Succinic acid was produced efficiently from fumaric acid by a recombinant E. coli strain DH5 alpha/pGC1002 containing multicopy fumarate reductase genes. The effects of initial fumaric acid and glucose concentration on the production of succinic acid were investigated. Succinic acid reached 41 to over 60 g/L in 48.5 h starting with 50 to 64 g/L fumaric acid. Significant substrate inhibition was observed at initial fumaric acid concentration of 90 g/L. L-Malic acid became the major fermentation product under these conditions. Provision of glucose (5-30 g/L) to the fermentation medium stimulated the initial succinic acid production rate over two folds.