Optimization and Characterization of Lead Bioremediation by Strains of Microbacterium Oxydans

Bioremediation as a bioprocess has great potential to reduce the toxicity of heavy metals such as lead (Pb) from contaminated sites. In this study, the Pb-bioremediation potential of Microbacterium oxydans CM3 and CM7 (individually and a mixture of both strains) was evaluated. To improve the Pb-bioremediation efficiency, the response surface methodology (RSM) was used to optimize the process factors responsible such as pH, temperature, and initial Pb concentration. The optimum condition for strain CM3 was observed at pH 6.81, temperature 35.31 °C, the Pb concentration of 337.35 mg/L, and the Pb removal was 60.42%. However, the strain CM7 showed the maximum Pb remediation at temperature 35.65, pH 5.28, the Pb concentration of 346.95 mg/L and the Pb removal was 59.05%. Among the studied bacteria, mixture culture (containing both strains) was more able to remove Pb than a single culture. Our result found that the Pb was precipitated as insoluble form at pH≥6.5 by M. oxydans strain CM3 and insoluble Pb-phosphate compound in the cell wall was confirmed using SEM and EDS. This study revealed that M. oxydans strain CM3 and CM7 have a high Pb remediation potential and could be used to remove Pb(II) from contaminated environments.