| To obtain cellulose-decomposing strains, and to use them for decomposition of rice straw and rice hull, a cellulose-decomposing strain YN1 was isolated from cattle and sheep feces compost. The morphologic and ITS gene sequence analysis suggested that YN1 was Aspergillus sp.Through liquid fermentation conditions optimization, the optimal liquid medium and conditions are:carbon source CMC-Na, nitrogen source NH4NO3, activator Ca2+ temperature 30℃, pH 6.0, RPM160r/min, liquid volume 100 mL, and inoculum age 4 d. Endoglucanases, and the total cellulase activities reached to maximum at the 3th day, and they were 95.7 and 26.6 U/mL respectively, which increased to 1.29 and 1.36 times after optimization.Through solid fermentation conditions optimization, the optimal carbon source is rice hull:rice straw(mass ratiol:4), nitrogen source is NH4NO3, solid:liquid is 1:2(50 g:100 mL). Though solid fermentation, the 2 kinds of cellulase activities reached to maximum at the 5th day, and they were 1192.2 and 210.7 U/g respectively, which increased to 1.33 and 1.26 times after optimization.In the study of characteristics of cellulases, the optimal reaction temperature was at 70℃and the optimal reaction pH was at 4.0 (in a 30-min reaction period). The cellulase activity retained above 80% when the celluases were treated under the conditions that the temperature was from 30℃to 50℃for 1h or the pH from 3.0 to 4.0 for 2 h, which showed the celluases produced by YN1 have resistance to heat and acid.In the degrading experiment, YN1 could degrade 41.87% of rice straw,31.59% of rice hull in weight in 7 d respectively; The remarkable phenomenon that YN1 degrading crude cellulose could be observed by scan electron microscope; YN1 could be mix-cultured with other cellulose-decomposing strains and promote synergy between strains, hence enhancing the degradation of cellulose. YN1 could break down crude cellulose effectively, and showed value of practical applications in rice straw and rice hull decomposition. |
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