中文摘要：

为了实现来源于Streptomyces sp．FAl的木聚糖酶的高效胞外分泌表达，对E．coli BL21（DE3）／pET20b（＋）／coe／xynA基因工程菌的发酵产酶诱导条件进行优化，获得最优的诱导条件为25℃发酵6h后添加终浓度为0．4mmol／L的IPTG。在此基础上对发酵培养基进一步优化，得到最优培养基成分为：甘油11g／L，酵母粉24g／L，蛋白胨8g／L，磷酸盐浓度89mmol／L，镁离子4mmol／L。最终酶活达到780．2U／ml，为未优化前的2．2倍，是目前大肠杆菌摇瓶发酵产木聚糖酶的最高表达水平，为实现该酶的工业化生产奠定基础。

英文摘要：

In order to achieve high production of the xylanase, the optimization of culture medium was investigated in E. coli BI21 （DE3） harboring the plasmid pET20b （ ＋ ）/coe/xynA. The optimized medium and induction condition were as follows ： 11 g/L glycerol, 24 g/L yeast extract, 8 g/L peptone, 89 mmol/L P043, 4 mmol/L Mg2＋ , induced by 0.4 mmol/L IPTG at 6h of culture. Under this condition, the enzyme activity increased from 346.8 U/ml to 780.2 U/ml, which Was 2.2 times as high as that when it was not optimized.