A biosensor approach was applied to study the degradation of ethylenediaminetetraacetate (EDTA) and metal-EDTA complexes with Mg2+, Mn2+, Ba2+, and Ca2+ by bacterial cells of strain DSM 9103 immobilised by sorption on Whatman GF/A chromatographic paper. Kinetic characteristics of EDTA degradation: maximum rate of oxygen consumption (V-max), saturation constant (K-s), and inhibitory constant (K-i) were determined from the measured values of oxygen consumption rate at different substrate concentrations. Values of V-max for all the substrates studied were similar whereas the values of K-s and K-i differed considerably. Uncomplexed EDTA and Ca-EDTA had the highest affinity to the EDTA-degrading system; Mn-EDTA showed the highest inhibitory effect. Results obtained offer considerable scope for the development of microbial biosensors sensitive to extremely low concentrations (5-100 muM) of EDTA. (C) 2002 Elsevier Science Ltd. All rights reserved.