Characterization of extracellular vitamin B12 producing Lactobacillus plantarum strains and assessment of the probiotic potentials

•Two L. plantarum strains with high extracellular vitamin B12 yields were isolated.•The extracellular B12 from L. plantarum LZ95 were identified as Ado-Cbl and Me-Cbl.•LZ95 showed good tolerance to environmental stresses, low pH and bile salts.•LZ95 exhibited great adhesion to Caco-2 cells.•LZ95 might be a potential candidate for in situ B12 fortification in food industry.

We investigated extracellular vitamin B12-producing Lactobacillus strains and their characteristics in tolerance to environmental stresses, gastric acid and bile salts. Two isolates, Lactobacillus plantarum LZ95 and CY2, showed high extracellular B12 production, 98 ± 15 μg/L and 60 ± 9 μg/L respectively. Extracellular B12 from LZ95 were identified as adenosylcobalamin and methylcobalamin using a combination of solid phase extraction and reverse-phase HPLC, while that from CY2 was adenosylcobalamin. Both strains grew under environmental stresses, and LZ95 exhibited better tolerance to low temperature and high ethanol concentration. LZ95 also showed good viability when exposed to gastric acid (pH 2.0 and 3.0) and bile salts (0.3%) as well as good adhesion to Caco-2 cells. The viability of CY2 was significantly reduced under low pH and exposure to bile salt. Together, extracellular B12 producer LZ95 with good probiotic properties might be a candidate for in situ B12 fortification in the food industry.