Evaluation of Bacterial Potential for Degradation of Textile Dye

Abstract

Being one of the major sources of environmental pollution highly colored textile efflu ents are a matter of great concern nowadays. Reactive azo dyes are among the most important and widely used textile dyes. Effective and eco-friend ly treatment of these dyes can be achieved by the process of bioremediation of which bacterial mediated degradation being fast and efficient is very important. The present study was conducted to evaluate the potential of native bacterial species for the degradation of a reactive textile dye i.e. Reactive Blue 221 (RB 221). Bacterial strains were isolated from a texti le industry sludge sample by enrichment technique. Screening was done after which efficient decolorizers were identified and then optimized for the degradation of RB 22l. Out of the total 27 isolates, 6 most proficient RB 22 I decolorizing bacterial strains that showed upto 80% decolorization, under static condition were selected for the further studies. These strains were identified as Pseudomonas sp. BDS2 Alcaligenes sp. BDS9, Micrococcus lute us BDS17, Arthrobacter sp. BDS13, Corynebacterium sp. BDS20 and Pseudomonas aeruginosa BDS23. These strains displayed effi cient growth and decolorization activity in glucose and yeast extract (0 .1 %) supplemented Mineral salt medium (MSM). Optimum pH and temperature ranges were 7-8 and 30-37°C respectively. Under these conditions, at an inoculum size of 10%, the 6 selected isolates showed upto 90% decolorization of 50 ppm of RB 221. These bacterial strains showed different levels of dye tolerance in the range of 50-250 ppm. The isolates were also tolerant to different NaCI concentrations and P. aeruginosa BDS23 displayed the maximum salt tolerance (upto 6% NaCI) along with efficient decolorization activity (83%). The strains also showed appreciable color removal ability in the presence of some metal compounds e.g. CuCh, CoCh and CdCh. Corynebacterium sp. BDS20 and P. aeruginosa BDS23 were found to be the most efficient decolorizers. They were followed by M luteus BD~ 17, Pseudomonas sp. BDS2, Arthrobacter sp. BDS 13 and lastly Alcaligenes sp. BDS9. UV-Vis and FTIR spectroscopy indicated that decolorization was achieved by biodegradation or by a combination of adsorption and biodegradation. Finally the non-toxic nature of degradation metabolites was revealed by phytotoxicity and cytotoxicity assays.