Out of 103 Egyptian local actinomycete isolates, Streptomyces SW1 was selected for vitamin 812 production. This isolate was completely identified as Streptomyces baamensis. The aim of the present study was to se'ect a cheap agriculturaJ or manufacturai by-product in the modified starch nitrate fermentation medium for higher vitamin 812 production. Results revealed that mo?asses at 15 g L1 , instead of starch in modified starch nitrate medium, proved to be the best by product for vitamin 812 production by the S. baamensis strain SWL Moreover, some environmental factors i.e. incubation period, initial pH value, temperature and shaking rate at different levels were tested for the optimization of fermentation process to yield the highest cyanocobalamin concentration. Results clearly showed that the optimal production of vitamin B12 was reached under submerged culture condition on the modified fermentation medium containing 15 g L1 molasses with initial pH value of 6 and a temperature of 28 oc after 4 days on a rotary shaker at the rate of 200 rpm, being 53.20 pg ml1.