A fed-batch culture was applied for the production of colominic acid from Escherichia coli. It was found that the copper ion, which is a trace element in medium and an essential element in N-acetylneuraminic acid synthase, affected the colominic acid production and the highest production was obtained using 1.6 mg/l CuCl2. Ammonia formed from nitrogen source utilization greatly affected colominic acid production and only slightly affected the cell growth. A flow injection analysis (FIA) system was fabricated and applied to monitor and control the ammonia concentration in the culture broth. It was found that a concentration of 0.3 g/l of ammonia was optimal for colominic acid production where 1.9 g/l was obtained.