Isolation of a novel Pseudomonas species SP2 producing vitamin B12 under aerobic condition

Vitamin B12 is a complex biomolecule that acts as a cofactor for a variety of enzymes in microbial metabolism. Pseudomonas denitrificans is exclusively used as an industrial strain for the production of vitamin B12 under aerobic conditions. However, only a few strains of Pseudomonas have been reported to possess the capability of producing this vitamin and they are strongly patent-protected. To improve the applicability of the vitamin B12-producing microorganisms, a new isolate was obtained from municipal waste samples and characterized for its biological properties. The new isolate, designated as SP2, was identified to be a Pseudomonas species based on the sequence homology of its 16S rDNA. Pseudomonas species SP2 had essential genes for vitamin B12 synthesis such as cobB and cobQ and produced a similar amount of vitamin B12 (10.6 ' 0.05 'g/mL) as P. denitrificans ATCC 13867 in 24 h flask culture. SP2 grew well under aerobic condition with the maximum specific growth rate (' max ) of 0.91 ' 0.03/h, but showed a poor growth under micro-aerobic conditions. SP2 was resistant to antibiotics like streptomycin, carbenicillin, ampicillin, cefpodoxime, colistin, nalidixic acid and sparfloxacin. The ability of SP2 to grow faster and produce vitamin B12 under aerobic conditions makes it a promising host for the production of some biochemicals requiring a coenzyme B12-dependent enzyme, such as glycerol dehydratase.