Microbial Degradation of Phenol in the Presence of Heavy Metal Ion by Immobilized Bacterial Cells

The growth-inhibitory and lethal effects of zinc ion and copper ion on a phenol-degrading microorganism, Acinetobacter calcoaceticus AH strain, was examined by measuring optical density of cells, total cell number, viable cell number and macromolecule contents per cell in a batch culture. The effects of heavy metal ion concentrations on the specific growth rate and the specific change rate of viable cell number were clarified, suggesting that the inhibitory effect of copper ion was stronger than that of zinc ion and the copper ion caused not only the growth-inhibition but also the death of cells. The immobilized cell culture using alginate calcium gel beads as a carrier of cells was more effective for degrading phenol in the presence of a higher concentration of heavy metal ion rather than the conventional liquid culture. The repeated batch culture using immobilized cells could degrade 100 mg/l phenol containing 30 mg/l of zinc ion for 10 batch cultures and therefore provided the attention toward the applications in the effective degradation of phenol in the presence of heavy metal ion.