Acetobacterium woodii was grown on fructose, methanol, 3,4, 5-trimethoxycinnamate, or 3-(3,4,5-trimethoxyphenyl)-propanonte in the presence or absence of caffeate. The cells were harvested and tested for their ability to hydrogenate C=C bonds using caffeate as a model substrate. Except for cells grown on methanol, the growth substrate was a poor, election donor for the biotransformation. 3-(3,4,5-Trimethoxyphenyl)-propanoate was the best dorter for fructose-grown cells while fructose was the best donor for cells grown on methoxy-substituted aromatics. Caffeate reductase activity was inducible by caffeate or trimethoxycinnamate. The highest rates of caffeate reduction were obtained using cells which had been grown on 3,4,5-trimethoxycinnamate plus caffeate and by providing fructose as the electron donor.