Comparison of specific enzyme activities in wild-type Propionibacterium jensenii ATCC 4868 and transformants overexpressing the gldA, mdh, and fumC genes. In fed-batch cultures of wild-type P. jensenii ATCC 4868 and transformants, samples were obtained after 48 h to analyze GDH, MDH, and FUM activities. Black columns, FUM activity; red columns, GDH activity; blue columns, MDH activity.