Abstract: Erythromycin biosynthesis is a highly complicated process,which involves both primary metabolism and secondary metabolism.The activities of the key enzymes related to glucose metabolism such as glucose kinase,glucose-6-phosphate dehydrogenase,phosphofrutokinase and isocitrate dehydrogenase in Saccharopolyspora erythraea,and the activities of the enzymes involved in secondary metabolism,such as methylmalonyl-coenzyme A mutase,and methylmalonyl-coenzyme A transcaboxylase,were determined.Some organic acids in fermentation broth were also analyzed.Results show that Co~(2 ) increases erythromycin biosynthesis.It maybe owe to improvement of the specific activities of methylmalonyl-coenzyme A mutase and methylmalonyl-coenzyme A transcaboxylase by Co~(2 ).Meanwhile,it also increases the flux of glucose metabolism pathway.