Rose S H, van Zyl W H
Department of Microbiology, University of Stellenbosch, South Africa.
Appl Microbiol Biotechnol. 2002 Mar;58(4):461-8. doi: 10.1007/s00253-001-0922-3.
The xylanase II (xyn2)- and endoglucanase I (egl)-encoding regions of Trichoderma reesei QM6a were successfully expressed in Aspergillus niger D15 under the transcriptional control of the glyceraldehyde-6-phosphate dehydrogenase (gpd) promoter from A. niger and the glaA terminator of Aspergillus awamori. A stable xyn2 transformant produced beta-xylanase activity of 8,000 nkat/ml and 5,000 nkat/ml in shake-flask cultures containing defined or 20% (v/v) molasses medium, respectively. The recombinant Xyn2 enzyme expressed highest activity at pH 5-6 and 50-60 degrees C and retained more than 75% of its activity after 3 h of incubation at 50 degrees C. A stable egl transformant produced endo-P-1,4-glucanase activity of 2,300 nkat/ml in shake-flask cultures containing defined media and about half the activity in 20% molasses medium. Maximum endoglucanase activity was obtained at pH 5 and 60 degrees C. Both Xyn2 and EgI retained >80% activity after incubation at 50 degrees C for 3 h. The heterologous Xyn2 and EgI represent a significant portion of the total extracellular proteins produced.
里氏木霉QM6a的木聚糖酶II（xyn2）和内切葡聚糖酶I（egl）编码区在黑曲霉甘油醛-6-磷酸脱氢酶（gpd）启动子和泡盛曲霉glaA终止子的转录控制下，在黑曲霉D15中成功表达。一个稳定的xyn2转化体在含有限定培养基或20%（v/v）糖蜜培养基的摇瓶培养物中分别产生8000 nkat/ml和5000 nkat/ml的β-木聚糖酶活性。重组Xyn2酶在pH 5-6和50-60℃时活性最高，在50℃孵育3小时后仍保留其活性的75%以上。一个稳定的egl转化体在含有限定培养基的摇瓶培养物中产生2300 nkat/ml的内切-β-1,4-葡聚糖酶活性，在20%糖蜜培养基中的活性约为一半。内切葡聚糖酶的最大活性在pH 5和60℃时获得。Xyn2和EgI在50℃孵育3小时后均保留>80%的活性。异源Xyn2和EgI占所产生的总细胞外蛋白的很大一部分。
