Microbial decolorization and bioremediation of anaerobically digested molasses spent wash effluent by aerobic bacterial cultures

Anaerobically digested molasses spent wash (DMSW) is a dark-brown-coloured recalcitrant effluent which has a high chemical oxygen demand (COD) and high pollution potential. Bacterial enrichment cultures were set up to obtain isolates capable of DMSW decolorization and bioremediation. Two aerobic bacterial cultures LA1 and D-2 were obtained using soil samples from an Indian distillery plant. Both grew well on 12.5% diluted digested spent wash supplemented with glucose as a readily available carbon source. The optimum conditions for growth and DMSW decolorization were 35 degrees C, pH 7.0, 3% glucose (w/v) and 0.5% peptone or yeast extract (w/v) in a basal mineral salt medium. The maximum decolorization (36.5% and 32.5%) and COD reduction (41.0% and 39.0%) were achieved for cultures LA1 and D-2, respectively, after 8 days incubation under the stated conditions. The advantages of using such a culture in digested spent wash bioremediation are discussed.