Decoding the microbiota of borş: multifunctional potential of a traditional Romanian beverage fermentation

Romanian borş, a traditional fermented wheat bran beverage, is produced through spontaneous fermentation and represents a complex microbial ecosystem. Despite its cultural importance and presumed health benefits, its microbial ecology and functional potential remain poorly characterized. The present study aimed to elucidate the microbial community structure of borş and link it to functional traits relevant to fermentation performance and food functionality by integrating culture-independent sequencing with culture-dependent isolation and functional characterization. A total of 32 borş samples (12 commercial and 20 homemade) were analyzed. Amplicon-based sequencing revealed a microbiome dominated by lactic acid bacteria (LAB), with lactobacilli accounting for the majority of the bacterial communities and Lactobacillus amylolyticus being identified as the most prevalent and abundant species. The yeast communities were mainly composed of fermentative taxa, including Pichia kudriavzevii and Kluyveromyces marxianus . Lactobacillus amylolyticus and P. kudriavzevii were also the most frequently isolated species among bacteria and yeasts, respectively. These results highlighted a strong adaptation of the microbial isolates to starch-rich cereal substrates and underscored the central role of these microorganisms in wheat bran fermentation for borş production. Whereas the sequencing-based analyses showed no significant differences in overall diversity between the commercial and homemade borş samples, the cultivation-based results indicated a higher bacterial richness in the commercial products. Notably, the culture-dependent method captured substantially fewer taxa, highlighting the complementary nature of the two approaches. Of a total of 101 bacterial strains (88 LAB and 13 acetic acid bacteria) isolated, many exhibited rapid growth and strong acidification capacity, reaching pH values below 4.5 within 12 h. A functional screening revealed that 21 % of these strains displayed α-amylase activity, 65 % phytase activity, and 50 % β-glucosidase activity, highlighting their capacity to metabolize cereal substrates and enhance the nutrient availability of borş. All strains showed antibacterial activity against at least one indicator bacterium tested, with a universal inhibition of Listeria monocytogenes . Overall, Romanian borş harbored a lactic acid bacteria-dominated core microbiome with a significant functional diversity. These findings underscored its potential as a rich source of functional and technologically important strains for application in starter and protective culture development.