PROBIEN   20416
INSTITUTO DE INVESTIGACION Y DESARROLLO EN INGENIERIA DE PROCESOS, BIOTECNOLOGIA Y ENERGIAS ALTERNATIVAS
Unidad Ejecutora - UE
congresos y reuniones científicas
Título:
Utilization of hexose sugars by patagonian Saccharomyces cerevisiae strains from oenological origin
Autor/es:
SIMES ADRIANA B.; CABALLERO ADRIANA C.; DEL MÓNACO SILVANA M.
Lugar:
Mar del Plata
Reunión:
Congreso; X Congreso Argentino de Microbiología General SAMIGE; 2014
Resumen:
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 sulphate 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 (m), 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 comparison. For
statistical analysis, ANOVA for multiple data comparison and post hoc tests (a= 0.05) were performed. Three strains were
selected from the growth curve profiles obtained, each showing tolerance to
must sugar concentration and with 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<0,05). Residual
sugars were analized evidencing total sugar consumtion by these strains, where
ÑIF8 depleted glucose from the media earlier than the commercial strain.
Molecular studies showed a significant higher expression of the HXT2 and HXT5
transporters in ÑIF8 and ÑNM16 strains (p<0,05), result that could explain
the improved performance of these yeasts in sugar utilization. Aditional
studies will allow to complete autocthonous strain characterization to validate
its use in wine fermentation. However, preliminar results suggest that Saccharomyces
cerevisiae strains from the Comahue region present a fermentative
metabolism best addapted to local agroecological conditions, evidenced by an
enhanced grape sugar consumption.