An application of PCR-DGGE analysis to profile the yeast populations in raw milk.

Four different zones from the Friuli Venezia Giulia region, North East of Italy, were sampled for the study of the yeast bio- diversity in raw milk. Samples were analysed by traditional methods to isolate different yeast strains that were subjected to identification by sequencing the D1–D2 domains of the 26S rRNA gene. Twelve different species of yeast were identified, six of them belonging to the genera Candida and two to the genera Kluyveromyces. The identified strains were then used for the optimization of a method based on polymerase chain reaction and denaturing gradient gel electrophoresis that was used for a direct monitoring of the populations in the samples. Applying the method to the DNA extracted directly from the raw milk samples, new bands appeared in the gel underlining a different bio-diversity in respect to the traditional method. The approach described is a powerful and reliable tool to monitor directly yeast ecology in milk and milk products without the need of traditional isolation and it could be used to follow specific populations to prevent spoilage or to control contamination.