Influence of the malolactic fermentation on wine metabolomics or drastic metabolomics changes due to malolactic fermentation

Abstract

It is well known that lactic acid bacteria modify the wine volatile compound. However, very few data are available regarding metabolite changes that occurred during the malolactic fermentation (MLF). In order to have a clearer picture of the metabolic signature of the bacteria in wine during the MLF, we have analyzed the exometabolome before and after MLF of wine fermented with 6 different yeast strains and 2 different bacteria. To this purpose, metabolomics analyses were carried out by LC-TOF-MS. 

The PCA analyses of the metabolomics data clearly distinguish samples at the end of alcoholic fermentation from samples after malolactic fermentation and samples from co-inoculation. These results confirmed the impact of bacteria on wine metabolome but also underlined the fact that co-inoculation of bacteria with yeast in must does not result in the same wine than sequential inoculation, from a metabolite point of view. This result clearly indicates that both matrix (must or wine) and yeast bacteria interactions are responsible for the observed differences. A focus on the comparison of wine before and after malolactic fermentation conducted by the lactic acid bacteria VP41 revealed a clear cut difference between the wines as represented by PLS-DA. These results confirmed the drastic changes of the wines due to malolactic fermentation. Some of the compounds catabolised or synthesized by the bacteria during MLF allows to identify specific metabolic pathway involved during MLF such as for example glycosyl hydrolases, which convert flavonoid glycosides to the corresponding aglycones, and esterase, degrading methyl gallate, tannins, or phenolic acid ester.