Investigating tryptophan-producing probiotic lactic acid bacteria from Lithuanian fermented foods: functional characterization, safety evaluation, and genomic analysis

This study aimed to isolate and characterize lactic acid bacteria (LAB) from traditional Lithuanian fermented foods and evaluate their probiotic potential, safety, and ability to produce tryptophan. Around 20 LAB isolates were screened for gastrointestinal tolerance, antimicrobial activity, aggregation, and adhesion to intestinal cells. Only 5 strains were identified and further analyzed using whole-genome sequencing and in vitro assays. Among them, Leuconostoc mesenteroides KA15 showed enhanced survival under simulated gastrointestinal conditions and produced 10.48 μM tryptophan in the presence of fructooligosaccharides. Genomic analysis confirmed the absence of virulence and transferable antibiotic resistance genes in selected strains. While some isolates exhibited antimicrobial activity and adhesion capacity, phenotypic antibiotic resistance excluded certain candidates from probiotic consideration. Overall, KA15 demonstrated the most promising combination of functional and safety characteristics. These findings highlight traditional fermented foods as a source of potentially beneficial LAB supporting further studies to evaluate their physiological effects in host systems.