Applied Fundamental Research On Rapid Degradation Of Rice Straw

As one of the main measures for comprehensive utilization of plant fiber waste,straw mulching plays an important role in increasing soil fertility,reducing fertilizer use and improving agricultural ecological environment.In order to improve the existing problems of straw mulching like long cycle and low efficiency,the recombinant Trichoderma reesei(Trichoderma reesei ZJ-09)is studied on rapid degradation of rice straw.Also,the synergetic degradation of rice straw by Trichoderma reesei ZJ-09,Aspergillus niger ZU-06 and Coriolus versicolor is explored.the result showed that Trichoderma reesei ZJ-09 was able to adapt to a wide range of humidity(60%?75%)and temperature(24??32?)during the solid state fermentation(SSF),and the decomposition of the straw could be accelerated after pretreated with 10%ammonia for 24 h.Furthermore,Trichoderma reesei ZJ-09 in straw substrate can grow rapidly and secrete cellulase,xylanase and laccase during the SSF:filter paper activity(FPA)and CMC activity peaked on the 12th day,reaching 132.26 IU/g and 11144.50 U/g,respectively;Laccase and xylanase activity peaked at 8.11 IU/g and 5504.10 IU/g,respectively,on the 10th day.The study of straw degradation process showed that Trichoderma reesei ZJ-09 biodegraded straw with high efficiency and the degradation rate of cellulose,hemicellulose and xylose was 77.93%,55.12%and 31.52%respectively on the 10th day of the fermentation.Trichoderma reesei ZJ-09 was compared with the original strain and Bacillus subtilis regarding the degradation rate,exhibiting 45.40%higher than that of the original strain and 76.37%higher than that of Bacillus subtilis.The result of synergetic degradation of rice straw by Trichoderma reesei ZJ-09 and Aspergillus niger ZU-06 showed that on the 10th day of fermentation,the degradation rates of cellulose,hemicellulose and xylose were 74.49%,63.61%and 56.58%respectively and the total mass loss was 56.01%.The cellulase and xylanase activity in the subtract increased significantly due to the ?-glucosidase and xylanase with high activity produced by Aspergillus niger ZU-06.As a result,FPA,CMC and xylanase activity were 212.07 IU/g,19755.44 U/g and 6053.97 IU/g,which increased by 83.82%,46.62%and 9.97%respectively compared with that achieved by Trichoderma reesei ZJ-09 only.The laccase activity in the subtract was 4.67 IU/g.Though the laccase activity was lower than that of Trichoderma reesei ZJ-09,the lignin degradation rate was much higher than that in the process of single Trichoderma reesei ZJ-09 fermentation.It indicated that the high degradation rate of cellulose and hemicellulose could promote the degradation of lignin.The straw degradation rate and enzyme activity were higher when the inoculation ratio of Trichoderma reesei ZJ-09 and Aspergillus niger ZU-06 is 5:1 and Aspergillus niger ZU-06 is inoculated two days latter after the inoculation of Trichoderma reesei ZJ-09.The result of synergetic degradation of rice straw by Trichoderma reesei ZJ-09 and Corioltus versicolor showed that on the 10th day of fermentation,the degradation rates of cellulose,hemicellulose and xylose were 72.73%,60.72%and 68.21%respectively and the total mass loss was 49.45%.Though the mass loss was lower than that achieved by Trichoderma reesei ZJ-09,the laccase activity was much higher than that in the process of single Trichoderma reesei ZJ-09 fermentation.Laccase activity peaked on the 10th day,reaching 17.37 IU/g,increased by 114.18%,which was significant for soil bioremediation.FPA,CMC and xylanase activity on the 10th day of fermentation were 245.75 IU/g,10659.86 U/g and 6592.60 IU/g respectively.The inoculation volumes of Trichoderma reesei ZJ-09 and Coriolus versicolor were both 12%(v/w).Improved degradation rate was observed when Coriolus versicolor vwas inoculated one day latter after the inoculation of Trichodermareesei ZJ-09.The result of synergetic degradation of rice straw by Trichoderma reesei ZJ-09,Aspergillus niger ZU-06 and Coriolus versicolor showed that on the 10th day of fermentation,the degradation rates of cellulose,hemicellulose and xylose were 77.93%,79.47%and 78.49%respectively and the total mass loss was 60.60%.The peak value of FPA,CMC,xylanase and laccase activity were 300.02 IU/g,20965.38 U/g,8365.59 IU/g and 15.443 IU/g respectively.It indicated that the strains of Trichoderma reesei ZJ-09,Coriolus versicolor and Aspergillus niger ZU-06 played an effective synergistic role in the process of straw degradation.Cellulase,xylanase and laccase with high activity produced during fermentation could accelerate the degradation of straw cellulose,hemicellulose and lignin.This study is of great significance in the rapid degradation of straw for laccase with high activity can be produced in the process of high efficient degradation of straw.A wide range of laccase substrates makes it possible for laccase to degrade many kinds of organic pollutants,which is promising in soil remediation.The results of this study laid a foundation of coupling fast degradation of straw and soil bioremediation.