Assessing lactococcal and enterococcal strains derived from traditionally fermented kefir and nabeez for their prospects as probiotics

Consumers' healthy lifestyle practices have heightened the appeal of minimally processed foods, especially the fermented kind. Kefir and nabeez with numerous benefits are world-famous beverages. This study aimed to explore the enterococcal and lactococcal probiotic strains associated with these beverages. Artisanal recipes were used to make kefir and nabeez, and bacteria were isolated using classical culturing techniques. The isolates were screened based on antimicrobial potential, safety and probiotic attributes. The bacterial isolates obtained from three fermented beverages, milk kefir, water kefir and nabeez, were assessed for safety concerns, and those deemed safe were tested for antagonistic potential. Strains of <i>Enterococcus durans</i> (NPL1395_MK, NPL1396_MK and NPL1480_MK), <i>Enterococcus faecium</i> (NPL1390_MK, NPL1420_WK and NPL1427_Nb) and <i>Lactococcus lactis</i> (NPL1426_Nb, NPL1428_Nb and NPL1436_Nb) demonstrated interesting antimicrobial characteristics against food-borne pathogens. Strains from milk kefir and nabeez could tolerate strong acidic and bile stress. All strains were susceptible to lysozyme and phenol at the concentrations tested but demonstrated significant antioxidant potentials, exopolysaccharide production and bile salt hydrolase activities. Cholesterol assimilation was most significant in milk kefir and nabeez strains, which also had good adherence and biofilm formation. Statistical analysis of performance data using the principal component analysis identified <i>L. lactis</i> strain NPL1428_Nb as the best. It exhibited good potential to persist in the human gut based on its ability to tolerate <i>in vitro</i> mixtures simulating the gastrointestinal tract digestive fluids, using the static digestion model. Therefore, strain NPL1428_Nb of traditional fermented beverage provenance has good prospects for use in probiotic product development.