A chemostat was operated to characterize degradation of bisphenol A by Sphingomonas paucimobilis FJ-4. The chemostat at 30 degrees C was fed with a medium containing 150 mg L-1 of BPA as the sole carbon and energy source. At the short cell retention time of 8 h, the bacterial cells were washed out from the chemostat. At long cell retention times of 12,16, 24, and 48 h, steady -states of the bacterial growth on BPA degradation were achieved after a lag time of 16-57 h. A mathematical model was applied to evaluate the BPA degradation ability of strain FJ-4. The maximum specific degradation rate, the half saturation constant, the cell yield, and the specific decay rate were estimated respectively as 0.46 mg-BPA (mg-VSS h)(-1), 13.1 mg L-1, 039 mg-VSS mg-BPA-1, and 0.0014 h(-1). (C) 2016, The Society for Biotechnology, Japan. All rights reserved.