This study was aimed to enhance the PAH biodegradation rate by repeated-batch treatment using immobilized Phanerochaete chrysosporium. In batch operations, the degradation rates of anthracene and pyrene in their mixture were 1.74 and 1.67 mg/L·day, respectively. Repeated-batch operations were composed of two steps. The first step was to increase the concentration of immobilized cells using the growth medium, and the second step was to degrade the PAHs in another type of medium for PAH degradation. For cell immobilization, celite bead (100~500 ㎛) was used as the support material. To obtain high cell concentrations, the composition of the growth medium and growth conditions were optimized. As a result, 28.0∼30.0 g/L of cell concentration was obtained in the first step, which corresponded to 109∼118 mg-cell/g-bead of cell loading. In the repeated-batch operations with 30 mg/L of pyrene, the maximum degradation rate was 6.58 mg/L·day. As the number of batch increased, the cell concentration of immobilized cells significantly decreased, and the degradation rate and specific activity gradually increased to a maximum value and then decreased. To revive PAH degrading activity and cell mass, cultivation using the growth medium instead of the PAH-degrading medium was carried-out just for one batch. This led to a significantly recovered cell mass and specific activity although not to the original levels. In the repeated-batch operations for degrading anthracene, a similar trend was observed. The maximum degradation rate was 5.36 mg/L·day. In the repeated-batch operations for degrading anthracene and pyrene simultaneously, the degradation rates for both of them were lower than those when they were treated separately. The maximum degradation rates of pyrene and anthracene were 4.29 and 4.46 mg/L·day, respectively. These values were about 2.5 times higher than those in the batch treatment above.
