13In the wine making process, the interactions between lactic acid bacteria (LAB), yeast and other 14 wine microflora have an impact on the wine quality. In this study, we investigate the influence of 15 the LAB Oenococcus oeni and the spoilage yeast Brettanomyces bruxellensis on the microbial 16 community of a Cabernet Sauvignon wine. We generated metagenomic datasets from inoculations 17 of three strains of B. bruxellensis, in combination with two O. oeni strains, one with and one 18 without cinnamoyl esterase activity. This esterase activity releases hydroxycinnamic acids (HCAs) 19 that can subsequently be processed by some B. bruxellensis strains able to generate off-flavor 20 compounds. We evaluated the influence of the O. oeni and B. bruxellensis on the microbial 21 taxonomic and functional potential profile, particularly regarding off-flavor formation due to HCAs. 22 We found that the effect on the microbial profiles depends on i) the O. oeni and B. bruxellensis 23 strains being combined and ii) the abundance they reach in the final wine, which depends on certain 24 unidentified conditions. We confirmed that the potential of B. bruxellensis to produce off-flavor 25 All rights reserved. No reuse allowed without permission.(which was not peer-reviewed) is the author/funder, who has granted bioRxiv a license to display the preprint in perpetuity.The copyright holder for this preprint . http://dx.doi.org/10.1101/216390 doi: bioRxiv preprint first posted online Nov. 8, 2017; compounds from HCAs depends on the strain. Interestingly, the samples without microbial 26 inoculants also had this potential, suggesting that native grape microbiota could also influence the 27 levels of HCA. We also found that the presence of B. bruxellensis does not interfere with the 28 malolactic fermentation of the evaluated O. oeni strains, which leads to a less acidic taste. We show 29 that metagenomic approaches can help uncover the complex wine microbial community traits, such 30 as flavor, impacted by the simultaneous presence of O. oeni and B. bruxellensis. 31 Keywords: Microbiome, metagenomics, Brettanomyces bruxellensis, Oenococcus oeni, malolactic 32 fermentation, alcoholic fermentation, hydroxycinnamic acids, off-flavor formation. 33 34 35
Wine-making and wine microbial interactions 36The study of the wine microbial ecosystem has mostly been focused on the two key fermentation 37 players, Saccharomyces cerevisiae, which performs the alcoholic fermentation (AF), and 38Oenococcus oeni, which performs the malolactic fermentation (MLF), although other genus and 39 species can also affect the wine characteristics. MLF is in fact a decarboxylation process where 40 dicarboxylic L-malic acid (malate) is converted to monocarboxylic L-Lactic acid (lactate) and CO2, 41 which can result in a rise in pH. Thus, MLF softens the acid structure of the wine, as L-lactic acid is 42 perceived as less acidic than L-malic acid. MLF usually starts spontaneously about 1-3 weeks after 43 completion of AF and lasts 2-12 weeks. Furthermore, som...