Correlations between microbial diversity, monomeric phenols, and biological parameters during spontaneous fermentation of Cabernet Sauvignon grapes obtained from rain-shelter cultivation

This study aimed to evaluate the effect of rain-shelter on microbial diversity in spontaneous fermentation of Cabernet Sauvignon wines, and the correlations of core microbial taxa with biological parameters and monomeric phenols, with an open-field mode as the control. Firstly, rain-shelter increased the contents of 2.6% alcohol, 6.8% glycerol, 10.3% malic acid and 20.3% catechins in resulting wines, respectively (P < 0.05). As fermentation advanced, bacterial diversity decreased and then increased, while fungal diversity decreased (P < 0.05), regardless of cultivation. Besides, significant correlations were identified between Acetobacter, Pseudonocardia, Leuconostoc, Starmerella, Aspergillus and Saccharomyces and biological properties and monomeric phenols. Finally, the functions of bacterial genes were predicted to be primarily related to carbohydrate and amino acid metabolisms; fungi were more abundant in glycolytic pathway, and coenzyme A biosynthesis fatty acid elongation pathway. Overall, this information provides important insights into the succession and metabolism of indigenous microbes mediated by rain-shelter.