Palladized biomass of Desulfovibrio vulgaris (Bio-Pd(0)) reduced Cr(VI) to Cr(III) at an initial rate four-fold higher than chemically-prepared Pd(0) metal. Optimal Cr(VI) reduction by suspended Bio-Pd(0) occurred at pH 3, whereas pH did not affect the rate of Cr(VI) reduction by Bio-Pd(0) immobilized in agar beads. The rate of Cr(VI) reduction was concentration-dependent below 300 mu mol dm(-3), and application of enzyme kinetics, considering Bio-Pd(0) as an 'artificial enzyme', gave an apparent K-m (K-m (app)) of approx. 650 mu mol dm(-3) and V-max of 1667 nmol h(-1) mg Pd(0) for suspended Bio-Pd(0). The potential of Bio-Pd(0) as a method for the treatment of Cr(VI) -wastes is discussed. (c) 2005 Society of Chemical Industry.