| The biomass contained in agricultural and forestry waste was the most abundant renewable resources on the earth,played an important role in the sustainable development of economy and settlement of the energy crisis.Corn straw occupied an important position in many agricultural and forestry waste.It was reported that China's corn straw annual output could reach 3 tons.However,the utility rate of corn straw was low and about 2/3 of the straw was abandoned or burned,especially in the northeast region.This not only caused a waste of valuable resources,but also caused serious environmental pollution and brought great influence to the local agricultural production and the development of the ecological environment.Therefore,the effective use of corn straw resources have become an urgent affairs.Comparasion of lignin degradation ability of edible fungi was first carried out in this experiment and the results showed that Pleurotus djamor strain had the relatively better lignin degradation ability.In order to further improve the utilization of Pleurotus djamor on corn straw lignocellulose,the experimental conditions for preparation and regeneration of protoplast was investigated.The protoplast mutagenesis conditions of lithium chloride and UV irradiation combined with lithium chloride were determined.Finally,experimental technological system was established for screening mutant strains with efficient utilization of corn straw lignocellulose by compoud mutation of protoplast.Mutant strains with efficient utilization of corn straw lignocellulose was obtained and the ability to degrade corn straw lignocellulose were studied.The main results followed as:1.Lignin degradation ability of 9 strains of edible fungi was compared using Bavendamm-PDA as the screening medium.The results showed that they all were capable of degrading lignin,of which degradation ability of Pleurotus djamor was relatively better and Agrocybe cylindracea was the weakest.2.Efficient preparation and regeneration system of Pleurotus djamor protoplast were established and preparation and regeneration conditions were optimized,cell age of 6 d,enzymes of combination 2% lywallzyme with 2% snail enzyme,the ratio(m/V)of mycelia to enzyme of 120 mg/mL,hydrolysis temperature of 30 ?,pH 6.0,hydrolysis time of 3.0 h,the yield of Pleurotus djamor protoplast was 4.2×107 cells/mL under this condition.On this basis,regeneration of the protoplasts by monolayer spread method was carried out in the optimum regeneration medium CPM.Protoplast regeneration rate was 0.53%.3.The mutagensis curve of Pleurotus djamor protoplasts using LiCl and UV irradiation combined with LiCl were depicted.8 w of UV lamp,20 cm of distance from protoplasts,30 s of irradiation,0.3% of concentration of LiCl,the lethal rate reached 83.45%.4.Compoud mutation of ultraviolet irradiation combined with LiCl on Pleurotus djamor protoplasts was carried out.14 mutant strains with faster growth rate than the parental strain was screened by growth rate and antagonistic experiment.Then 5 mutant strains with faster growth rate than the parental strain was screened further using corn straw powder medium.ISSR-PCR was carried out to identiy the 5 mutant strains and the results showed that 4 strains had genetic differences with parental strain as new mutant strains,CM1,CM12,CM13 and CM17.The growth rate of strain CM17 was the best.The strains had good genetic stability after subculture.5.The degradation ability of 4 screened strains to corn straw was determined,the results showed that degradation rate of lignin,cellulose and hemicellulose of strain CM17 were 13.79%,17.61% and 21.29%,respectively,which was 1.33 times,1.44 times and 1.22 times than parental strain.The enzyme activity of MnP,Lip,Lac,Cel and Xyl were 26.21 U/g,15.40 U/g,1.02 U/g,21.90 U/g and 5.43 U/g,respectively,which was 1.06 times,1.08 Times,1.19 times,1.12 times and 1.11 times than parental strain. |
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