Azo dye decolorization by Shewanella aquimarina under saline conditions

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 (0.2 mM) could still be removed in 12 h 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 mu mol 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 Na2SO4 whereas more severe inhibition was caused by NaNO3. 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. (C) 2012 Elsevier Ltd. All rights reserved.