产耐高温木聚糖酶菌株的筛选及其产酶条件优化

Screening of thermostable xylanase producing strains and its condition optimization for xylanase production

从牛粪堆肥中分离、筛选到1株产耐高温木聚糖酶的细菌NF1,经形态特征和16S rDNA序列分析,鉴定菌株NF1为类芽孢杆菌,命名为类芽孢杆菌(Paenibacillus sp.)NF1。采用响应面法对该菌种产木聚糖酶的发酵条件进行优化。首先利用Plackett Burman试验设计筛选出影响产酶量的3个主要因素,即牛肉膏浓度、NaCl浓度和初始pH值。在此基础上使用Design-Expert软件进行Box-Behnken试验设计,通过响应面分析得出菌株NF1发酵产酶的最佳条件为玉米芯20g/L、牛肉膏28.2g/L、K2HPO45g/L、MgSO40.5g/L、NaCl 7.1g/L、初始pH值为6.9;装液量40mL、转速160r/min、接种量2%、温度28℃。经过验证试验,优化后粗酶液酶活达到160.6IU/mL,与响应面预测结果一致,较优化前木聚糖酶酶活提高了51.4倍。

A new thermostable xylanase-producing strain isolated from cow dung compost was identified as Paenibacillus sp. NF1 based on the evi- dence from its morphological characteristics and 16S rDNA sequences. Response surface methodology was employed to optimize the fermentation conditions of xylanase by Paenibacillus sp. NF1. Firstly, the important factors influencing xylanase production were identified by the method of Plackett-Burman design including the concentration of beef extract and NaC1, and initial pH value. Then, Box-Behnken design and response surface analysis were used to further investigate the optimal central levels and relationships of these factors. By using the quadratic regression model equation and analyzing the response surface of xylanase production, the optimal fermentation conditions were determined as followed： corncob 20g/L, beef ex- tract 28.2g/L, K2HPO4 5g/L, MgSO4 0.5g/L, NaC1 7.1g/L, initial pH value 6.9, liquid loading quantity 40ml, rotate speed 160r/min, inoculum size 2%, fermentation temperature 28℃. Under these conditions, the production of xylanase was 160.6 IU/mL, which was consistent with the maximum theo- retic value, and was increased by 51.4 times compared to that before optimization.