Molecular identification and phylogenetic analysis of yeast strains isolated from dairy products in Isfahan, Iran

Yeasts play a dual role in dairy processing, serving as beneficial fermentative agents that enhance product quality through flavor, texture, and probiotic properties, while also posing spoilage risks if uncontrolled. This study aimed to characterize yeast isolates from industrial and traditional dairy products in Isfahan using PCR-sequencing and phylogenetic analysis.

A total of 155 dairy samples (fresh/stored, traditional/industrial) were collected. Yeasts were cultured and identified via PCR amplification and sequencing of the ITS1-5.8S rDNA-ITS2 region.

Analysis of ITS sequence data identified 28 yeast strains representing eleven species across seven genera, including Saccharomyces cerevisiae (n=8) Kluyveromyces marxianus (n=6), Pichia kudriavzevii (n=4), Candida orthopsilosis (n=2), Pichia membranifaciens (n=2), Pichia cactophila (n=1), Pichia fermentans (n=1), Galactomyces candidum (n=1), Torulaspora delbrueckii (n=1), Debaryomyces hansenii (n=1), and Kluyveromyces lactis (n=1). Phylogenetic analysis grouped isolates into two clusters. Industrial cheese and both industrial/traditional yogurts showed the highest yeast diversity and counts. Notably, C. orthopsilosis was found only in industrial milk and cheese, suggesting potential processing-related contamination.

This study highlights the diversity of yeast microbiota in dairy products and underscores the efficacy of ITS sequencing for accurate yeast identification in the dairy industry, aiding quality control and spoilage prevention.