Screening for the production of extracellular hydrolytic enzymes by non-Saccharomyces wine yeasts
Aims: The objective of this study was to investigate what types of enzymes are being produced by non-Saccharomyces yeasts isolated from grapes in South Africa vineyards and clarified grape juice. These enzyme profiles could pave the way for attributing specific effects in wine to some of these enzymes produced by so-called wild yeasts associated with grape must. Methods and Results: In this study 245 yeast isolates, belonging to the genera Kloeckera, Candida, Debaryomyces, Rhodotorula, Pichia, Zygosaccharomyces, Hanseniaspora and Kluyveromyces were screened for the production of extracellular pectinases, proteases β-glucanases, lichenases, β-glucosidases, cellulases, xylanases, amylases and sulphite reductase activity. These yeasts, representing 21 species, were previously isolated from grapes and clarified grape juice. The production of all extracellular hydrolytic enzymes screened for was observed except β-glucosidase activity. The amount and range of enzymes produced varied with different isolates of the same species. Conclusion: This study clearly revealed the potential of non-Saccharomyces wine yeasts to produce a wide range of useful extracellular enzymes during the initial phase of wine fermentation. Significance and Impact of the Study: Enzymes produced by indigenous yeasts associated with grapes and juice might be harnessed to catalyse desired biotransformations during wine fermentation.