Microbial degradation of di-n-butyl phthalate by Micrococcus sp immobilized with polyvinyl alcohol

Di-n-butyl phthalate (DBP) is an endocrine-disrupting chemical and priority pollutant which is difficult to remove by conventional activated sludge process. In this study, a very efficient DBP-degrading strain was isolated and identified as Micrococcus sp. The microbial degradation of DBP by immobilized Micrococcus sp. was investigated. Polyvinyl alcohol (PVA) gel was used as an immobilizing material for entrapment of microbial cells. The degradation of DBP by cells of Micrococcus sp. immobilized by different PVA gel beads was investigated, including PVA-boric acid beads, PVA-sodium nitrate beads, and PVA-orthophosphate beads. The experimental results showed that the PVA-orthophosphate immobilized cells was most efficient for DBP degradation, in comparison with freely suspended cells and the cells immobilized in PVA-boric acid and PVA-sodium nitrate. The PVA-orthophosphate immobilized cells could be reused for more than 12 cycles without losing its degradation capacity; they were more tolerant to pH and temperature changes than freely suspended cells. The kinetics of DBP degradation by immobilized Micrococcus sp. conformed to the first-order kinetic model. The metabolic mechanism of immobilized cells remained unchanged.