Internal transcribed spacer as a target to assess yeast biodiversity in Italian Taleggio PDO cheese

Three batches of soft smear-ripened Taleggio PDO cheese were made in Northern Italy during the summertime 2010. A total of 129 isolates cultured from cheese surface were examined by using PCR-based methods and sequencing of both the ITS1 region and D1 and D2 domains of the 26S rRNA gene. Sequence analysis of isolates brought to the identification of 6 species: Debaryomyces hansenii, Kluyveromyces lactis, Kluyveromyces marxianus, Yarrowia lipolytica, Pichia guilliermondii, and Torulaspora delbrueckii. Analysis of DNA directly extracted from 45 cheese surfaces permitted to detect 2 additional species Candida sake and Candida etchellsii. D. hansenii was predominant and widespread whereas the other yeast species were detected less frequently. To determine the relationships between yeast community and the environment, 39 isolates from wooden boxes used for dry salting of cheese were analyzed as well. Sequencing of ITS1 region allowed to identify D. hansenii, T. delbrueckii, and K. lactis. ITS1 multiple sequence alignments of D. hansenii detected in wooden boxes showed an in-del polymorphism at position 169. ITS1 secondary structures of yeasts were modeled to explore new applications of this region for molecular identification purposes.

This study used molecular analysis to identify adventitious yeast population present in the surface of Taleggio smear-ripened cheese. D. hansenii was found predominant in pasteurized milk, in dry salting equipment, and in all cheese samples until the end of ripening.