Yeasts and filamentous fungi associated with some dairy products in Egypt

Abstract

This work aimed to identify and evaluate the diversity of yeasts and filamentous fungi that contaminate some dairy products (fresh buffalo milk, plain yoghurt, butter and Kareisk cheese) in Assiut city, Egypt. The identification was based on phenotypic characteristics, and genotypically in case of yeasts. The pHs of all dairy products lie within the acidic range, but yoghurt registered the highest value. A total of 41genera and 89species+3varieties were recovered from all dairy products investigated on DRBC (26genera representing 59species+1variety), DG18 (32genera, 56species+2varieties) and MY50G (31genera, 64species+2varieties). From these, filamentous fungi were represented by 21genera and 59species+2varieties, and yeasts by 20genera and 30species+1variety. In all products except yoghurt, the xerophilic media (DG18and MY50G) supported more diversity of fungal species than the general medium (DRBC). Reversely, DRBC supported more propagules originated from all products than DG18and DRBC. On the other hand, the highest numbers of propagules were recovered from Kareish cheese and butter on MY50G, while the lowest numbers were recorded from yoghurt and raw milk on MY50G. Moreover, yeasts constituted the greatest part of propagules from the four products on the three isolation media except the raw milk on MY50G. From yeasts, Candida, Cyberlindnera, Debaryomyces, Galactomyces, Kazachstania, Kluyveromyces, Myerozyma, Pichia, Rhodotorula, Trichosporon; and from filamentous fungi, only Aspergillus, Cladosporium, Mucor and Penicillium were found contaminating all dairy products. Possible medical problems related to the presence of these fungi or to their metabolic products are discussed.