The gene encoding an enoate reductase was cloned from the genomic DNA of Bacillus cereus WZY004 and over-expressed as a soluble protein in Escherichia coli BL21 (DE3). The recombinant enzyme was purified by Ni-NTA affinity chromatography and subsequently characterized. The SDS-PAGE analysis of the purified enzyme revealed a single band corresponding to the molecular weight of around 38.2 kD. The enzyme exhibited the maximum activity at pH 7.0 and
temperature 60 °C. The values of Km and Vmax for ketoisophorone were 1.83 mmol/L and 1.13 U/mg, respectively. In addition, the purified enzyme showed higher activity when citral, 2-methyl-2-pentenal or trans-2-decenal was used as substrate.