Coelho Glauciane Danusa, Carmona Eleonora Cano
Departamento de Bioquímica e Microbiologia, Instituto de Biociências, UNESP, 13506-900, Rio Claro, SP, Brasil.
J Basic Microbiol. 2003;43(4):269-77. doi: 10.1002/jobm.200390030.
An Aspergillus giganteus strain was isolated as an excellent producer of xylanase associated with low levels of cellulase. Optimal xylanase production was obtained in liquid Vogel medium containing xylan as carbon source, pH 6.5 to 7.0, at 25 degrees C and under shaking at 120 rpm during 84 h. Among the several carbon sources tested, higher xylanase production was verified in xylan, xylose, sugar-cane bagasse, wheat bran and corn cob cultures, respectively. Optimal conditions for activity determination were 50 degrees C and pH 6.0. The xylanolytic complex of A. giganteus showed low thermal stability with T(50) of 2 h, 13 min and 1 min when it was incubated at 40, 50 and 60 degrees C, respectively, and high stability from pH 4.5 to 10.5, with the best interval between 7.0 to 7.5. This broad range of stability in alkali pH indicates a potential applicability in some industrial processes, which require such condition. Xylanolytic activity of A. giganteus was totally inhibited by Hg(+2), Cu(+2) and SDS at 10 mM. The analysis of the products from the oat spelts xylan hydrolysis through thin-layer chromatography indicated endoxylanase activity, lack of debranching enzymes and beta-xylosidase activity in assay conditions.
分离出一株巨大曲霉，它是一种优秀的木聚糖酶产生菌，纤维素酶水平较低。在以木聚糖为碳源、pH值为6.5至7.0、25℃、120 rpm振荡培养84小时的液体Vogel培养基中可获得最佳木聚糖酶产量。在所测试的几种碳源中，分别在木聚糖、木糖、甘蔗渣、麦麸和玉米芯培养物中验证了较高的木聚糖酶产量。活性测定的最佳条件为50℃和pH 6.0。巨大曲霉的木聚糖分解复合物热稳定性较低，在40、50和60℃下孵育时，其T(50)分别为2小时、13分钟和1分钟，在pH 4.5至10.5范围内稳定性较高，最佳区间为7.0至7.5。这种在碱性pH范围内的广泛稳定性表明其在某些需要这种条件的工业过程中具有潜在的适用性。巨大曲霉的木聚糖分解活性在10 mM时被Hg(+2)、Cu(+2)和SDS完全抑制。通过薄层色谱法对燕麦麸木聚糖水解产物的分析表明，在测定条件下存在内切木聚糖酶活性，缺乏去分支酶和β-木糖苷酶活性。
