Degradation of remazol black B by bacillus cereus strain A from textile wastewater

Abstract

Five bacterial strains designated as A, B1, B2, C and Y1 that were revived from the UTM glycerol stock were used for biodegradation study of azo dyes (SF BLACK EXA, SF RED 3BS, SFN BLUE 150 % and SF YELLOW EXF) at three different conditions; aerobic, facultative anaerobic and partial aerobic (without agitation). Screening test shows bacterium A, under facultative anaerobic condition demonstrated the highest decolourisation rate with removal rate (7.0% h-1) of 0.1 gL-1 SF BLACK EXA was observed. Relationship of growth and decolourization analysis shows decolourisation rate of the same azo dye by bacterium A in CDM medium under facultative anaerobic and aerobic conditions were 26.445% h-1 and 24.56% h-1, respectively. The growth rate of bacterium A was found higher in aerobic culture (2.733 mgh-1) in comparison with that in facultative anaerobic culture (1.067 mgh-1). In other assessment, bacterium A was applied into optimized CDM medium (glucose (1 gL-1), NH4Cl (0.5 gL-1), K2HPO4 (7 gL-1), KH2PO4 (2 gL-1), MgSO4.7H2O (0.1 gL-1), CaCl2 (0.02 gL-1), RBB (0.1 gL-1)), pH 6.5, incubated at 35 °C, with 10 % v/v inoculum under facultative anaerobic condition. Result showed that bacteria A successfully degraded more than 80 % RBB after 20 h incubation. Degradation of RBB molecules increased up to 90 % and 30 % COD removal before attaining stable condition within 164 h incubation. Azoreductase analysis revealed that enzyme was produced intracellularly (11.45 x 10-3 Umin-1) and stabled at pH 6-8 and temperature ranged from 30 ºC to 40 ºC. HPLC analysis revealed that biodegradation of RBB under combined facultative anaerobic-aerobic condition produced sulfanilic acid (Rt = 3.988 min) after 160 h incubation and two unknown metabolites (Rt = 6.071 min and 7.480 min) after 164 h incubations. The partial 16S rRNA analysis showed that bacterium A closely related to Bacillus cereus (99 % sequence similarity). These findings suggest that this bacterium has the capability to assist in the degradation of wastewater containing azo dyes from industry of textile-based.