The continuous two step conversion of 4-oxoisophorone(OIP) to 4-hydroxy-2,2,6-trimethylcyclohexanone(4-HTMCH) via dihydrooxoisophorone(DOIP) was carried out using two types of thermophilic growing cells, Thermomonospora curvata and Bacillus stearothermophilus, in sequential connected continuous stirred tank reactor(CSTR) and hollow fiber reactor system. For more than 80 hours operation, 46 % of OIP was converted to 4-HTMCH with productivity of 179 mg/h/l.