Detection of non-Saccharomyces yeast strains in alcoholic fermentations by direct PCR and/or plating methods

Abstract

Since the population of indigenous non-Saccharomyces yeasts is displaced from an alcoholic fermentation within a few hours, the use of a selective enrichment broth would be a valid approach for their detection. To accomplish this, yeast carbon base (YCB)–lysine broth without or with different concentrations of cycloheximide was tested. Lysine is an amino acid that cannot serve as the only nitrogen source for Saccharomyces spp., which is in contrast to non-Saccharomyces yeast, while cycloheximide is an antibiotic that is more or less effective against Saccharomyces spp. strains. Metagenomics, the study of genetic material from mixed microbial community as a grape must fermentation has the potential for operating in a culture-independent environment. Direct identification by PCR (dPCR) without previous isolation and a classical approach to analyse the yeast population in a wine inoculated with a mixed population of Saccharomyces cerevisiae and non-Saccharomyces yeasts were compared. Results showed that pre-incubation on YCB–lysine and dPCR combined with classic approaches based on the use of solid media is a suitable strategy for detecting yeast species involved in vinifications.