Isolation and Molecular Identification of Potential Probiotic Yeasts from the gastrointestinal tract of Beluga Fish

The colonized microorganisms in the fish gastrointestinal (GI) tract have recently received particular attention as a probiotic. Therefore, we aimed to identify potential probiotic yeasts from the GI tract of the beluga (Huso huso). The fish were randomly caught from beluga-breeding ponds. The isolated yeast strains were investigated for some properties of probiotic potentials, including tolerance to acidity and bile salt (Oxgall). Yeast strains with probiotic potentials were identified to species level using polymerase chain reaction and sequencing the internal transcribed spacer regions of rDNA. Seventeen different yeast strains were isolated from the beluga's GI tract based on macroscopic and microscopic characteristics. Nine yeasts (52.9%) could tolerate acid (pH = 2) for up to 3 h. Among acid-resistant yeasts, four yeasts could tolerate bile salts for up to 8 h. By comparing the obtained sequences with reference sequences in GenBank, all strains were identified as Candida parapsilosis. Sequence data of each strain were assigned in GenBank under the accession numbers. Identifying the fungal microbiota of healthy fish and determining their probiotic prospects can help us use them in aquaculture. Further extensive studies are recommended to identify fungal-biota with probiotic potential in more fish species.