GLUTATHIONE ADDITION IMPROVES Oenococcus oeni ADAPTATION TO STRESS CONDITIONS OF WINEMAKING PROCESS

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

San Miguel de Tucumán

Congreso; XII CONGRESO ARGENTINO DE MICROBIOLOGIA GENERAL; 2017

During wine-making process after alcoholic fermentation can take placethe malolactic fermentation (MLF). This secondary fermentation consists in the convertionof L-malic acid into L-lactic acid and it is an important step to obtain highquality wines. Oenococcus oeni is thebest adapted species and is almost exclusively used as starter culture of MLF. However,viability and malolactic activity of O. oeniin wine depend on its resistance to several stress factors such as low pH andhigh concentrations of ethanol. Glutathione (GSH) is a non-proteic tripeptidethat acts as an antioxidant and is considered a protective agent againstadverse environments. The objective of this study was to investigate ifglutathione addition can improve tolerance of O. oeni against stressful wine conditions. Two strains of O. oeni, X2L and Sb10, were culturedin MRS medium with and without GSH addition (5mM). These pre-cultures weresequentially inoculated in grape juice fermented by Saccharomyces cerevisiae mc2containing L-malic acid (3 g/L). Bacterial growth was followed by viable cellscounts and MLF was monitored using an enzymatic method. In addition, expressionlevels of mleA (malolactic enzyme), hsp18 (heat shock protein) and citE (citrate lyase) genes wereevaluated by RT-qPCR. In presence of GSH, both strains of O. oeni showed higher biomass after 48 h of incubation beinggreater the GSH effect for the strain Sb10. During the sequential inoculation infermented wines, O. oeni X2Land Sb10 showed higher viability and malolactic activity when were pre-adaptedwith GSH completing MFL at 4 days while cells pre-cultured without GSH were notable to remove of L-malic acid after 7 days. Moreover, in presence of GSHhigher expression level of mleA genewas found in correlation to better MLF of O.oeni cultures pre-adapted with GSH. Genes involved in stress response, hsp18 and citE, also showed differential expression in pre-cultures grown withGSH. In conclusion the GSH addition had a positive effect on O. oeni growth during preparation ofstarter cultures and this previous adaptation step was able to improve the MLFperformance of O. oeni when wasinoculated in wines. These findings demonstrate the protective role of GSHagainst stressful conditions related to wine-making process.