Decolourization of molasses based distillery wastewater using a bacterial consortium

The effluent from sugarcane molasses based distilleries leads to environmental pollution due to its large volume and the presence of dark brown coloured compounds. In this study, a bacterial consortium isolated from waterfall sediments was selected as a molasses-decolourizing agent. The effect of culture conditions and medium composition on decolourization activity and growth of the bacterial consortium was investigated. The bacterial consortium was able to grow and decolourize molasses wastewater under facultative and anaerobic conditions in general. Aerobic culture conditions at pH 7 and 9 in molasses wastewater containing LB medium exhibited high growth but poor decolourization. The addition of a supplementary nutrient source in molasses wastewater medium significantly increased the decolourization activity of the bacterial consortium by up to 26.5% within 48 h under anaerobic conditions. Comparison of 16S rDNA sequences indicated that the bacterial consortium which showed decolourization activity under aerobic conditions consisted of Acinetobacter sp., Pseudomonas sp., Comamonas sp., Klebsiella oxytoca, Serratia marcescens and unidentified bacteria, whereas, the anaerobically enriched consortium consisted of Pseudomonas sp., Klebsiella oxytoca, Bacillus cereus and Citrobacter farmeri, a mercury-resistant bacterium, and an unidentified bacterium. Denaturing gradient gel electrophoresis profiles indicated that the community structures of aerobically and anaerobically enriched bacterial consortium were different.