This research was conducted to study the effect of some nutrients on the growth and production of vitamin B12 by Lactobacillus genus L.rhamnosus, when their ability to produce vitamin B12 was tested under different conditions. The results indicate that a pH of 7 is optimal for vitamin B12 production by the bacteria L.rhamnosus and it was found that the optimum incubation temperature for the production of vitamin B12 ranged between 30 - 35 °C, with regard to the effect of the incubation period

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... the biological activity and productivity of vitamin B12. The results showed that 3 days was the best in the production of vitamin B12. The results also showed that adding the lowest concentration of cobalt chloride gave a high productivity of the vitamin compared to the highest added concentrations and that the best carbon source was sucrose among the three carbon sources that included glucose, fructose, and sucrose, and the results of the study showed that the best nitrogen source It is was peptone compared to yeast extract, which gave the highest production of the vitamin B12.