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Selected fungi, Trichoderma sp., Aspergillus niger, and Fusarium sp., capable of degrading PAHs, were immobilized in a hybrid carrier of polyvinyl alcohol (PVA), sodium alginate, and activated carbon to test their degradation of pyrene and benzo(a)pyrene. The immobilized fungi were inoculated into soil slurry to degrade pyrene and benzo(a)pyrene, with the free fungi as comparisons. Interactions of the fungi were also investigated by using the fungi in pairs or a triad. Immobilized cells of Trichoderma sp., Aspergillus niger, and Fusarium sp. degraded 63, 49, and 69% of pyrene and 34, 29, and 37% of benzo(a)pyrene after 240 h of incubation from an initial 100 mg kg1concentration of pyrene and benzo(a)pyrene, respectively. These degradation efficiencies were much higher than those obtained by the free fungi. The immobilized fungi of Aspergillus niger + Fusarium sp. exhibited the best degradation of 81% pyrene and 43% benzo(a)pyrene, demonstrating a synergistic effect of the microbial organisms contributed to further degradation of PAHs. Immobilized fungi showed a better resistance to the environmental stresses compared to the free cells. Immobilized Aspergillus niger + Fusarium sp. was much more resistant to the environmental stresses (soil pH = 4, or 9; temperature = 15, or 40°C) than the others. Scanning electron micrographs (SEM) of the bead matrix structures proved the advantages of the immobilized microbial technique for soil remediation. These results revealed that the immobilized fungi were more efficient than the freely suspended cells for the biodegradation of PAHs in soils. [ABSTRACT FROM AUTHOR]