Evaluation of molasses-melanoidin decolourisation by potential bacterial consortium discharged in distillery effluent.

Abstract

The extracted sugarcane molasses-melanoidins showed the presence of Mn (8.20), Cr (2.97), Zn (16.61), Cu (2.55), Fe (373.95), Pb (2.59), and Ni (4.18mgL-1) along with mixture of other organic compounds which have endocrine-disrupting chemicals (EDCs) properties. A consortium of aerobic bacteria comprising Klebsiella pneumoniae (KU321273), Salmonella enteric (KU726954), Enterobacter aerogenes (KU726955), and Enterobacter cloacae (KU726957) showed the optimum decolourisation of molasses-melanoidins up to 81% through co-metabolism in the presence of glucose (1.0%) and peptone (0.2%) as a carbon and nitrogen source, respectively. The absorption spectrum scanning by UV-visible spectrophotometer between 200 and 700nm revealed reductions of absorption spectrum of organic compounds present in bacterial degraded sample of melanoidins in range of 200-450nm compared to control. The degradation and decolourisation of melanoidins by bacterial consortium was noted by induction of manganese peroxidase and laccase activities in sample supernatant. Furthermore, the TLC and HPLC analysis of bacterial decolourised melanoidins also showed degradation and reduction of absorption peak at (295nm), respectively. Furthermore, FT-IR and GC-MS analysis also showed the change of functional group and disappearance of ion peaks. This indicated the degradation and depolymerisation of melanoidins and cleavage of C=C, C=O and C≡N conjugated bonds which resulted in reduction of colour. The metabolic analysis also showed the disappearance of some organic compounds and generation of new metabolites. Furthermore, the seed germination test using Phaseolus mungo L. showed toxicity reduction in decolourized effluent.