BIODEGRADATION OF HERBICIDE ATRAZINE BY PVA-IMMOBILIZED MICROCOCCUS LUTEUS AD3

A high efficiency atrazine-degrading bacterium, Micrococcus luteus AD3, was isolated from the mixture of industrial wastewater and sludge. Polyvinyl alcohol (PVA) was used as a gel matrix to immobilize the strain AD3. Factors affecting atrazine degradation by immobilized cells, such as atrazine concentrations, temperature, and pH, and operational stability of immobilized cells, were investigated. The results showed that under the optimal conditions (30℃、pH 7.2、atrazine 500mg/L) immobilized cells had a higher atrazine degradation rate than that of free cells. Immobilized cells were cultured at 15℃ for 72 hours in minimal medium containing 500mg/L of atrazine (pH 7.2), the atrazine degradation rate was 90%. However, at the same conditions, the degradation rate by free cells was only 35%. Immobilized cells were cultured at pH 5.0, 30℃ for 72 hours in minimal medium containing 500mg/L of atrazine, the atrazine degradation rate was 96%. However, at the same conditions, the degradation rate by free cells was only 40%. Immobilized cells were capable of degrading 1000mg/L atrazine in minimal medium, while free cells were unable. Stability test revealed that immobilized cells can be used repeatedly for at least 30 times without significant decrease in atrzaine degradation activity.