Vitamin B12 (cobalamin) is crucial for human nutrition due to pernicious anemia, a rare condition causing malabsorption. It is synthesized by microorganisms like bacteria and archaea using aerobic and anaerobic biosynthetic pathways. The biosynthesis of the corrin ring involves aerobic and anaerobic pathways. Aerobic pathways involve oxygen molecules and cobalt chelationChelation steps, while anaerobic pathways insert cobalt earlier. Lower ligand synthesis has two routes: aerobic and anaerobic, catalyzed by BluB. Industrial production relies on high-productivity strains like Propionibacterium freudenreichii and P. denitrificans, with advances in bioprocess optimization and new strains emerging. The process of biosynthesis and quantification of vitamin B12 involves selecting substrates for microbial strain collection, fermentationFermentation of microbes to produce B12, preparation of suspensions, cultures, or inoculums, and quantification using HPLC. Various methods are employed, including HPLC, HPLC-MS, HPLC-DAD, UHLC, or MS, to measure the production of B12 from a wide range of microbes.