The Research Of Soil Fungal Diversity And Screening Of Degradable Plastics Fungal Strains

Plastics could make convenience to people’s life, but also caused serious environmentalpollution. Biodegradable plastics as a novel environmentally friendly polymer materials arehighly preferred. However, there is the problem of slow degradation in nature.Degradation plastics with microorganism have become a hot area of research inrecent years, because this method has the advantages such as higher degradationefficiency, not harsh reaction conditions and no polluted degradation process.Compared with bacteria and actinomycete, fungi could produce abundant metaboliteswhich could accelerate the hydrolysis of biodegradable plastics. There are many typesof enzymes producing by fungi and most of them are extracellular enzymes, whichcould benefit degrading refractory polymer materials. Therefore, degradable plasticsfungi become the focus of research.Polylactic acid (PLA) is widely used in medicine, industry, agriculture andpeople’s life with its excellent physical, chemical properties and biocompatibility.Actinomycete is considered to be the common biodegradable PLA microbes.Polyvinyl alcohol (PVA) is the main wastewater pollution of textile and chemicfibrous fabrics industry. The degrading strains of it are mainly concentrated onPseudomonas. The production of polyvinyl chloride (PVC) is in the second of plastics.Harmful materials produced during degrading PVC could pollute the environment,while little research about biodegradation of it was done.At present, there are few relevant reports about degradable plastics fungi.Therefore, it is important to screening biodegradable plastics fungal strains anddiscussing the enzymatic properties of degradable enzyme, which has greatsignificance and prospects.In this study, we analyzed the soil fungal diversity in different areas and screenedfungal strains with degradation of PLA and PVA and PVC activity by plate culture.The fermentation conditions of the fungal strains were optimized and the reaction conditions of crude enzyme liquid of it were discussed, which had highest degradationefficiency of PVA.Twenty three soil specimens of environment were collected in nine provinces andautonomous regions. Two hundred and fifteen fungal strains were isolated andidentified by morphology, such as Penicillium, Aspergillus, Mucor, Cladosporium,Trichoderma, Fusarium and Alternaria. Most of the isolates were Aspergillus andPenicillium. These would provide strain resources to screening of degradable plasticsfungal strains.To looking for biodegradable plastics fungal strains, we screened the isolatesusing plate culture with PVA, PLA or PVC as sole carbon source individually.Altogether,27strains had the ability of degrading PVA,18strains had the ability ofdegrading PLA and9strains had the ability of degrading PVC. Among them,3strainshad the ability of degrading three kinds of plastics,4strains had the ability ofdegrading PVA and PLA,5strains had the ability of degrading PVA and PVC.In order to improve the efficiency of biodegradation, we studied the isolatePenicillium exhibition SBF17, optimized the fermentation conditions and discussedthe reaction conditions of crude enzyme liquid. The results showed the most suitablefermentation condition were that the strain cultured7days at25℃with50mL PDBmedium induced by PVA in150mL conical flask. And degradation continues30min at30℃with pH8.0of the reaction system was the most suitable reaction condition ofthe crude enzyme liquid. Under this condition, the crude enzyme activity could up to0.52U/mL, better than the previous reports.The results of this study could provide resource strains and make the foundationfor theory and experiment for the biological degradation of plastics, the development andutilization of enzymes with degradation activity and analysis degradation mechanism.