摘要：AbstractThere have been several researches on the bioremediation of heavy metals using microorganisms. However there is paucity of information on the use of synergistic heavy metal tolerant bacteria and fungi for the bioremediation of heavy metals.Bacillus megateriumandRhizopus stoloniferisolated already and identified to tolerate lead, cadmium and nickel contamination were selectively investigated for heavy metal bioremediation.B. megateriumwas exposed to 3200 mg/L each of PbCl2, NiSO4and CdCl2whileR. stoloniferwas exposed to 3200 mg/L of PbCl2, NiSO4but 800 mg of CdCl2. Furthermore, the two organisms were exposed to 1500 mg/L of all the three metals (comprising 500 mg/L of each heavy metal) for 96 hrs at 30 °C. At the end of the study, the synergistic growth ofR. stoloniferandB. megateriumhad the maximum uptake of Pb (541.50 mg). Also the individual growth ofB. megateriumandR. stoloniferhad the highest uptake of Ni (501.05 mg) and Cd (479.10 mg) respectively. The highest uptake of the combined heavy metals was byB. megaterium. For individual metal contaminations, the synergistic growth of the microbes led the highest loss of Pb (25.24%) and the lowest loss of Ni (40.41%). In the case of the combined metal contamination, the synergistic growth of the microbes suppressed the bioremediation efficacy ofB. megateriumand improved the efficacy ofR. stolonifer. There was slight negative correlation between the pH and the percentage loss of the heavy metals from the medium (p = 0.885) and between the optical density and percentage heavy metal loss (p = 0.901). The results showed the effectiveness of these organisms for heavy metal bioremediation and consequently, their potential as bioremediation agents in polluted environments individually and in a synergistic growth and that such occurs through bioaccumulation.
