Influence of Oenococcus oeni and Brettanomyces bruxellensis on Aged Wine Microbial Taxonomic and Functional Profiles
In the wine making process, the interactions between lactic acid bacteria (LAB), yeast and other wine microflora have an impact on the wine quality. In this study, we investigate the influence of the LAB Oenococcus oeni and the spoilage yeast Brettanomyces bruxellensis on the microbial community of a Cabernet Sauvignon wine. We generated metagenomic datasets from inoculations of three strains of B. bruxellensis, in combination with two O. oeni strains, one with and one without cinnamoyl esterase activity. This esterase activity releases hydroxycinnamic acids (HCAs) that can subsequently be processed by some B. bruxellensis strains able to generate off-flavor compounds. We evaluated the influence of the O. oeni and B. bruxellensis on the microbial taxonomic and functional potential profile, particularly regarding off-flavor formation due to HCAs. We found that the effect on the microbial profiles depends on i) the O. oeni and B. bruxellensis strains being combined and ii) the abundance they reach in the final wine, which depends on certain unidentified conditions. We confirmed that the potential of B. bruxellensis to produce off-flavor compounds from HCAs depends on the strain. Interestingly, the samples without microbial inoculants also had this potential, suggesting that native grape microbiota could also influence the levels of HCA. We also found that the presence of B. bruxellensis does not interfere with the malolactic fermentation of the evaluated O. oeni strains, which leads to a less acidic taste. We show that metagenomic approaches can help uncover the complex wine microbial community traits, such as flavor, impacted by the simultaneous presence of O. oeni and B. bruxellensis.