通过对小麦/玉米秸秆还田土壤样品进行富集培养，利用刚果红纤维素培养基筛选得到产纤维素酶的真菌XJ-25, 并对该菌株进行形态学观察和18S-ITS-5.8S区序列系统发育分析，初步鉴定为格孢腔菌属(Phaeosphaeria)，定名为Phaeosphaeria sp.XJ-25。在研究液体发酵培养基中碳源、氮源、培养时间、起始pH、培养温度、接种量以及通气量对菌株XJ-25的羧甲基纤维素酶(CMC)的酶活及滤纸酶（FPA）的酶活影响的基础上，利用响应面法对发酵条件进行优化。结果显示，CMC酶活达到最大的条件为玉米秸秆粉1.34 g·L-1 (麸皮0.16 g·L-1)、尿素 10.06 g·L-1、培养基初始pH 3.25、接种量 4.13%，CMC酶活达到23.871 U·mL-1。FPA酶活最大的发酵最佳条件为玉米秸秆粉1.34 g·L-1（麸皮0.16 g·L-1）、尿素 10.12 g·L-1、培养基初始pH 3.41、接种量 4.22%，FPA酶活为8.653 U·mL-1。粗酶液的最适反应温度为50℃，酶液的热稳定较差，当温度超过40℃，该酶活力显著下降。最适反应pH为5，在pH 4~6的范围内酶活性较稳定。
A highly active cellulose-decomposing strain XJ-25 was isolated from the soil in the wheat and maize straw returned fields using enrichment culture and Congo red staining test. The isolated strain was identified as Phaeosphaeria sp. XJ-25 by its morphological characteristics as well as by phylogenetic relationships based on 18S-ITS-5.8S ribosomal gene sequences. Conditions for liquid fermentation, a process that produces cellulase were optimized by the response surface methodology (RSM). The results showed that the conditions for CMCase activity reaching the maximum were: the corn stalk powder, 1.34 g·L-1 (bran was 0.16 g·L-1）; urea, 10.06 g·L-1; initial pH of culture medium, 3.25; inoculation quantity, 4.13%; and CMCase activity reached 23.871 U·mL-1. The conditions of FPase activity reaching the maximum were: the corn stalk powder, 1.34 g·L-1 (bran was of 0.16 g·L-1); urea, 10.12 g·L-1; initial pH of culture medium, 3.41; inoculation quantity, was 4.22%; and FPase activity reached 8.653 U·mL-1. The optimal reaction temperature of the crude enzyme solution was 50℃. When the temperature was over 40℃, the thermal stability of enzyme solution was poor, and the enzyme activity significantly decreased. The optimum reaction pH was 5. In the range of pH 4-6, the enzyme activity was more stable.