Biosorption of cadmium using indigenous bacteria isolated from soil contaminated with cadmium

Minh Thi Trana, C.-W. Songa and J.-U. Leea

a Department of Energy and Resources Engineering, Chonnam National University, Korea

minhminhtran94@gmail.com

Expansion of industrialization causes unexpected release of various contaminants into ecosystem, and especially heavy metals pose a threat to environment and human health even with low concentrations. In the present study, we isolated and characterized Cd-tolerant indigenous bacteria from paddy soil around a coal-fired power plant in Korea for potential applicability to remediation. The studied soil contained Cd of 6.0~8.8 mg/kg after aqua regia digestion which is above Korean soil quality criteria. The 16S rRNA sequencing for two indigenous bacteria, G17-1 and G17-2, isolated under the condition of 100 mg/L of Cd revealed that they belonged to Enterobacter ludwigii and Escherichia vulneris, respectively. They appeared to have high minimum inhibitory concentrations for Cd (2,500 and 2,250 mg/L, respectively) which are higher than the other bacteria previously reported. Experiments of Cd biosorption with the two bacteria were conducted using living and dead bacteria. Dead bacteria were prepared using autoclave. When 100 mg/L of Cd was applied at pH 6.8, living G17-1 and G17-2 reduced 51.1% and 41.2% of dissolved Cd, respectively. However, dead bacteria showed 33.7% and 35.8% of Cd removal efficiency, respectively. Input of 300 mg/L of Cd led to lower biosorption capacity than 100 mg/L for both bacteria. The results indicated that the studied Enterobacter ludwigii has high potential of being employed in bioremediation of Cd-contaminated water. Using the isolated strains, applicability to and tolerance against other heavy metals such as Pb, Cu, Ni and Zn will be investigated for further study.

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