Molecular and phenotypic characterization of Pichia fermentans strains found among Boza yeasts

Fifty-one yeasts were randomly isolated from four different preparations of Boza, a Turkish cereal-based beverage in order to throw light upon their biotechnological potential. Sequence analysis of 26S rDNA D1/D2 domain revealed that the isolated yeasts belonged to Candida, Clavispora, Cryptococcus, Cystofilobasidium, Geotrichum, Coniochaeta, Pichia, Rhodotorula, Saccharomyces, Torulaspora and Trichosporon genera. Interestingly, Pichia fermentans resulted the dominant species with 21 isolates; a high polymorphism among these yeasts resulted by RAPD-PCR analysis which allowed to distinguish 15 strains that were characterized for their biochemical and technological features. In addition, all P. fermentans strains did not assimilate D-maltose and D-sucrose and expressed a very low invertase activity, suggesting their possible coexistence with maltose- and sucrose-fermenting lactic acid bacteria in Boza microbial ecosystem. Three yeasts produced a high amount of the rose-like fragrance 2-phenylethanol that might be involved in flavor development of this traditional beverage. Moreover, these yeasts also displayed an antagonistic activity against Trichosporon cutaneum, a pathogen occurring in Boza. These selected yeasts are at disposal of Boza manufacturers who could apply them, in combination with LAB, for producing a high quality beverage in accordance with the Turkish quality standards. (C) 2012 Elsevier Ltd. All rights reserved.