Phenotypic and Genotypic Identification and Characterisation of Yeasts from Austrian Milk Products

A polyphasic approach including phenotypic (morphological, biochemical and physiological characterisation) and genotypic (RAPD-PCR, sequencing of genes coding for 26S and 18S rRNA) methods was used for the identification of yeasts isolated from different milk products. There were 514 yeast isolates in all, 461 ascomycetous and 53 basidiomycetous strains. By means of the applied polyphasic approach it was possible to identify 92% strains altogether. The following species were defined: Candida catenulata, C. incospicua, C. intermedia, C. parapsilosis, C. pararugosa, C. pseudoglaebosa, C. saitoana, C. sake, C. sojae, C. zeylanoides, Clavispora lusitaniae, Debaryomyces fabryi, D. hansenii, Geotrichum candidum, Issatchenkia orientalis, Kluyveromyces lactis, K. marxianus, Pichia fermentans, P. guilliermondii, Saccharomyces cerevisiae, S. unisporus, Torulaspora delbrueckii, Yarrowia lipolytica, Cryptococcus curvatus, Rhodotorula mucilaginosa, Trichosporon cutaneum and T. ovoides. The largest part of microflora was represented by D. hansenii and K. marxianus. They were followed by G. candidum, C. zeylanoides and Y. lipolytica. The majority of the yeasts were isolated from fresh and sour curd cheese. The phylogenetic studies on the basis of 26S and 18S rDNA sequences as well as the RAPD-analysis showed that the new species of the genera Yarrowia, Rhodosporidium, Cryptococcus and Trichosporon could be characterised. The results described in this work clearly show that molecular identification is an excellent alternative approach to the time consuming physiological tests.