Screening of a straw cellulose-degrading fungi QSH3-3 and study on its characteristics of cellulase production

In order to obtain the high effective straw cellulose-degrading microorganism, A cellulose-degrading fungi strain QSH3-3 was isolated from the rotten leaves and soil through methods of decolour congo red and decomposing filter paper, It was classified as Penicillium oxalicum QSH3-3 according to the analysis of its morphology and 18S rRNA gene sequences. The culture condition of cellulase production of stain QSH3-3 was studied under liquid fermentation condition. The results showed that the best carbon source was alkali-pretreated corn straw supply (5%), and the best nitrogen was （NH4）2SO4 supply (0.2%). The optimal conditions for cellulase production were as follows: the initial pH 6.5, the inoculation number 5%, the cultivation temperature 30℃, the cultivation time 4 d. Under these optimum conditions, the activities of FPase, CMCase and Xylanase were 12 U, 30 U and 605 U（U indicated unit of enzyme activity）, respectively. Their residual enzyme activities can up to 70% to 80% of the peak value at low temperature 15℃ and over 70% at initial pH ranged from 4 to 9. Experimental results on the stability and properties of enzyme showed that FPase, CMCase and Xylanase had high activity and stability from pH 4 to 9 with residual enzyme activities for over 85%. Activities of FPase, CMCase and Xylanase were unstable when the temperature is above 45℃. These results indicated that strain QSH3-3 had developing potential to be used for the straw-returned-native-field.