Isolation, identification and in vitro probiotic characterisation of yeast strains found in fermented turnip juice

The probiotic characteristics of yeasts isolated from fermented turnip juices collected from different cities of Türkiye were investigated. Most of the isolates were identified as Pichia kudriavzevii (45%), P. fermentans (20%), P. occidentalis (15%) and P. manshurica (12.5%). Regarding their probiotic properties, all strains showed viability at pH 3 and 4, and 24 strains belonging to P. occidentalis, P. kudriavzevii and Saccharomyces cerevisiae were tolerant to pH 2, 3 and 4. All strains showed tolerance to bile salts (55.92-139.17%), phenol (43.88–130.46%), pepsin (66.32–111.70%) and pancreatin (86.19–116.10%). The proteolytic activity of all but 4 strains ranged from 0.001 to 0.077 mg tyrosine/mL, and they did not exhibit β-galactosidase activity. All strains were viable in the presence of 1.5% NaCl, and approximately 60% were viable in the presence of 10% NaCl. Their cell surface hydrophobicity towards xylene varied between 1.53% and 56.22%. P. kudriavzevii LM4 showed the highest hydrophobicity. The auto-aggregation of the strains varied from 23.01 to 63.91%, while the co-aggregation ability with Salmonella Typhimurium varied from 1.64 to 51.69%, with significant differences between the strains. Thus, the yeast strains from fermented turnip juice exhibit probiotic potential and can be used to develop new probiotic food products or supplements.

Graphical Abstract