The predominance, biodiversity and biotechnological properties of Kluyveromyces marxianus in the production of Pecorino di Farindola cheese

Pecorino di Farindola is a handicraft cheese made by farmers on small scale using raw ewes' milk and pig rennet. In this study, yeast consortia were evaluated during Pecorino di Farindola making and ripening. Molecular identification of 156 isolates was achieved by a combination of PCR-RFLP of the 5.8S ITS rRNA region and sequencing of the D1/D2 domain of the 26S rRNA gene. Kluyveromyces marxianus was the predominant species, while other species (Pichia kudriavzevii, Candida parapsilosis, Candida glaebosa and Candida zeylanoides) were present only during the early weeks of ripening. Moreover, the isolates were differentiated both by RAPD-PCR and a sequence alignment of D1/D2 26S rRNA gene, revealing different K. marxianus profiles and variants, and suggesting the role of local selective pressure as the origin of distinctive K. marxianus populations. The strains were characterized also on the basis of different dairy properties such as growth temperature, lactose, galactose, lactate and citrate assimilation at different NaCl concentrations, as well as lipolytic and caseinolytic activities. Moreover, 39 selected K. marxianus strains were inoculated in pasteurized whey to evaluate their growth kinetics, besides lactose, lactate and free amino acids metabolism. The growth kinetics distinguished different biotypes and different metabolic behavior were determined. The general picture of K. marxianus population from Pecorino di Farindola shows a high biodiversity at genetic and phenotypic levels that potentially offers many opportunities for new and advanced knowledge at species level, providing in the meantime a good basis to study the relationship between genetic variability and functional diversities.