Effect of enzymatic extract (grape endophyte Alternaria sp. MG1) with β-glucosidase activity on wine aroma compounds, polyphenols and color

This study aimed to investigate the effects of endophyte MG1 enzyme extracts with β-glycosidase activity on the fermentation performance and quality of red wine. The results showed that five β-glycosidase-encoding genes were identified, which were classified into three subclasses, class I (Gglean002014.1, Gglean005948.1, and Gglean003820.1), class II (Gglean012638.1), class III (Gglean001392.1). The enzyme extracts prepared by culturing MG1 in commercial PDB medium had higher protein concentration and β-glycosidase activity than those in natural potato medium. When different enzyme extracts were added to the wine fermentation system, their activities all reached the maximum on day 4, ranging from 0.678∼0.766 μkat/L. Most treatments significantly increased the contents of tannins and flavanols (EXT2), but decreased the contents of total flavonols (INT1 and EXT1) and total phenols (EXT1 and INT2). The INT1 treatment significantly increased the content of acetate esters; meanwhile, most fatty acid ethyl esters, ethyl acetate, isoamyl acetate, phenylethyl alcohol, and phenylethyl acetate were distributed close to INT1 and INT2 -treated wine according to PCA analysis. In addition, INT1 treatment enhanced antioxidant activity and resulted in minimal color loss. In conclusion, the INT1 enzyme extracts exhibit potential for wine fermentation applications, with preliminary performance in enhancing aroma quality, polyphenol profiles and antioxidant activity of red wine. The results provide a theoretical basis for revealing the mechanism of improving wine quality via Alternaria sp. MG1-based mixed fermentation, and also hold significance for the development of novel β-glucosidase-producing microbial resources. • Five β-glycosidase-encoding genes were identified and classified into three subclasses • Commercial medium increased protein yield and β-glycosidase activity in MG1 extracts • Most treatments significantly increased tannins and flavanols while minimizing color loss • INT1 treatment effectively enriched acetate esters and other key volatile compounds • The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.