中文摘要：

对于工业化发酵而言，选择一种适宜的发酵原料对提高微生物发酵产量及降低发酵成本显得尤为重要。该文首先在合成培养基中考察了氨基酸对脱氮假单胞杆菌合成维生素B12的影响，结果表明谷氨酸等氨基酸对菌体生长和维生素B12合成具有较大的促进作用。甜菜糖蜜作为制糖工业的副产物，其成本相对低廉，但营养组分检测显示，甜菜糖蜜含有丰富的碳源和有机氮类物质，其中有机氮类又以谷氨酸居多，而且还含有一定量的合成维生素B12所必需的甲基供体甜菜碱。基于此，最终确立了以甜菜糖蜜作为维生素B12发酵的主要原料。在该原料下，脱氮假单胞杆菌摇瓶发酵结束时（168h）的菌体量（光密度）和维生素B12产量分别达到37．3mg／L和108．37mg／L。

英文摘要：

： During industrial fermentation, an appropriate medium has an important role in increasing productivity and decreasmg cost. The effects of amino acids on vitamin B12 biosynthesis by Pseudomonas deni~Bcans were investigated through chemically defined medium, and the results showed that glutamate had a positive effect on cell growth and vitamin Bl2 production. Beet molasses is a by-product of sugar industry, and its cost is comparatively low. But the nutrient component analysis showed that beet molasses had abundant carbon and organic nitrogen. For organic nitrogen contained in beet molasses, the content of glutamate was the highest. Furthermore, there was a high concentration ofbetaine in beet molasses, which was the necessary methyl-group donor for vitamin B12 biosynthesis. Based on this fact, beet molasses was chosen as the main medium component for vitamin B12 fermentation. In this case, the final biomass （optical density） and vitamin B12 yieldreached 37.3mg/L and 108.37mg/L, respectively.