Characterization of Zygosaccharomyces lentus Yeast in Hungarian Botrytized Wines

Tokaj botrytized sweet wines are traditionally aged for several years in wood barrels or bottles. As they have significant residual sugar content, they are exposed to microbial contamination during ageing. Osmotolerant wine-spoilage yeasts are most commonly found in the Tokaj wine-growing region in the species Starmerella spp. and Zygosaccharomyces spp. For the first time, Z. lentus yeasts were isolated from post-fermented botrytized wines. Our physiological studies confirmed that these yeast strains are osmotolerant, with high sulphur tolerance and 8% v/v alcohol tolerance, and that they grow well at cellar temperature in acidic conditions. Low β-glucosidase and sulphite reductase activities were observed, whereas protease, cellulase, and α-arabinofuranosidase extracellular enzyme activities were not detected. Molecular biology analyses carried out by RFLP analysis of mtDNA revealed no remarkable differences between strains, while microsatellite-primed-PCR fingerprinting of the (GTG)₅ microsatellite and examination of chromosomal pattern revealed considerable diversity. The fermentative vigour of the tested Z. lentus strains was found to be significantly lower compared to the control Saccharomyces cerevisiae (Lalvin EC1118). It can be concluded that Z. lentus is a potential spoilage yeast in oenology which may be responsible for the initiation of secondary fermentation of wines during ageing.