Vitamin B-12 was produced by probiotic Lactobacillus plantarum in submerged fermentation (96 h) with successive anaerobic and aerobic phases of 48 h each to give 13 ng vitamin B-12/g dry biomass. Sodium cyanide-mediated cell lysis, followed by benzyl alcohol/chloroform/water extraction, improved the release of intracellular vitamin B-12 for analysis. The presence of the K+ adduct of cyanocobalamin (m/z of 1394) was established using electron spray ionization-mass spectra; growth of a mutant of Escherichia coli in the presence of cyanocobalamin ascertained its bioavailability.