Performance and kinetic of pesticide residues removal by microporous starch immobilized laccase in a combined adsorption and biotransformation process

Abstract

The control and removal of pesticide residues from possible pollution source by using improved methods without secondary pollution is essential for reducing its potential hazards to humans. In this work, a method of combining adsorption and degradation for the removal of pesticide residue was investigated based on the biodegradable microporous starch immobilized laccase (LA–MPS). Biosorbent of microporous starch (MPS) were prepared from maize starch by treating with glucoamylase and α-amylase to increase the specific surface area. Then, laccase with natural biological activity was immobilized on the surface of MPS, the prepared LA-MSP was characterized by SEM, FT-IR, activity assay and stability test. Moreover, LA–MPS coupled with mediators were applied to remove two typical triazine herbicides, atrazine and prometryn, in paddy field water sample. The physical action force between the LA–MPS and pesticide molecules resulted in the good adsorption of LA–MPS to the two pesticides. The apparent rate constants of laccase interaction with pesticide molecules were greatly improved by the adsorption process. Compared with natural degradation, the removal efficiency of atrazine and prometryn were increased by 61% in 7 days, which contributed by 43∼52% of degradation and 10∼38% of adsorption. These results indicated that the application of LA–MPS prepared by MPS sorbent was a feasible and green approach for the removal of pesticide residues in paddy field water sample.