Production of Vitamin B12 from microbial sources has many advantages over conventional chemical synthesis. In the present investigation, an attempt was made to isolate and characterize the environment friendly symbiotic Rhizobium species from its natural host, Sesbania sesban (L) root nodules, as source of adenosylcobalamin producer. A total of 75 isolates of Rhizobium were obtained and characterized by morphological, biochemical, and molecular methods. All the isolates obtained, produced the compound of interest in the range of 0.57 ppm. Two isolates, namely, AMB and PMT4 showed higher production of Adenosylcobalamin than the others. These isolates, on optimization showed increased production (28±0.26 ppm and 19±0.26 ppm). Beet Molasses, Cobalt Nitrate, and 5,6 DMB were found to be essential components for adenosylcobalamin production. Further, although betaine and Choline Chloride were revealed to affect the cell growth, they could elicit Adenosylcobalamin production. Thus, Rhizobium species has dual advantage as Vitamin B12 producer and as nitrogen fixing environment friendly organism. Further studies are warranted for genetic improvement to enhance Vitamin B12 production without affecting its nitrogen fixing ability.
Key words: Rhizobium sp.; Sesbania sesban; adenosylcobalamin; media optimization, submerged fermentation.
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