EVALUATION OF MICROBIAL STRIPPING OF DYED COTTON FABRIC

Abstract

Chemical color stripping processes not only reduces the quality of fabric but also induces an extensive attention to expensive treatments and the safe disposal of persistent and toxic chemical wastes. This research project was planned to investigate the potential of the biochemical stripping of cotton fabric that had been dyed with a C.I Reactive Black B dye to a bluish black/grey shade using five indigenous strains of white rot fungi including Pleurotus ostreatsus IBL-02, Phanerochaete chrysosporium IBL-03, Coriolus versicolor IBL-04, G. lucidum IBL-05, and Schizophyllum commune IBL-06 in a Kirk's basal salts medium. The color stripping was measured in terms of color strength (K/S value), before and after treatment. Among the five strains of WRF, G. lucidum IBL-05 showed best stripping in 15 days of incubation under continuous shaking conditions (120 rpm) at pH 4.5 and 35 0C. The biochemical stripping process was optimized by studying the effects of temperature, pH, additional carbon and nitrogen sources, low molecular weight mediators and metal ions on the synthesis of ligninolytic enzymes and the stripping of dyed cotton fabric by G. lucidum IBL-05. The addition of carbon based sources (glucose, starch, glycerol, wheat bran) and nitrogen containing additives (corn steep liquor, maize gluten 60%, yeast extract, peptone), mediators of ligninolytic enzymes (veratryl alcohol, MnSO4, Guaicol, ABTS and H2O2) and metal salts (CuSO4, FeSO4, ZnSO4, Cd (NO3)2, CaCl2) enhanced the formation of ligninolytic enymes by G. lucidum IBL-05 and fabric color stripping. Maximum color stripping (90.59%) achieved by use of the maximum activities of LiP (712 U/mL), MnP (422U/mL) and laccase (82U/mL) was achieved after 15 days of incubation at pH 4 and 350C using Kirk's basal nutrient medium supplemented with wheat bran (1g/100ml) as a carbon source, and peptone (0.2g/100mL) as a nitrogen source, with MnSO4 as a mediator and ZnSO4 as a metal salt. The biological stripping was superior to the chemical stripping process. The effluent generated in chemical stripping was highly polluted as compared to that obtained from the biological process in terms of pH, TSS, DO, BOD, COD and TOC. Biological color stripping is gentle and does not excessively deteriorate the fabric quality or reduce the fabric weight.