Reduction of sulphonated water-soluble azo dyes by micro-organisms from human faeces

Kinetic study approach of remazol black-B use for the development of two-stage anoxic–oxic reactor for decolorization/biodegradation of azo dyes by activated bacterial consortium

“…Monoazo dye decolorization has been reported to follow firstorder kinetics with respect to dye concentration by several authors [36,30], where as other studies mention zero order [37,38] or even half order kinetics [39]. Furthermore, for the case of diazo and polyazo dyes, only the first part of decolorization profiles has been reported to follow first-order kinetics with respect to the dye concentration [30].…”

“…This biomass was used as inoculum for all batch decolorization experiments. Decolorization was studied using various co-substrates/electron donors (glucose, dextrose, maltose, starch, tryptone, lactose and sucrose), at different dye concentration (25,50,75,100,200, 500, 1000 and 2000 mg l −1 ), temperature (20,25,30,35,37,40 and 50 • C) and pH (5, 6, 7, 8, 9 and 10). pH adjustment was done with 2N KOH or 2N HCl.…”

Kinetic Studies of Reactive Azo Dye Decolorization in Anaerobic/aerobic Sequencing Batch Reactors

“…However, literature information about the kinetics of decolorization and the environmental factors affecting the decolorization rates is relatively scarce. Monoazo dye decolorization has been reported to follow first-order kinetics with respect to dye concentration by several authors (Wuhrmann et al 1980;Carliell et al 1995;Hu 1998; Van der Zee et al 2001a), whereas other reports mention zero-order (Watabe et al 1980;Harmer and Bishop 1992) or even half-order kinetics (Yu et al 2001). Furthermore, for the case of diazo and polyazo dyes, only the first part of the decolorization profiles has been reported to follow first-order kinetics with respect to the dye concentration ( Van der Zee et al 2001a).…”

Azo Dyes and Their Metabolites: Does the Discharge of the Azo Dye into Water Bodies Represent Human and Ecological Risks?

“…After an azo dye is orally ingested, it can be reduced to free aromatic amines by anaerobic intestinal microflora and possibly by mammalian azo reductase in the intestinal wall or the liver (Walker, 1970;Prival & Mitchel, 1982;Umbuzeiro et al, 2005a). Such biotransformations can occur in a wide variety of mammalian species, including both Rhesus monkeys and humans (Rinde & Troll, 1975;Watabe et al, 1980;Prival & Mitchel, 1982; 31 previously mentioned, the main biotransformation products of azo dyes are aromatic amines, and thus a brief description of this class of compounds is shown below.…”

“…They are reduced by azo reductases produced by intestinal bacteria, and to a lesser extent by enzymes from the cytosolic and microsomal fractions of the liver. The first catabolic step in the reduction of azo dyes is the cleavage of the azo bond, producing aromatic amines (Cerniglia et al, 1986), accompanied by a loss of color of the dye, and bacterial azoreductases show much greater activity than hepatic azoreductases (Watabe et al, 1980;Collier et al, 1993;Raffi et al, 1997). This reduction process may produce compounds that are more or less toxic than the original molecule (Collier et al, 1993;Rafii et al, 1997), depending on the chemical structure of the metabolite generated.…”