Interaction of Lactobacillus vini with the ethanol-producing yeasts Dekkera bruxellensis and Saccharomyces cerevisiae

Lactobacillus vini was recently described as a contaminant in industrial ethanol fermentations and its co-occurrence with Dekkera bruxellensis was noted. We investigated the growth characteristics of L. vini in cocultivation together with either Saccharomyces cerevisiae or D. bruxellensis. Lower cell numbers of both the yeasts and L. vini as well as a decrease in ethanol and lactate formation in mixed batch cultures compared with pure cultures were noted. L. vini formed cell aggregates (flocs) in all cultivation media with different shapes in Man–Rogosa–Sharpe and yeast extract–peptone–dextrose media. Flocs’ size and proportion of cells bound to flocs increased with increasing ethanol concentration. In coculture, formation of lactic acid bacteria–yeast cell aggregates consisting of a bacterial core with an outer layer of yeast cells was observed. L. vini–D. bruxellensis flocs had a bigger surface, due to cells protruding from the pseudomycelium. The involvement of mannose residues in the flocculation between L. vini and yeasts was tested. The presence of mannose induced deflocculation in a concentration-dependent manner. Less mannose was required for the deflocculation of D. bruxellensis as compared with S. cerevisiae.