Decolorization of anthraquinone Vat Blue 4 by the free cells of an autochthonous bacterium, Bacillus subtilis

Uncontaminated soil, Vat Blue 4 contaminated soil and Vat Blue 4 effluent were screened for heterotrophic bacterial population and the bacterial density were found to be 19.3 × 10⁴ Colony Forming Units (CFU)/gm, 5.5 × 10⁴ CFU/gm and 1.1 × 10⁴ CFU/ml respectively. Student's ‘t’ test analysis affirmed that significant variation prevailed between the three set of ‘t’ tests conducted (P<0.001 to 0.002). The heterotrophic bacterial population of dye contaminated soil comprised of 32.5% of Pseudomonas spp. followed by 27.5% of Bacillus spp., 15.0% of Aeromonas spp., 12.5% of Micrococcus spp. and 12.5% of Achromobacter spp. The optimum inoculums load, pH and temperature were found to be 5% (10 × 10⁴ counts), 10 and 35°C respectively. Free cells of B. subtilis decolorized Vat Blue 4 up to 92.30% after 24 hours of treatment. Total Dissolved Solids (TDS), Biological Oxygen Demand (BOD₅) and Chemical Oxygen Demand (COD) were reduced up to 50.00, 79.60 and 75.40% respectively.