Characteristics of growth and EDTA degradation by chemostat culture of bacterial strain DSM 9103 were investigated. The effect of specific growth rate (mu) on mass cell yield (Y-x/s), specific rate of EDTA uptake (q(s)) and the rate of Mg-EDTA degradation by a cell suspension (q(s)(rest)) was studied. Based on the experimental data, kinetic constants of dependencies q(s)(S) and mu(S) were determined. The rates of substrate and energy expenditures for cell maintenance, m(s) and m(e), were 0.02 and 0.014 h(-1), respectively. High efficiency of DSM 9103 growth on EDTA in a chemostat was established; the maximum mass cell yield (Y-X/S(m)) and the maximum energy cell yield (eta(X/S)(m)) were as high as 35.3 and 50.5%, respectively. Results indicated that oxidation of side chains in the EDTA molecule by monooxygenase is coupled with energy utilization by the cells. Cells harvested from a chemostat (resting cells) retain the capability of EDTA degradation, although at a rate about four to five times lower than growing cells. (C) 2003 Elsevier Science Ltd. All rights reserved.