Removal Of Heavy Metal Cr(?)by Trichoderma HamatumBSL01

Heavy metal chromium is widely used in industries such as leather,printing,dyeing,textiles,and organic synthesis.The generated Cr(?)is directly discharged into the environment,causing serious pollution to regional water bodies and ecosystems even endangering human health.This article systematically studies the removal of Cr(?)from water by fungi.Using Cr(?)as a specific screening agent,a strain of tolerant Cr(?)was screened and isolated from the soil of Northeast Forestry University experimental forest and named as BSLO1.The strain BSL01 microstructure has distinct and dense branches.There are septa and the nucleus is not clear.The diameter of the mycelium is 2-3 ?m.The length of the specific ITS gene fragment of this strain was 571 bp,the molecular biology identified BSLO1 and the homology of the Trichoderma hamatum to 99.5%.Based on its colony morphology,mycelium morphology,and molecular biological results,the selected strain was identified as Trichodermca hamatum,The minimal inhibitory concentration of Cr(?)against BSL01 was 500 mg/L,which was higher than other Trichoderma fungi reported.At 30? and pH 9.0,the removal efficiency of Cr(?)by fungi BSL01 was over 90%.By determining Cr(?)and Cr(?)contents in the body and culture fluids,it was determined that BSLO1 removed 86.4%of Cr(?)in a bioreduction,and 8.13%of Cr(?)was removed by biosorption and bioabsorption.When the pH value was 7.0-9.0,the removal rate of Cr(?)by BSL01 was over 90%,and the removal rate of Cr(?)reached 94.53%at 25-35?.,BSL01 mycelia surface is rough,mycelia adhered,and spores were wrinkled,rough and aggregated under the concentration of 200 mg/L-500 mg/L.Two BSL1 spore-immobilized beads were prepared by the embedding agent PVA-SAand PVA-SA-PDA,and microscopic observation confirmed that the spores of the immobilized spheroids could germinate and form hyphae.The removal efficiency of Cr(?)by PVA-SA immobilized BSL01 pellets was 93.4%.After 18 times of repeated use,the immobilized beads were lysed and the cells were leaked;Cr(?)was fixed by immobilizing BSL01 spore beads with PVA-SA-PDA.The efficiency is 97.2%,and it can be reused for 23 times.The mechanical properties of the ball are relatively stable and there is no phenomenon of cracking or bacterial leakage.The two immobilized beads start from the 8th cycle and completely remove 50 mg/dL Cr(?)in 3 days,nearly 2 times the removal efficiency of Cr(?)from the free bacteria.The content of reactive oxygen species(ROS)in BSL01 increased.The activities of SOD,POD and CAT were detected in Cr(?)and BSL01.When Cr(?)concentration exceeds 100 mg/L,the ROS content in BSL01 cells increased and the activity of antioxidant enzymes in cells increased.Among them,SOD activity was enhanced by 65.8 U/g,POD activity was enhanced by 93 U/g,and CAT activity was enhanced by 476 U/g.The activity of antioxidant enzymes in BCZ04 cells with non-tolerant Cr(?)also increased,but the overall activity was lower than that in BSL01.The content of malondialdehyde in both fungal cells was increased with Cr(?)concentration.increase.Cr(?)can increase the activity of antioxidant enzymes and remove ROS in BSL01 cells within a certain Cr(?)concentration range.In non-tolerant Cr(?)fungi BCZ04 cells,the antioxidant enzyme activity was lower than that of BSL01 tolerant to Cr(?),so we concluded that the tolerance of the fungus BSL01 to Cr(?)is related to the antioxidant mechanism in the cells.The way to remove Cr(?)from BSL01 is to reduce it to Cr(?).The BSL01 intracellular fluid extract and extracellular excretion fluid were collected and both showed Cr(?)reductase activity;total protein was secreted by concentrating BSL01 cells.SDS-PAGE electrophoretograms showed that the expression of proteins with molecular weights of 30 kDa and 35 kDa was significantly increased under Cr(?)-containing culture conditions,indicating that BSL01 reduced Cr(?)was dependent on reductase in fungal cells.