Safety aspects and in vitro probiotic assessment of Kluyveromyces marxianus strains from neonatal faeces.

The isolation and identification of probiotic yeasts is increasing rapidly. In this context, the present study aimed to isolate and identify yeast strains from neonatal faeces in Erzurum province, Türkiye and to determine their probiotic characteristics. A total of 12 yeast strains were isolated and genotypic characterization revealed the presence of seven different species, including Kluyveromyces marxianus, Candida spp. Clavispora lusitaniae, Geotrichum candidum, Trichophyton rubrum, Pichia cactophila, and Meyerozyma guilliermondii. The non-pathogenic and potentially probiotic characteristics of the K. marxianus M2, M9, and M10 strains were further investigated. Although yeast has been isolated from neonatal faeces before, K. marxianus was isolated for the first time in this study. The results revealed that the K. marxianus strains exhibited high resistance to simulated gastric juice and bile salts. The auto-aggregation percentages of the strains ranged from 92.55 to 94.78% after 4 h, while the co-aggregation percentages with pathogens ranged from 19.70 to 53.09%. The K. marxianus M2 strain exhibited the highest degree of hydrophobicity (74.97%), and none of the strains demonstrated DN-ase or haemolytic activity. Furthermore, M2 and M9 strains displayed bile salt hydrolase activity. In conclusion, based on in vitro probiotic test results, K. marxianus strains were selected as probiotic yeast candidates for further studies, especially in patients under antibiotic therapy.