Decolorization of Textile Reactive Dyes by Bacterial Monoculture and Consortium Screened from Textile Dyeing Effluent

Dyeing effluents have become a vital source of water pollution. Due to the xenobiotic properties and toxicity to all life forms including humans, removal of undesirable color and associated toxicity is crucial. In this study, five dye decolorizing bacteria were isolated from dyeing effluent using selective enrichment culture in Bushnell-Haas (BH) medium amended with co-substrate (i.e. glucose, yeast extract) and 100 mg L^-1 of each commercially available reactive dyes viz. Novacron Orange FN-R, Novacron Brilliant Blue FN-R, Novacron Super Black G, Bezema Yellow S8-G and Bezema Red S2-B. The isolated bacteria were identified and assigned as Neisseria sp., Vibrio sp., Bacillus sp., Bacillus sp. and Aeromonas sp. based on their phenotypic (cultural, morphological, physiological and biochemical characteristic) observation. The dye decolorization efficiency was estimated spectrophotometrically up to 6 days of static incubation at 37 °C and observed that all of the isolates were unable to induce decolorization in absence of co-substrate. In case of monoculture, decolorization percentage varies from no visible decolorization (Bezema Red S2-B by Ek-5) to highest 90% decolorization (Novacron Brilliant Blue FN-R by Ek-13) whereas the decolorization percentage of bacterial consortium varies from 65% (Bezema Yellow S8-G) to 90% (Novacron Brilliant Blue FN-R and Novacron Super Black G). The study outlines the co-substrates mediated decolorization process where bacterial consortium proved as efficient dye decolorizer than that of the monocultures. This finding confers possibility of using novel microbial consortium for biological treatment of disreputable dyeing effluents.