Study on degradation pattern and properties about in situ degradation mechanism of biodegradable polymer

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The contribution of fungi to the microbial degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)films in soil was studied. Various traces, cavities and grooves, observed on the dented surface of PHBV films demonstrated that the degradation was a concerted effect of a microbial consortium colonizing on the film surface including fungi, becteria and actinomycetes. The succession of microbial consortia in the soil around the PHBV films during the degradation showed a distinctive increase in the fungal population resulting in its dominance. Comparison of the degradation ability of microbial strains isolated from the soil, where PHBV films were degraded, revealed that fungi showed the highest contribution to the PHBV degradation in soil, where they grew very rapidly along the film surface with their high degradation ability and then expanded their hyphae in a three-dimensional manner.Fungal degradation of poly(3-hydroxybutyrate-co-3-hydroxyvalerate)(PHBV)film in soil was described mathematically in terms of the surface growth rate of fungal hyphae and the degradation ability of fungal depolymerase. the surface growth rate of fungi was derived from the notion of equivalent symmetric tree model and was expressed for the two different growth phases, i.e., exponential phase and deceleration phase. The proposed growth and degradation models represented well the experimental data obtained from fungal PHBV degradation in soil. Fungi degrade PHBV film with the formation of soil aggregate that gives the advantageous condition for fungal growth and PHBV degradation. Fungal degradation rate of PHBV film in soil depends on the population of colonized fungal biomass on PHBV film surface and their degradation ability