Bioremediation of heavy metals by using bacterial mixtures

Environmental pollution by heavy and toxic metals because of mining, metallurgic processes, and other chemical industries is a worldwide problem affecting both human health and the environment. The aim of this study was to investigate the synergistic effect of bacterial mixtures on the bioremediation of a mixture of Pb, Cd, and Cu from contaminated soils. Compared to the single culture method, the bacterial mixtures showed higher growth rate, urease activity, and resistance to heavy metals. Four bacterial strains were isolated and identified from bacterial mixtures—Viridibacillus arenosi B-21, Sporosarcina soli B-22, Enterobacter cloacae KJ-46, and E. cloacae KJ-47, which obtained from an abandoned mine site in Korea and showed effective microbially induced calcite precipitation (MICP). The following parameters were monitored during the course of the experiment: optical density, pH, urease activity, calcite production, tolreance to heavy metals, and impermeability test. Synergistic effects on the remediation of various heavy metals via modification of the bacterial mixtures were observed and, after 48 h, remediation of 98.3% for Pb, 85.4% for Cd, and 5.6% for Cu were recorded. Compared with single strain cultures, the bacterial mixtures demonstrated greater resistance and efficiency for the remediation of heavy metals. Thus, our results show that the use of bacterial mixtures is useful in the bioremediation of heavy metals from the contaminated environment.