Study On Screening And Biological Function Of Producing Laccase Fungus In Alpine Meadow

Laccase,lignin peroxidase and manganese peroxidase together constitute lignin degrading enzyme system,which plays an important role in the formation of humus and organic matter in soil.In order to explore and discover the resources of low-temperature resistant laccase-producing fungi in alpine grassland soil and further understand the role of laccase in the transformation of soil organic matter in alpine grassland.In this paper,four aspects of the research including screening of soil laccase-producing fungi,biological characteristics of fine strains,enzymatic properties of laccase and mineralization of soil organic matter were studied.The research results are as follows:1.The 9 strains of fungi isolated from soil of alpine grassland were used as the research object while ITS-rDNA method for molecular identification and substrate colorimetry to screen.The results showed that strain 1.9 was Uncultured fungus clone,2.1a Scytalidium,310b Marasmius tricolor,2.1c Saccharicola,2.3a fungal sp,2.4d Saccharicola,10a Marasmiusrotalis,3.7c Alternaria,WB Verticillium longisporum.Except for strain 3.7c,the other 8 strains basically produced oxidative bands on culture medium with guaiacol,anthrone,ortho-toluidine and benzidine as substrates.Laccase activity assay showed that the laccase activity of strain 310b was 1.62 IU,which was the highest compared with the other 8 strains,and the difference was significant?P<0.05?.2.The strain with the highest laccase activity,Marasmius tricolor 310b,was selected as the research object,under different conditions?temperature,carbon source,nitrogen source,pH and salt concentration?to measure the colony growth diameter,and it turns out,the selected strains 310 b growing fastest under the condition of 30?,pH of 4.8 and not adding NaCl,and the difference was significant?P<0.05?;With no carbon source as the control,the colony grew fastest after adding sucrose and dextrin?P<0.05?;Lysine and urea had obvious growth inhibition to the strain?P<0.05?.3.The laccase activity of strain Marasmius tricolor 310b was measured under the condition of different temperatures,initial pH,metal ions,and nonnutritive organics.The results show that the optimal reaction temperature of the strain 310b was 35?and the higher enzyme activity was maintained in the range of 0-45?;The optimum pH was 4.5 and the higher enzyme activity was maintained in the range of 4.0-7.0.Compared to the control,Fe²⁺and Fe³⁺inhibited the enzyme activity?P<0.05?;Ethanol can increase enzyme activity?P<0.05?,nevertheless,acetonitrile,H₂O₂,SDA and EDTA had inhibitory effects on the enzyme activity?P<0.05?,in which H₂O₂ had the strongest inhibitory effect,and the addition of acetone had no effect on the enzyme activity.4.The soil CO₂ emission,soil organic carbon mineralization rate,soil organic carbon content,soil microbial biomass carbon content and soil microbial respiration entropy were determined.The results showed that above indicators were higher than the control group after adding the laccase-producing fungus strain 310b.Both of them showed regular changes,indicating that the laccase produced by the laccase-producing fungus strain 310b promoted the formation and transformation of soil organic matter.