一株产纤维素酶的甲醇利用细菌的鉴定及其纤维素降解条件优化

采用刚果红染色法，从废弃矿山周边土壤中筛选出一株产纤维素酶的甲醇利用细菌，命名为xt-04。形态特征、生理试验及16SrDNA序列和gyrB序列分析表明，该菌株属于Bacillusmethylotrophicus。为提高该菌所产纤维素酶的降解能力，首先通过单因子实验考察了底物CMC—Na浓度、反应温度及缓冲液pH值对纤维素酶活力的影响；然后采用响应面分析法对影响纤维素酶活力的3个单因子进行了优化。结果表明，单因素实验得出的适宜反应温度、缓冲液pH和底物浓度分别为70℃、5．0和2％（20mg／mL）；响应面法得出的最高酶活力条件：反应温度、pH和底物浓度分别为66．1℃、4．81和19．01mg／mL。在最优条件下，酶活力达到17．85U／mL，比优化前的酶活力12．84U／mL提高了39．01％。因此，鉴于这种纤维素酶能耐受较高温度和酸性条件，该菌株所产纤维素酶可能在工业中具有良好的应用前景。

Identification and optimal degradation conditions for cellulase-degrading enzyme of a methanol-utilizing and cellulase-producing bacterium

A methanol-utilizing and cellulase-producing bacteria, designated strain xt-04, was isolated from the soil of abandoned mine lands of Hunan Province by Congo red staining test. This strain was identified as the species Bacillus methylotrophicus based on the morphological, physiological characteristics and 16S rDNA and gyrB gene sequences analysis. In order to improve the catalytic ability of the cellulase produced by this strain, influences of the concentration of CMC-Na, temperature and pH on the activity of cellulose-decomposing enzyme were investigated by single factor experiment. Then, response surface analysis was used to optimize the influences of three factors on the ccllulase activity. The results indicated that the appropriate concentrations of CMC-Na, temperature and pH, based on single-factor experiments, were 20 mg/mL, 70 ℃, and 5.0, respectively. And the optimal concentrations of CMC-Na, temperature and pH of cellulase-producing, from response surface analysis, were 19.01 mg/mL, 66.1 ℃ and 4.81, respectively. Under the optimal conditions, the activity of cellulose-decomposing enzyme was improved from 12.84 U/mL to 17.85 U/mL, an increase of 39.01%. Thus, the enzyme produced by strain xt-04 may has an attractive potential for industrial applications in decreasing the current cost of bioconversion of lignocellulose to ethanol by being resistant to acids and retaining activity at higher temperatures.