| Triphenylmethane dye is a kind of synthetic dye whose parent structure is Triphenylmethane.TPM dyes are difficult to degrade because of their synthetic properties and complex aromatic structures,which persistence in the environment cause a serious threat to the human and ecological environment.In recent years,studies on removal of dyes have mostly focused on the typical species of white rot-fungi from dye-contaminated environments.However,other uncontaminated fungi,such as endophytes,have been poorly reported.According to previous reports,endophytic fungi can metabolize organic pollutants and assist plant growth,thus promoting phytoremediation of polluted environment.In addition,endophytic fungi in extreme environments have been reported to be more resistant to stress.Hence,this study focused on three metal-contaminated plants Sinosenecio oldhamianus and Nephrolepis auriculata,which were used to isolate,purify and identify of endophytic fungi and analyze their diversity.And to screen out endophytic strains that can effectively decolorize TPM dyes,and the decolorization mechanism was preliminarily studied,and the decolorization conditions were optimized to improve the decolorization ability of TPM dyes.(1)A total of 109 endophytic fungi were isolated from 180 tissues of three plants sample by surface-sterilization method.Results showed that they could be divided into23 taxa based on their morphological characteristics and molecular biological identification.The isolates were mainly Ascomycota(78),followed by Basidiomycota(28)and Deuteromycota(3).Additionally,Alternaria sp.and Ceriporia sp.were dominant genera with relative frequencies 46.8%(51 strains)and 19.3%(21 strains),respectively.The alpha-diversity index indicated that the Nephrolepis auriculata has the most abundant species diversity(H'=1.89,D=0.75),Moreover,the?-diversity indexes indicated that the colonization of endophytic fungi had host and tissue specificity.(2)Four TPM dyes were preliminarily decolorized by 109 endophytic fungi.The results showed that 22 strains(nine different genera)were able to decolorize all tested four TPM dyes to different degrees on the solid plate.Isolated SWUSI4 was the best decolorization efficiency for the four tested TPM dyes in the liquid decolorization screening,the decolorization efficiency of strain SWUSI4 on the crystal violet,methyl violet,malachite green and cotton blue was 70%,89%,75%and 90%,respectively.One-way analysis of variance test showed that the decolorization efficiency of SWUSI4on four TPM dyes was significantly higher than other strains(p<0.05).In addition,the strains of Aiternaria sp.and Ceriporia sp.also showed good decolorization efficiency for the four dyes.Moreover,there was no significant difference in decolorization efficiency of the four dyes among different strains of the same genus(p>0.05).Therefore,four strains of different genera(SWUSI4,SWUNF9,SWUSI26 and SWUSO21)were selected to further study the decolorization ability under shaken culture.The results showed that the strain SWUSI4 showed the highest decolorization efficiency for the four tested TPM dyes,and its decolorization efficiency for crystal violet,methyl violet,malachite green and cotton blue was 74%,95%,80%and 92%,respectively.One-way analysis of variance test showed that the decolorization efficiency of strain SWUSI4 and other three strains(SWUNF9,SWUSI26 and SWUSO21)against four TPM dyes was significantly different(p<0.05).Therefore,the decolorization mechanism of strain SWUSI4 was preliminarystudied.(3)To study the mechanisms of decolorization of TPM dyes was performed separately by live cells and dead cells of SWUSI4 in the absence of nutrients culture system.The results showed that the decolorization efficiency of live cells of strain SWUSI4 was significantly higher than that of dead cells.On the other hand,after the decolorization the color of dead cells was same as corresponding TPM dyes,respectively.Fourier infrared spectroscopy(FTIR)analysis revealed the dye interacts with hydroxyl,amino,phosphate,and ester lipid groups in the cell wall of strain SWUSI4.UV–vis adsorption spectra analysis suggested:the complete dissolution of maximum peaks was clearly observed for MV and MG treated with live cells of isolate SWUSI4,for CV and CB treated with live cells,the corresponding maximum absorption peak dramatically decreased in intensity.However,for CV,MV,MG and CB treated with dead cells,the maximum peaks remained detectable after 14 days.The above results indicated that the live cells of SWUSI4 could decolorize through the two mechanisms of biosorption and biodegradation,while the dead cells only via biosorption.(4)Several common factors influencing the decolorization of dye(including initial concentration of dye,biomass dose of strain,temperature,and p H)were studied to find the optimal decolorization conditions of fungus.The results show that when the biomass of strain SWUSI4 was 40g/L,the dye concentration was 100 mg l-1,the temperature was 30?,and the p H was 7,the decolorization efficiency of strain SWUSI4 against the four TPM dyes could reach above 90%after 24h.The activity of Lac,Mn P and Li P was detected 24 hours after decolorization.Our results demonstrated that SWUSI4 produced more Li P and Mn P as their levels were significantly induced compared to controls.Finally,plant toxicology experiments were carried out to analyze the germination rate of plant seeds and the root length and stem length of germinated seeds.The results showed that compared with untreated TPM,the seed germination rate of TPM treated by SWUSI4 was significantly improved,and the root length and stem length of seeds had significant changes(p<0.05).Therefore,strain SWUSI4 has certain application potential in the biodegradation and biological decolorization of triphenylmethane dyes,which can reduce the toxicity of dyes.To sum up,the endophytic fungi of three plant tissues in a polluted factory in Chongqing have relatively rich species diversity,which is similar to the diversity index of endophytic fungi growing in other non-polluted environments.This indicates that the plants growing in the polluted area are still colonized by a large number of endophytic fungi.After screening,the strain SWUSI4 had the best decolorization effect on four TPM dyes under both solid and liquid decolorization.The removal of the toxicity of TPM dyes in the environment mainly by the two mechanisms both bioadsorption and biodegradation.This study is the first to report that the decolorization of TPM dyes by endophytic Bjerkandera adusta SWUSI4.This paper reports the results from this study with aims to provide scientific basis and technical support for the application and popularization of endophytic in dye pollution remediation technology. |
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