It is very significant to study the interactions between cellulolytic enzymes because the interactions could increase the decomposition of cellulose.In the paper,five fungal strains from alpine meadow soil were selected to compose a synthetic system.The five fungal strains had the high activities of cellulolytic enzymes.The activities of cellulolytic enzymes of the individual fungal strain or the different mixed fungal strains were determined and the interactions between cellulolytic enzymes in the fungal strains were analyzed.The results showed that compared with the individual strains,the activities of cellulases,Hemicellulase,and laccases in the mixed solutions which were composed of the same volume of enzymes from the two of the five fungal strains decreased(P0.05),and the decreases of these enzyme activities were different.The celluloses and hemicelluloses activities of the mixed enzymes from the 310 b and 23 a strains as well as from the 310 b and H strains changed significantly(P0.05),whereas there were not significant changes in the mixed enzymes of 310 b and 24 d strains as well as in the mixed enzymes of 310 b and 26 B strains.
A fungus strain belonging to Marasmius tricolor has been isolated and selected from the soil of alpine meadow located in eastern Qilian Mountains.To full understand the characteristics of the fungus producing the laccase,three substrates(i.e.,guaiacol,caechol,and o-benzyl aniline) were used to induce the activity of laccase,using substrate spectrophotometry and liquid rotating methods.The temporal order and sizes that the oxidation zones occurred on guaiacol-PDA culture media were analyzed to investigate the relative rates that the fungus produced laccase.The results showed that Marasmius tricolor produced oxidation zones cultured on the media that contained guaiacol,caechol,and o-benzyl aniline,respectively,but the colors and diameter sizes of the oxidation zones and fungus community diameters differed from different media.The diameters of the oxidation zones and fungus community were the greatest when the fungus was cultured on the medium that contained guaiacoI.The fungus showed the greatest activity producing laccase.Guaiacol might induce its hypha to secrete laccases at the early stage of its growth.Laccase activity was the highest when guaiacol was substrate in the reaction system.Laccase produced by the fungus showed the greatest activity under the condition of 30~C and pH 4.5.The enzyme also showed higher activity under the condition of 0~45℃,pH 4.0~6.5.
The sixty-five fungi strains that were isolated from the alpine grassland soil in the eastern Qilian Mountains were researched as the object in this paper.The fungi initially selected through culturing on the medium of guaiacol-PDA andα-naphthol-PDA medium.The fungi with the function to produce laccases was screened(identified as No.310b)based on the growth and colony sizes on the culture mediums of guaiacol, caechol,and o-benzyl aniline,the activities of redox reaction catalyzed by the laccases in these fungi grown,as well as the activity of laccases in these fungi cultured on the stems of oil rape.By rDNA-ITS sequence analysis, the fungus was identified as Marasmius tricolor.Then elementary study on the conditions under which laccases were produced by the fungus(No.310b)was carried out.These results showed that the activity of laccases in the fungus reached the peak when it was cultured under the condition:25℃,initial pH 4.0,sucrose and peptone that were used as carbon and nitrogen resources,respectively.Few non-trophic organic chemicals showed different effects on laccase activity in the fungus.α-naphthol and Tween-80did not have significant effects on laccase activity in the fungus,but guaiacol,tannic acid,and indole acetic acid inhibited the activity of laccases, especiall indole acetic acid,which significantly inhibited laccase activity(P0.01).When Cu2+concentrations ranged from 0.001-0.025g/L,laccase activity increased as the concentrations of Cu2+increased,reaching the peak at 0.025g/L.With the increase of inoculum sizes,laccase activity increased.Ranging from 60to 180 r/min,laccase activity increased.When the amount of the powder of oil rape stems ranged from 0to 1g,laccase activity increased,but when the amount was higher than 1,the activity decreased.
The effects of global changes on grassland ecosystems have become a focus of great concern in the whole world due to natural factors and human activities.The ecological effects of global changes,including elevated CO_2,warming,and increased nitrogen deposition,on grassland ecosystems are complex.The responses of the grassland vegetation and soil environment of plant-site interface to global changes are very sensitive,and there is a close relationship between soil microbial communities and the plant-site interface of grassland ecosystem.The response mechanisms of microorganisms to global changes differ from different levels.The factors of climate changes have direct or indirect effects on soil microorganisms,but the mechanisms are still not clear.The effects of global changes,including elevated CO_2,warming,and increased nitrogen deposition,on the soil microbial community diversities of grassland ecosystems and the response mechanisms of grassland microorganisms to global changes are reviewed in this paper.And the issues and research trends are discussed.
