EFFECT OF GLUTATHIONE IN ADAPTATION OF Oenococcus oeni TO WINE-LIKE CONDITIONS

LUCÍA M. MENDOZA; IVANA EMMERT; RAÚL R. RAYA

San Miguel de Tucumán

Simposio; V Simposio Internacional de Bacterias Lácticas (SIBAL); 2016

CERELA-CONICET

During wine-making process, the malolactic fermentation (MLF) is a critical step to obtain high quality wines. This secondary fermentation consists in the convertion of malic acid into lactic acid and it is desirable because decreases total acidity and improves the stability and sensorial characteristics of red wines. Among wine lactic acid bacteria, Oenococcus oeni is the best adapted species and is almost exclusively used for the induction of MLF. However, viability and malolactic activity of O.oeni in wine depend on its resistance to several stress factors such as low pH, ethanol and other inhibitory metabolites produced by yeasts. Glutathione is a non-proteic tripeptide that in its reduced form acts as an antioxidant through the thiol group of cysteine. In the last years, glutathione addition in foods is being considered for its role in stress protection. The aim of this work was to evaluate the potential protective role of glutathione on tolerance of different strains of O. oeni to wine conditions. Twenty one strains of O. oeni were cultured in MRS medium at 30 °C to evaluate their growth and malic acid consumption. Bacterial growth was followed by optical density (OD600nm)measurements and viable cells counts. The MLF was monitored using an enzymatic method. Glutathione was added to medium at a final concentration of 5 mM. To select the best strains as possible starter cultures of MLF it was evaluated growth parameters and malic acid consumption during 48 h in MRS medium. All selected strains of O. oeni showed higher biomass in presence of glutathione after 48 h of incubation. This positive effect on bacterial growth was greater for some strains (Sb1 and Sb10), especially for those with lower growth rate. When these strains pre-cultured with glutathione were inoculated in WLM (wine like medium) containing ethanol(12%) and L-malic acid (4g/L), it was observed that those strains that showed better growth in presence of glutathione could also improve their malolactic activity.The results of this study showed that glutathione addition has a positive effect on growth of different strains of O. oeni which would contribute in the biomass production for preparation of starter cultures. Further studies are needed to prove if glutathione can be used in a previous adaptation step in order to improvethe MLF performance during wine elaboration.