[Biosynthesis, fermentation and application of vitamin B12--a review].

Vitamin B12 is an important nutrient widely used in feed, food and medicine field. China is the primary producing area and the VB12 production is 27 t in 2007, 77% of total production in the world. VB12 is the most complex small molecule difficult to chemosynthesize. It ismanufactured by bacteria and archaea via two alternative routes, aerobic or anaerobic pathway. The main strains used in industry fermentation are Propionibacterium freudenrechii and Pseudomonas denitrificans. The basic characteristics, biosynthesis and fermentation of vitamin B12 are reviewed. The vitamin B12 application and market are also summarized.