β-glycosidase activities of Oenococcus oeni: Current state of research and future challenges

The lactic acid bacterium Oenococcus oeni is the most important species for the controlled malolactic fermentation (MLF) of wine and it is best known for its generally positive effect on the wine flavor. While the major impact of MLF is the reduction of acidity, the diverse metabolic side activities of O. oeni can exert significant influences on a wine's aroma profile. Of particular interest are glycosidase activities that catalyze the release of grape-derived aroma compounds such as terpenes. Many detailed studies conducted over the last decade revealed that O. oeni displays several glycosidase (glucosidase, xylosidase, arabinosidase and rhamnosidase) activities and that these activities indeed affect the complex wine aroma. Biochemical characterization of purified glycosidases from O. oeni led to vital insights into the mechanisms that can be made responsible, and gave further indications that could be helpful to explain the high strain-dependant variations on the molecular level. At present, O. oeni is probably one of the best studied organisms regarding its glycoside metabolism. Beyond its direct impact on wine making, this information is highly important to understand the beta-glycoside metabolism of LAB in general, as orthologues to the glycosidase genes from O. oeni can be found in several other LAB species.