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The Diversity Of Plastic Degrading Fungi In Deep-Sea Sediments And Preliminary Study On The Degradation Mechanism Of Waterborne Polyurethane By A Deep-Sea Fungus Cladosporium Halotolerans 6UPA1

Posted on:2022-02-27Degree:MasterType:Thesis
Country:ChinaCandidate:S YangFull Text:PDF
GTID:2480306341976879Subject:Microbiology
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Use three common plastic wastes(polyurethane(PU),polystyrene(PS),polyethylene terephthalate(PET))as the substrates to enrich plastic-degraing fungi from the deep-sea sediments of the East Pacific Ocean.The results showed that there were differences in the fungal community structure between the plastic-enriched samples and the original sediment samples of the control group.And with the extension of the enrichment time,the alpha diversity of the fungal community in the same plastic enrichment sample,including species richness and Simpson diversity,exhibited significant differences.The OTU Venn diagram shows that the number of shared OTUs between the first round plastic enrichment samples and the original sediment samples is generally higher than the number of shared OTUs in the second round enrichment samples.In addition,the number of OTUs shared by PS and PET enrichement cultures is always greated than the number of OTUs shared by PU and them whatever in the first or second round enrichment.The?diversity analysis also showed that there was no significant difference in fungal communities between PS and PET enriched fungal communities.The results of fungal quantitative q PCR showed that the abundance of fungi in the PU enriched samples after the second round enrichment was significantly higher than that of the original sediments.FUNGuild was applied to predict fungal functions in the community.The results showed that all samples investigated were mainly composed of saprophytes,and the relative abundance of various fungal ecological types in PS and PET enriched samples had no significant difference,but PU enrichement samples showed significant difference with PS and PET samples.The OTU network diagram shows that compared with the PS and PET enriched cultures,the interaction between different OTUs in the PUenrichment culture is denser.The OTU ecological types that form a mutual relationship in PU cultures are also denser than those of the PS and PET cultures.Moreover,ANOVA analysis shows that changes in plastic types can have a significant impact on fungal alpha and beta diversity than prolonging the cultivation time.An efficient PU degrading fungus Cladosporium halotolerans 6UPA1 was isolated from the PU enrichment cultures.The fungus can grow on a solid plate with an aqueous PU(Impranil DLN)as the substrate,and a clear transparent circle is formed around the fungal colony.Almost 100%of PU(0.3%V/V,Impranil DLN)was completely degraded by the fungus after 3 days of incubation at 28?.Growth and CO2production of the fungus with PU as the sole carbon source was investigated.The results showed that the CO2gas production continued to increase within four weeks,indicating that the fungal strain can metabolize and mineralize PU for growth.Infrared spectroscopy analysis of PU culture solution by the fungus showed that the absorption(1,733 cm-1)of the C=O stretching vibration of the carbonyl ester bond basically disappeared,suggesting that the degradation of PU by the strain involves the hydrolysis of the ester bond.The preliminary enzymatic properties of the PU degrading enzyme of Cladosporium halotolerans 6UPA1 were studied.The results showed that the PU degrading enzyme produced by the fungus was extracellular inducible,the optimal temperature for the enzymatic activity was 40?,and the optimal p H was 6.0.After incubating for 1 hour under the condition of p H less than 4or greater than 8,the enzyme activity is basically lost.The typical serine protease inhibitor PMSF has a significant inhibitory effect on the enzymatic activity,while the metalloenase inhibitor EDTA and the cysteine hydrolase inhibitor iodoacetic acid have no effect on the enzymatic activity.The crude enzyme solution of the strain possesses esterase and urease activity,but no protease activity.In summary,our research results confirmed that the deep-sea sediments of the East Pacific contain biodegradable plastic fungi resources,and successfully isolated a fungi Cladosporium halotolerans 6UPA1 that can degrade waterborne polyurethane.
Keywords/Search Tags:marine fungi, plastics, biodegradation
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