Response of Oenococcus oeni to stressful conditions related to winemaking process

LUCÍA M. MENDOZA

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

CERELA-CONICET

During wine-making process, at the end of the alcoholic fermentation can take place the malolactic fermentation (MLF) conducted by some species of lactic acid bacteria. This secondary fermentation consists in the decarboxylation of L-malic acid to L-lactic acid and is desirable because decreases titratable acidity, which translates into a smoother taste. Also, MLF improves aroma and flavor complexity of wine as well as it increases microbial stability through the removal of a carbon source which can be utilized by spoilage microorganisms. Oenococcus oeni is the best adapted species and is almost exclusively used for the induction of MLF. However, due to poor nutritional and harsh conditions related to chemical composition of wine (low pH, high ethanol and SO2 concentrations) the bacterial growth and MLF are not always successfully achieved. For this reason and taking in count that MLF is a critical step to obtain wines of high quality is interesting for industry to select starter cultures able to carry out successfully the MLF during wine elaboration. In addition, recently there has been growing interest in characterizing O.oeni strains that are unique to particular geographical wine regions in order to preserve the regional identity or terroir of wines. Therefore is also important to characterize and to select autochthonous strains of O. oeni. In this exposition it will discuss about the MLF performance of different strainsof O. oeni from Northwest region of Argentina. Moreover, it will present the possible mechanisms used by O. oeni X2L (CRL1947) to survive and carry out the MLF in stressful conditions simulated by sequential inoculation after alcoholic fermentation. The stress response of the malolactic bacterium was evaluated by using a proteomic approach (2D-E) and RT-qPCR. In addition, it will analyze if glutathione addition could increase tolerance of O. oeni to wine conditions evaluating viability, gene expression and fatty acid composition of bacterial membrane. These studies will conduct to selection of O. oeni strains more adapted to stress conditions which could improve its MLF performance during wine-making process.