Novel Skin- and Oral-Derived Probiotic Candidates: Functional Evaluation and Application Perspectives

The skin and oral environment represent complex microbial ecosystems that host diverse bacterial communities with potential health-promoting properties beyond the gastrointestinal tract (GIT). In this study, four bacterial and three yeast isolates were obtained from saliva (S1, S3, S5, and S6) and human skin (A1, A2, and A3) and subjected to identification and functional characterization. Phenotypic identification by API and MALDI-TOF mass spectrometry identified bacterial isolates as Limosilactobacillus sp. (S1) and Lacticaseibacillus rhamnosus (S3, S5, and S6), while the yeasts were identified as Saccharomyces cerevisiae (A1, A2, and A3). The isolates were evaluated for their functional properties, including antimicrobial activity, autoaggregation, antioxidative potential, resistance to freeze-drying, survival in simulated saliva and GIT conditions, adhesion to Caco-2 and HaCaT cell lines, and biofilm-forming ability. Lcb. rhamnosus S3 demonstrated the highest probiotic potential, characterized by strong inhibition of S. aureus, high autoaggregation capacity, substantial survival following freeze-drying, and good tolerance to simulated saliva and GIT conditions. Limosilactobacillus sp. (S1) demonstrated the strongest antimicrobial activity against C. acnes and the highest adhesion capacity to HaCaT cells, indicating its suitability for topical dermatological applications. Although S. cerevisiae isolates did not exhibit antimicrobial activity, they showed strong autoaggregation and notable antioxidant capacity. However, their low resistance to freeze-drying limits their applicability in probiotic formulation development.