UTILIZATION OF HEXOSE SUGARS BY PATAGONIAN Saccharomyces cerevisiae STRAINS FROM ENOLOGICAL ORIGIN.

SIMES, A. B.; CABALLERO, A. C.; DEL MÓNACO S. M.

Mar del Plata

Congreso; X Congreso de Microbiología General; 2014

Sociedad Argentina de Microbiología General

During winemaking, Saccharomyces cerevisiae yeast is the main responsible for turning grape sugars in alcohol and CO2. Since this species is mostly glucophilic, important amounts of fructose may remain at the end of the alcoholic fermentation (AF) and non desired sweet wines may finally be obtained. The objective of this work was to select authoctonous S. cerevisiae strains with a higher capacity for hexose consumption, particularly fructose. Eight strains of S. cerevisiae isolated from red winemaking in the Añelo region (years 2005/2006), Neuquén province, Patagonia Argentina (previously characterized as authoctonous by molecular methods) were evaluated in its ability to grow and consume sugars. Yeasts were grown in YNB broths (Yeast Nitrogen Base, with aminoacids and ammonium sulfate 0,67%) supplemented with 20% (p/v) glucose, 20% (p/v) fructose or a mixture of 10% (p/v) of both sugars. Fermentation progress, carried out at laboratory scale, was evaluated by weighting and growth parameters: maximum specific growth rate (μ), lag phase duration (l) and maximum CO2 produced (A), were calculated from each treatment by directly fitting CO2 production versus time to the reparametrized Gompertz equation. Residual sugars were analized by enzimatic kits and sugar tolerance was evaluated by drop-test assays. Aditionally, hexose transporters expression (Hxt1p to Hxt6p) was detected by RT-PCR. In all cases, assays using Saccharomyces cerevisiae EC1118, a commonly used comertial starter, were carried out as a comparison. For statistical analysis, ANOVA for multiple data comparison and post hoc tests (α = 0.05) were performed. Three strains were selected from the growth curve profiles obtained, each showing tolerance to must sugar concentration and presenting statistical differences on growth parameters in the different media: ÑIF8 as glucophilic strain, ÑNM16 as clear fructophilic strain and ÑNM10 as a strain preferring the sugar mixture (p