Identification of fungi from dairy products by means of 18S rRNA analysis

The role of fungi as cause of spoilage of dairy products, such as cheese and yoghurt, has been clearly demonstrated. Despite of this, there is still a lack in rapid methods for the identification of food-associated fungi. In the course of the present work, molecular taxonomical techniques were developed and used to identify yeasts involved in the spoilage of yoghurt and moulds responsible for spoilage of vacuum-packaged hard cheese. Three methods for DNA extraction and purification were evaluated and the fungus-specific primers TR1 and TR2 were used to amplify a 581-bp fragment within the gene, coding for the small ribosomal subunit (18S rRNA) of fungi. The 18S rRNA sequence analysis of fungi isolated from yoghurt and packaged cheese allowed to identify yeast belonging to Zygosaccharomyces microellipsoides and moulds belonging to Penicillium chrysogenum and Cladosporium cladosporoides.