Decolourisation and detoxification of synthetic molasses melanoidins by individual and mixed cultures of Bacillus spp.

The decolourisation of synthetic melanoidins (i.e., GGA, GAA, SGA, and SAA) by three Bacillus isolates (Bacillus thuringiensis (MTCC 4714), Bacillus brevis (MTCC 4716) and Bacillus sp. (MTCC 6506)) was studied. Significant reduction in the values of physicochemical parameters was noticed alongwith the decolourisation of all four melanoidins (10% v/v). B. thuringiensis (MTCC 4714) caused maximum decolourisation followed by B. brevis (MTCC 4716) and Bacillus sp. (MTCC 6506). A mixed culture comprised of these three strains was capable of decolourising all four melanoidins. The medium that contained glucose as a sole carbon source showed 15% more decolourisation than that containing both carbon and nitrogen sources. Melanoidin SGA was maximally decolourised (50%) while melanoidin GAA was decolourised least (∼06%) in the presence of glucose as a sole energy source. The addition of 1% glucose as a supplementary carbon source was essential for co-metabolism of melanoidin complex. The decolourisation of synthetic melanoidin by three Bacillus spp. significantly reduced the toxicity to the tubificid worm (Tubifex tubifex, Müller).