Microbial Decolourization of an Anthraquinone Dye C.I. Reactive Blue 19 Using Bacillus cereus

Abstract

Aims: This work aimed at using B. cereus strain to decolourize a textile dye and also to study the influence of various environmental parameters on the decolourization processes. Study Design: Decolourization efficiency of B. cereus. Place and Duration of Study: Department of Microbiology, Ahmadu Bello University, Zaria, Nigeria; Department of Medical Microbiology, Faculty of Medicine, Ahmadu Bello University, Zaria, Nigeria and Department of Textile Science and Technology, Ahmadu Bello University, Zaria, Nigeria, between March 2011 and September 2011. Methodology: The B. cereus strain used was isolated from contaminated food by using a selective media (Mannitol egg yolk polymyxin agar) and then culturing and storing on nutrient agar slants at –20ºC after biochemical tests were done to identify the isolate. All the microbial batch experiments were carried out at ambient conditions in 250ml Erlenmeyer flasks. Nutrient broth was autoclaved at 121ºC at 15psi for 15min and nutrient agar plates were also used in the isolation of the B. cereus strain. Effects of various parameters, including initial dye concentration (0, 0.5, 1.0 and 2.0g/l), glucose concentration (50, 100, 200 and 500mg/l), pH (4.0, 7.0 and 10.0) and temperature (20, 27 and 40ºC), on dye decolourization were investigated. Decolourization extent was determined by measuring the absorbance of the culture supernatant at 591nm using a Unicam UV9100-visible spectrophotometer. Decolourization extent was calculated using a standard equation as specified by Giwa et al., 2011. Results: The bacteria culture exhibited 95% decolourization ability within 72 hours. The optimum dye decolourizing activity of the culture was observed at pH 7.0 and incubation temperature of 27ºC. Maximum dye decolourizing efficiency was observed at 200 mg/l concentration of RB19. The dye solution showed high peak at the wavelength of 591nm. Conclusion: The results thus obtained have characterized and identified the dye degrading ability of the B. cereus. The presence of a co-substrate (glucose) is an essential condition for attaining maximum decolourization efficiency. Reactive blue 19 was completely and rapidly decolourized by B. cereus after 3days of incubation with different effects on the dye as seen in the result.