Decolorization of azo dyes under saline conditions was studied with Shewanella aquimarina, which demonstrated good growth at up to 7% NaCl. No inhibition on acid red 27 (AR27) decolorization was caused by 1-3% NaCl. Additionally, 14.5% AR27 (0.2mM) could still be removed in 12h in the presence of 10% NaCl. The relationship between specific decolorization rate and AR27 concentration followed Michaelis-Menten kinetics (K(m)=0.34 mM, V(max)=6.44 μmol mg cell(-1) h(-1)). Lactate and formate were efficient electron donors for AR27 decolorization. The initial decolorization rate was in direct proportion to biomass concentration (0.18-0.72 g l(-1)). Compared to NaCl, slighter inhibitive effects were found with Na(2)SO(4) whereas more severe inhibition was caused by NaNO(3). Lower NaCl concentration stimulated azoreductase, laccase and NADH-DCIP reductase activities of cell extracts. AR27 decolorization products were found to be aromatic amines, which were less phytotoxic than the untreated dye.