Yeast and bacterial inoculation practices influence the microbial communities of barrel-fermented Chardonnay wines

Background and Aims During winemaking, alcoholic and malolactic fermentations are usually conducted by strains ofSaccharomyces cerevisiaeandOenococcus oeni, respectively. Although most commercial wines are produced via inoculation with both yeast and bacteria, uninoculated fermentations can increase microbial diversity, leading to more complex wines. In this study, Chardonnay must was subjected to a combination of inoculation treatments withS. cerevisiaeandO. oeniin order to investigate how yeast and bacterial inoculation may impact the microbial communities of these wines. Methods and Results Yeast and bacterial community dynamics, andS. cerevisiaeandO. oenipopulations, were monitored at different fermentation stages. Yeast inoculation practices altered the yeast community andS. cerevisiaestrains; wines left uninoculated had a higher diversity ofS. cerevisiaestrains and contained an increased abundance ofTorulaspora delbrueckii. The inoculatedO. oenistrain dominated the treatments to which it was added, but the uninoculated wines contained uniqueO. oenipopulations, including potentially indigenous dominant strains. Conclusions Uninoculated wines contained a greater diversity of yeast and bacteria than inoculated wines, including more indigenous/non-commercial species and strains. Significance of the Study These results highlight the importance of identifying the entire microbial community in fermentations, at both the species and strain level.