Understanding Wine Yeast Strain Variation Using a Combined Lipidomic, Metabolomic, and Transcriptomic Approach
Ayca Ozcan, Melanie Massonnet, Biplab Paul,
Larry Lerno, Ben Montpetit, Dario Cantu, Anita Oberholster, and
David Block*
*University of California Davis, One Shields Ave., Davis, CA
95616 (deblock@ucdavis.edu)
Under identical fermentation conditions, wine yeast (Saccharomyces cerevisiae) strains demonstrate variation in cell biomass formation. Yeast strains that yield higher biomass can complete sugar depletion more efficiently than lower biomass-yielding strains. To understand this variation in nutrient utilization efficiency (NUE), we used a multifaceted approach to assess the metabolic and regulatory differences among yeast strains. In this study, four commercial wine yeast strains with varying NUE, Montrachet, Cote des Blanc, T306, and Uvaferm 43, were fermented in synthetic MMM medium under identical anaerobic fermentation conditions. The maximum cell concentration measured by absorbance at 600 nm varied from 7.4 to 10.2 among analyzed strains. Intracellular and extracellular metabolites were analyzed using GC-MS and HPLC-RI, respectively. Complete analysis of the phospholipid profile of each strain was performed using QqQ LC-MS. Moreover, a transcriptomics approach (RNA-Seq) was taken to understand relevant transcriptional control mechanisms. Partial least squares regression of metabolomic and lipidomic data show that certain metabolic pathways, including the pentose-phosphate pathway, TCA cycle, and fatty acid synthesis, are most relevant in determining NUE. Lipid profile analysis showed that while higher concentrations of phosphotidylcholine (PC) and phosphotidylethanolamine (PE) lipids in the yeast cell membrane correlate positively with higher biomass yields, higher concentrations of phosphotidylinositol (PI) lipids have the opposite relationship with biomass yield. Finally, analyzing gene expression levels using BINGO analysis identified genes related to cellular lipids, cofactors, and amino acid metabolic processes as most related to NUE.
Funding Support: The Ernest Gallo Endowed Chair in Viticulture and Enology
