The presence of melanoidins in molasses wastewater leads to water pollution both due to its dark brown color and its COD contents. In this study, a bacterial consortium isolated from waterfall sediment was tested for its decolorization. The identification of culturable bacteria by 16S rDNA based approach showed that the consortium composed of Klebsiella oxytoca, Serratia mercescens, Citrobacter sp. and unknown bacterium. In the context of academic study, prevention on the difficulties of providing effluent as well as its variations in compositions, several synthetic media prepared with respect to color and COD contents based on analysis of molasses wastewater, i.e., Viandox sauce (13.5% v/v), caramel (30% w/v), beet molasses wastewater (41.5% v/v) and sugarcane molasses wastewater (20% v/v) were used for decolorization using consortium with color removal 9.5, 1.13, 8.02 and 17.5%, respectively, within 2 days. However, Viandox sauce was retained for further study. The effect of initial pH and Viandox concentration on decolorization and growth of bacterial consortium were further determined. The highest decolorization of 18.3% was achieved at pH 4 after 2 day of incubation. Experiments on fresh or used medium and used or fresh bacterial cells, led to conclusion that the limitation of decolorization was due to nutritional deficiency. The effect of aeration on decolorization was also carried out in 2 L laboratory-scale suspended cell bioreactor. The maximum decolorization was 19.3% with aeration at KLa = 2.5836 h -1 (0.1 vvm).

ABSTRACT: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.

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