Cadmium bioremediation by metal-resistant mutated bacteria isolated from active sludge of industrial effluent

ABSTRACT

Bioremediation of metal pollutants from industrial wastewater using metal resistant bacteria is a very important aspect of environmental biotechnology. In this study, three species of Pseudomonas aeruginosa were isolated from active sludge of a food factory in the city of Kerman. The bacterial identity was determined by various biochemical tests. Among them, isolate number one could grow on Muller-Hinton agar medium containing 6mM cadmium ion [Cd[2+]] and was therefore selected for further study. The isolates were subjected to mutation by two mutagenic agents [Acridine Orange and Acriflavine] using gradient plate and SIC techniques. The Minimum Inhibitory Concentration of Cd[2+] for the isolate one after mutation was increased to 7mM. Removal of Cd[2+] using mutated and wild type strains of this bacterium was carried out at different time intervals [10-300 minutes]. It was observed that within 60 minutes, 94.7% of cadmium was removed in 30mg/L of Cd[2+] solution. However, with 60mg/L Cd[2+] solution, only 53.58% and 38.68% Cd[2+] removed were achieved by mutated and wild type bacteria, respectively. The equilibrium data was fitted by Langmuir isotherm equation and the related parameters for Cd[+2] were derived. Based on the data obtained in this study, it can be concluded that biomass of this bacterium can be used for bioremediation of cadmium from industrial waste processing plants with high efficiency