Bacterial–yeast consortium as an effective biocatalyst for biodegradation of sulphonated azo dye Reactive Red 198
A novel bacterial–yeast consortium (Brevibacillus laterosporus and Galactomyces geotrichum) acts as a proficient biocatalyst. It decolorized 92% of sulphonated azo dye Reactive Red 198 (RR 198) within 18 h at a dye concentration of 50 mg L−1 as compared to 58 and 42% decolorization using Brevibacillus laterosporus and Galactomyces geotrichum alone, respectively, in the same experimental conditions (pH 7, 40 °C, in static condition). The cumulative action of enzymes such as veratryl alcohol oxidase, laccase, NADH-DCIP reductase and azoreductase in the consortium culture was responsible for dye degradation. Fourier transform infrared spectroscopy and high performance thin layer chromatography analysis of the dye and its extracted metabolites suggested the biotransformation of RR 198 into simple metabolites; whereas the biotransformation of the same by individual microorganisms was different than by consortial biodegradation. According to gas chromatography-mass spectroscopy studies, RR 198 was biotransformed into much simpler compounds such as (ethylsulfonyl)benzene and 1,3,5-triazine by the bacterial–yeast consortium. This metabolic fate of the dye was entirely different in consortium than when compared to individual microbial treatment. Single microbial species could lead to only partial mineralization of the intact dye molecule; whereas, nearly complete degradation of the dye molecule was achieved using the consortium culture. This study clearly suggests that the consortium has an enormous strength to catalyze RR 198 within a short period as compared to individual microbial cultures.