一株纤维素分解菌的筛选、鉴定及其对玉米秸秆的降解效果

为了筛选具有高效分解玉米秸秆纤维素能力的菌株，采集玉米秸秆还田土样作为样品，并于20℃条件下进行富集培养。利用以玉米秸秆纤维素为唯一碳源的固体分离培养基和刚果红染色法进行初筛，再将筛选到的菌株进行液体发酵培养并取上清液测定酶活，最终获得1株产纤维素酶能力较强的真菌SY-403。结合形态学特征与分子生物学鉴定结果得知，菌株SY-403为蓝状菌属（Talaromyces stollii）。对其所产纤维素酶酶学性质进行初步研究，结果表明，该酶最适反应pH为6.0，最适反应温度为20℃。在模拟室外条件（15℃）下进行秸秆降解试验，玉米秸秆经菌株SY-403处理40 d时，秸秆失重率及纤维素分解率分别达到42.67%、55.26%。利用傅里叶变换红外（Fourier transform infrared，FTIR）光谱技术对降解过程中官能团的变化进行分析，结果表明，纤维素相关谱峰（1 052~1 054 cm-1）相对强度减弱，而羟基相关谱峰（1 328~1 330 cm-1）相对强度增强，这说明纤维素已被分解为可利用的短链结构，即菌株SY-403可用于降解玉米秸秆。

Screening and Identification of a Cellulose Decomposing Fungus and its Degradation Effect on Corn Straw

In order to screen highly efficient cellulose-decomposing strains for corn straw, the soil samples which corn straw was returned in were collected for enrichment culture at 20℃. The initial screening was carried out by solid isolation medium using corn straw cellulose as the sole carbon source and Congo red staining method, and then the culture supernatants of the screened strains through liquid fermentation were collected and used for determination of enzyme activity. At last, fungus SY-403 with strong production of cellulase was obtained. The strain SY-403 was identified as Talaromyces stollii by morphological characterization and the results of molecular biology identification. The study of its cellulase characterization showed that, the optimum reaction pH was 6.0 and the optimum reaction temperature was 20℃. Under the simulated outdoor conditions (15℃), when corn straw was treated with SY-403 for 40 d, the weight loss rate of corn straw and the decomposition rate of cellulose were 42.67% and 55.26%, respectively. Changes of functional groups during the corn straw degradation process were determined by Fourier transform infrared spectroscopy. And the results showed that the peak area of cellulose (1 052~1 054 cm-1) decreased, while the peak area of hydroxyl (1 328~1 330 cm-1) increased, which indicated that cellulose had been broken down into available short chain structures. The results proved that the strain SY-403 could be used to degrade corn straw.