Various cinnamate derivatives were tested as inducers for reduction of C-C double bonds in Acetobacterium woodii. The double bond and a phenyl ring were essential for induction, since crotonate and hydrocaffeate were ineffective as inducers whereas cinnamate derivatives were effective. Induction was improved by ring hydroxylation, except in the 2-position, since caffeate and 3- and 4-hydroxy cinnamate were the most effective inducers. The carboxylate group of cinnamate could be replaced by ester (methylcinnamate) or aldehyde (cinnamaldehyde), but not by alcohol (cinnamyl alcohol) or methyl (trans-beta-methylstyrene). Effective inducers were hydrogenated efficiently during growth, whereas ineffective inducers were not metabolised. Several inducers with intermediate effectiveness were hydrogenated in low yield with accompanying metabolism of other functional groups. Overall, caffeate (3,4-dihydroxycinnamate) was the best inducer. (c) 2006 Elsevier Inc. All rights reserved.