Takahashi et al 2001;Fujita et al 2006;van Voorst et al 2006). The candidacy of the genes was determined mainly according to the genes' involvement in the previously mentioned biochemical or physiological pathways.…”