Study on a laccase-producing fungus from alpine grassland soil in eastern Qilian Mountains:screening,identification,and activity analyses

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.