Optimization Of Lignocellulosic Degradation Enzyme Production By P.Chrysosporium And Effect Of Corn Straw Degradation

Corn straw is an important renewable biomass resource with abundant yield and great potential for development.Therefore,how to reasonably transform and treat these straw is an important issue to be solved at present.Microbial method has become a hot research spot in straw pretreatment because of its low cost and safe and effective degradation of straw.In order to achieve the purpose of reasonable and effective degradation of crop straw lignin,a strain of Phanerochaete chrysosporium which produces lignocellulase was obtained by screening,and then enzyme production capacity and the culture conditions for degrading straw were optimized,finally,with the optimal culture conditions,the degradation rate and the change of microstructure of the strain on corn stalk were determined in this study.It provides reference basis for efficient degradation and resource utilization of straw.(1)By measuring the enzyme production capacity of five strains of fungi,one strain with both lignin enzyme and cellulase was screened out as P.chrysosporium.The activity of lignin peroxidase reached the maximum of 2.44 U/L on the 5 d.The activity of manganese peroxidase reached the maximum of 183.56 U/L on the 3 d.The activity of laccase reached the maximum of 11.67 U/L on the 4 d.The activity of cellulase activity reached the maximum of 20 U/m L on the 4 d.The morphological and qualitative study of P.chrysosporium showed that the growth of P.chrysosporium entered the logarithmic phase at 60h and entered the stable phase at 168 h,which could make guaiacol-PDA medium brownish red.(2)The orthogonal optimization and complete combination experiments were carried out on the fermentation conditions of lignocellulase production by P.chrysosporium from five aspects:straw particle size,nitrogen source type and concentration,p H value,metal ion type and concentration,inoculation amount.The results showed that the optimal combination for enzyme production of P.chrysosporium was as follows:100mesh of straw,ammonium nitrate 2.056 g/L,p H 6,Mn SO₄·H₂O 0.433 g/L,inoculation amount of 8 pieces.At the same time,lignin manganese peroxidase reached the maximum value of 606.59 U/L on the 8 d.The maximum value of peroxidase was 70.07 U/L on the 6 d.The maximum value of laccase at 2 d was 19.44 U/L.Cellulase reached the highest value of 14.82 U/ml on the 6 d.(3)The degradation rate of hemicellulose,cellulose,and lignin was 14.81%,30.50%and 27.27%respectively after solid-state fermentation of corn straw for 20 days under the optimal culture conditions.Determination of straw humus composition changes,the results showed that the PQ increased by 24.57%,the carbon content of HLA and FLA increased,while the carbon content of HLM decreased,indicating that P.chrysosporium effectively degraded lignin to form humus.SEM,XRD and FTIR were used to analyze the microstructure changes of corn straw.It was found that the apparent structure of corn straw was destroyed by P.chrysosporium,the relative crystallinity of corn stalks decreased,and lignin demethylation reaction occurred.