Different composition of mannoprotein extracts and their beneficial effects on Oenococcus oeni and wine malolactic fermentation

Malolactic fermentation (MLF) is a biochemical process in winemaking where lactic acid bacteria (LAB) convert L-malic acid into L-lactic acid and carbon dioxide, contributing to the deacidification and microbiological stability of wine. Oenococcus oeni, the main bacterium responsible for MLF, must deal with challenging conditions such as high ethanol concentrations, low pH values and low nutrient availability. In this study, the effects of commercial mannoprotein extracts derived from the yeast Saccharomyces cerevisiae on the MLF were investigated. Three commercial mannoprotein extracts were used to study the effects of different O. oeni strains on the MLF in wine-like media. The results revealed that the type and concentration of mannoproteins present in the extracts significantly influence the rate of L-malic acid consumption and the duration of MLF. The characteristics of the mannoproteins, such as their molecular weight, monosaccharide composition and protein content, varied among the products, affecting their ability to promote MLF. This study highlights not only the potential of mannoproteins to improve MLF but also the importance of the selection of an extract with adequate composition characteristics to benefit the process.