Characterization of Stress Tolerance and Probiotic Traits of Streptococcus salivarius Strains Isolated from Wildflower Honey

Aims Honey represents a distinct microbial habitat, imposing physicochemical stresses on its resident microbiota while also serving as a potential source of beneficial microorganisms. This study aimed to isolate lactic acid bacteria (LAB) from Korean wildflower honey and characterize their gastrointestinal (GI) and physiological stress tolerance, adhesion-related properties, functional characteristics, and safety to evaluate their potential as probiotic candidates. Methods and Results Two Streptococcus salivarius strains, DOW-5A and DOW-10, were isolated from Korean wildflower honey and identified by phenotypic and molecular analyses. Both strains survived in sequential exposure to simulated GI conditions and showed tolerance to physiological stresses. DOW-5A maintained higher viability during the simulated gastric phase, whereas DOW-10 showed an initial decrease in viable counts followed by an increase during the simulated intestinal phase. The two strains also exhibited various probiotic characteristics, including mucin adhesion and antioxidant activity. Atypical, crystalline colony morphologies associated with EPS production were observed when sucrose was supplied as a carbon source. Both strains formed biofilms, while DOW-5A showed a marked increase in biofilm formation upon sucrose supplementation. Neither strain showed gelatinase or hemolytic activity or significant cytotoxicity toward Caco-2 cells. Impact Statement In this study, we isolated two honey-derived S. salivarius strains with high probiotic potential. Our findings highlight wildflower honey as a potential reservoir of LAB with traits relevant to survival under GI and physiological stresses, as well as various probiotic traits.