Enzyme mediated bacterial biotransformation and reduction in toxicity of 1:2 chromium complex AB193 and AB194 dyes

A bacterial consortium was developed and applied for the treatment of 1:2 chromium complex azo dyes. Fed batch process was studied with optimized conditions for the decolorization of AB193 and AB194 up to 1100-1400 mg L-1 of cumulative dye concentration without further nutrient addition. Fed batch adapted consortium showed 39 and 42% enhanced decolorization for AB193 and AB194, respectively as compared to unadapted consortium. After bio-degradation of the dyes, chromium was not detected in the medium supernatant where as chromium was found sorbed on bacterial cell biomass. During the decolorization process laccase, lignin peroxidase, tyrosinase, azoreductase and NADH-DCIP reductase enzymes were found to be induced. HPLC and FTIR analysis data confirmed the biodegradation of both the dyes. Biodegradation pathways were proposed on the basis of H-1 NMR and GC-HRMS analysis along with role of induced enzymatic system in the degradation process. 45-66% stimulation in growth was observed for Sorghum bicolor and Cicer aeriatinum when biodegradation products of both the dyes were used. Reduction in toxicity on S. aureus and P. aeruginosa was recorded in the range of 58-100% and 43-100%, respectively. (C) 2017 Published by Elsevier B.V. on behalf of Taiwan Institute of Chemical Engineers.