Studying On β-Glycosidase Activity Of Oenococcus Oeni And Its Effect On Wine Aroma

Wine quality is predominantly affected by the color, taste and aroma, so aroma is one of the most important factors to evaluate wine quality. In winemaking, β-glucosidase derived from wine-related lactic acid bacteria(LAB), especially Oenococcus oeni(O.oeni) is the most important glycosidase, which can contribute to wine aroma by malolactic fermentation(MLF) through the hydrolysis of grape-derived aroma precursors. In this study, we chosed six O.oeni strains possessing important oenological characteristics, the β-glycosidase activities of these strains were investigated, and the potential of hydrolysis of wine aroma precursors during Malolactic Fermentation with some of these strains who possess higher activity was evaluated. Thus, this study is of great significance for wine aroma enhancement and sensory quality improvement.In this study, color culture medium and molecular method were employed for detecton of glucosidase-encoding genes firstly. Then, the quantitative determination and location in cell of β-glucosidase were studied by spectrophotometry with synthetic substrate(p-nitrophenyl-β-glucopyranoside, pNPG). On this basis, the β-glucosidase gene and phospho-β-glucosidase gene expression were analyzed with RT-qPCR technology. Finally, three strains were chose to study the influence of O.oeni on wine aroma during MLF, and then GC-MS analysis was used. The main results are as following:(1) Detection of enzymes on color plate and PCR detection showed that selected O.oeni strains can produce beta-glycosidase with hydrolysis activity.(2) The enzyme assays with synthetic glycoside(pNPG) showed that the glycosidase activities profiles are highly stain-dependant. And O.oeni CS-1b displayed the highest glycosidase activity of all the tested strains.(3) With RT-qPCR technology, enzyme localization assay showed that glucosidases are mainly intracellular form for all of these strains. And enzyme localization were connected with the species of enzymes, so we hypothesized that phospho-β-glucosidase is likely to exist in the parietal, and β-glucosidase is mainly exist in the cytoplasm.(4) MLF which started by tested strains could increase the varieties of volatile aroma, especially in experimental group, in which the MLF was started by O.oeni CS-1b. Aroma compounds are the richeset in the group of O.oeni CS-1b. The results suggested that O.oeni CS-1b could be used as a source of β-glycosidase during MLF, and could be developed to be a commercial starter culture.