Tris(1,3-dichloro-2-propyl) phosphate (TDCPP), a flame retardant, is regarded as a potentially toxic and persistent environmental contaminant. We previously isolated a TDCPP-degrading bacterium, Sphingobium sp. strain TCM1, which, however, produced a toxic metabolite: 1,3-dichloro-2-propanol (1,3-DCP). This study was undertaken to develop a technique for complete TDCPP detoxification using strain TCM1 with a 1,3-DCP-degrading bacterium, Arthrobacter sp. strain PY1. For efficient detoxification, we designed a resting cell system and examined the effect of freezing and lyophilization treatments for preparation of their resting cells. Results show that treatments had no marked adverse effect on their activities. The TDCPP dephosphorylation by TCM1 resting cells was optimal at 30 degrees C and pH 8.5. Also, 1,3-DCP dehalogenation by strain PY1 resting cells was optimal at 35 degrees C and pH 9.5. Under those respective conditions, the activities were 2.48 mu mol h(-1).OD660-1 for TDCPP and 0.95 mu mol h(-1).OD660-1 for 1,3-DCP. Based on these results, we set the reaction temperature to 30 degrees C and pH to 9.0. Then we examined the detoxification of 50 mu M TDCPP using mixed resting cells at a final OD660 of 0.05 for strain TCM1 and 0.2 for strain PY1. In these conditions, TDCPP was eliminated after 1 h, but some of the resulting 1,3-DCP remained at a constant level. The increase in strain PY1 cells to a final OD660 of 4.0 decreased the TDCPP dephosphorylation rate of strain TCM1 cells but achieved complete detoxification of TDCPP during 12 h of reaction. (C) 2011, The Society for Biotechnology, Japan. All rights reserved.