Biodegradation Capabilities of Paraquat-Degrading Bacteria Immobilized on Nanoceramics.

The biodegradation of paraquat was investigated using immobilized microbial cells on nanoceramics fabricated from nanoscale kaolinite. Pseudomonas putida and Bacillus subtilis , which degrade paraquat, were immobilized separately on nanoceramics (respectively called IC nc -P and IC nc -B). The attachment of bacteria to nanoceramics resulted from electrostatic force interactions, hydrogen bonding, and covalent bonding (between the cells and the support materials). The initial 10 mg L -1 concentration of paraquat in water was removed by the adsorption process using nanoceramics at 68% and ceramics at 52%, respectively. The immobilized cells on the nanoceramics were able to remove approximately 92% of the paraquat within 10 h, whereas the free cells could only remove 4%. When the paraquat was removed, the cell-immobilized nanoceramics exhibited a significant decrease in dissolved organic nitrogen (DON). IC nc -B was responsible for 34% of DON biodegradation, while IC nc -P was responsible for 22%. Ammonia was identified as the end product of ammonification resulting from paraquat mineralization.