Heavy metal tolerance of fungal and bacterial isolates, and their functional groups following biosorption

Abstract

Heavy metal contamination still prevails due to improper discharge of effluents from industries, mining activities, agricultural and domestic sources. Hence, the objectives of this study were to isolate bacteria and fungi with high potentials for biosorption of Cd(II), Pb(II), Cr(III) and Ni(II) and to explore their functional groups. Bacteria and fungi able to grow in the presence of 0.1% of selected heavy metals were isolated and enumerated using nutrient agar and potato dextrose agar, respectively. The isolates were then screened for their abilities to withstand high concentrations of heavy metals. After the screening, the isolates with high potential were identified and used for percentage biosorption study. Fourier transform infrared spectroscopy was used to compare the spectra and functional groups elaborated by the control and the metal stressed isolates. Bacterial counts were higher than the fungal counts across the soil samples. Screening revealed that the isolates tolerated Pb(II) and Cr(III) better than Ni(II) and Cd(II). The isolates with high biosorption potentials were identified as Ochobactrum intermedium, Bacillus subtilis, Aspergillus niger and Cunninghamella bertholletiae. The functional groups common to the infrared spectra of the control flasks of C. bertholletiae, A. niger and O. intermedium were primary alcohol, aliphatic primary amine, aromatic amine, imine/ oxime, thiol, sulfone and phenol while aliphatic ether, alkyl aryl ether, conjugated ketone, cyclic alkene, α, β-unsaturated ketone, sulfoxide, aromatic ester, isothiocyanate, secondary alcohol, tertiary alcohol, sulfonamide, sulfonate, allene, amine, conjugated acid and conjugated aldehyde were among the functional groups produced in the presence of heavy metals. The findings conclude that the isolates demonstrated a reasonable binding affinity for heavy metals and can be used in developing biosorbent at a commercial level for Cd(II), Pb(II), Cr(III) and Ni(II).

Keywords

• heavy metal
• tolerance
• sorption
• microorganisms
• functional groups