Proteomic insight into the beneficial effect of mannoproteins on Oenococcus oeni in wine malolactic fermentation

Oenococcus oeni is the main species of lactic acid bacteria (LAB) responsible for malolactic fermentation (MLF) in winemaking. MLF development can present difficulties because of the harsh, stressful conditions of wine. Yeast mannoproteins have been described as possible activators of O. oeni and MLF. This study investigated the proteomic response of O. oeni PSU-1 to the presence of yeast mannoproteins in wine like-medium (WLM). In the proteomic analysis, 956 proteins were identified, with 59 differentially expressed proteins (DEPs) when mannoproteins were added. Notably, carbohydrate metabolism and transport were activated, suggesting the use of the mannose oligosaccharides released from mannoproteins. Some of the DEP proteins identified have been associated with mannan recognition in other LAB. However, proteins associated with amino acid metabolism were relatively low in abundance in the presence of mannoproteins, indicating that the amino acid fraction of mannoproteins is not relevant to O. oeni metabolism under the studied conditions. Surprisingly, some stress response proteins, such as ClpP, cold-shock DNA-binding protein, and the citrate transporter MaeP, presented increased abundance. The roles of these proteins in the presence of mannoproteins require further investigation.