Abstract: 【Objective】 The purpose of this experiment was to optimize the optimum enzyme production conditions of a strain of Aspergillus fumigatus producing heat-resistant cellulase, analyze the fiber degradation effect of the enzyme solution on straw, and provide the basis for its application in the biodegradation of cellulose.【Method】 3, 5-dinitrosalicylic acid (DNS) method was used to determine the activities of cellulase produced by Aspergillus fumigatus WL002 from the previous study, and its enzymatic properties were analyzed.The culture conditions and fermentation medium were optimized by the one factor at a time strategy combined with orthogonal test.The crude fiber degradation effects of the crude enzyme on roughage were analyzed by in vitro fermentation.【Result】 Enzymatic characterization analysis revealed that the optimum reaction pH of cellulase produced by WL002 was 7.0, and the residual enzyme activity was 74%-95% and 56%-90% after preservation at pH 6.0-8.0 for 0.5 and 1 h, respectively.The optimal reaction temperature was 60℃, and after holding at 70℃ for 0.5-1.5 h, the residual enzyme activity was 70%-80%.The maximum cellulase production by strain WL002 were achieved with peptone (1.0%) and wheat straw (2.0%) as the best carbon and nitrogen sources, respectively, at pH 7.0, 7% initial inoculum, the incubation time of 48 h and a culture temperature of 50℃, the average cellulase activity reached 3.11 U/mL.The degradation rates of wheat straw and corn straw were 6.1% and 4.7%, respectively, when treated with the crude enzyme produced by strain WL002 for 60 h.【Conclusion】 The cellulase produced by Aspergillus fumigatus WL002 had a wide pH range, strong thermostability and fiber degradability.The proper conditions for producing cellulase of strain WL002 were achieved, which laid a foundation for its follow-up exploitation and application.

Key words: cellulase; Aspergillus fumigatus; enzymatic characteristics; fermentation optimization