Phenotypic and genotypic diversity of yeasts isolated from water-buffalo Mozzarella cheese

Water-buffalo Mozzarella (WBM) cheese is one of the several 'pasta filata' or stretched curd cheeses that originated in southern Italy, traditionally manufactured from raw milk employing natural whey starter cultures. Lactose - and galactose-fermenting yeasts isolated from WBM were studied to evaluat e their role in the ripening of this cheese. The kinetic parameters of the growth of the yeasts as well as their principal metabolic end-products show ed a great variability depending on the species. Moreover, the genetic polymorphism of the yeasts was studied for their diff erentiation at species level by means of the polymerase chain reaction (PCR ) fingerprinting and mitochondrial DNA (mtDNA) restriction analysis. While the differentiation based on metabolic traits was not able to discriminate Kluyveromyces marxianus, Candida kefyr and C. sphaerica, the PCR analysis w ith primers M13 and RF2 resulted in a reliable and rapid method for differe ntiating at species level Saccharomyces cerevisiae, K. marxianus, K. lactis and their anamorphic species. Furthermore, mtDNA analysis proved to be mor e discriminating at strain level.