Department of Process Engineering, University of Stellenbosch, Private Box X1, Matielend, Stellenbosch, 7602, South Africa.
World J Microbiol Biotechnol. 2012 Jan;28(1):113-9. doi: 10.1007/s11274-011-0798-z. Epub 2011 Jun 2.
Thermoascus aurantiacus is able to secrete most of the hemicellulolytic and cellulolytic enzymes. To establish the xylanase inducers of T. aurantiacus, the mycelia were first grown on glucose up until the end of the exponential growth phase, followed by washing and re-suspension in a basal medium without a carbon source. Pre-weighed amounts of xylose (final concentration of 3.5 mg/ml), xylobiose (7 mg/ml) and hydrolyzed xylan from sugarcane bagasse (HXSB) which contained xylose, xylobiose and xylotriose (6.8 mg/ml) were evaluated as inducers of xylanase. It was observed that xylose did not suppress enzyme induction of T. aurantiacus when used in low concentrations, regardless of whether it was inoculated with xylobiose. Xylobiose promoted fast enzyme production stopping after 10 h, even at a low consumption rate of the carbon source; therefore xylobiose appears to be the natural inducer of xylanase. In HXSB only a negligible xylanase activity was determined. Xylose present in HXSB was consumed within the first 10 h while xylobiose was partially hydrolyzed at a slow rate. The profile of α-arabinofuranosidase induction was very similar in media induced with xylobiose or HXSB, but induction with xylose showed some positive effects as well. The production profile for the xylanase was accompanied by low levels of cellulolytic activity. In comparison, growth in HXSB resulted in different profiles of both xylanase and cellulase production, excluding the possibility of xylanase acting as endoglucanases.
橙色嗜热丝孢菌能够分泌大多数半纤维素酶和纤维素酶。为了建立橙色嗜热丝孢菌的木聚糖酶诱导剂，首先将菌丝体在葡萄糖上培养至指数生长阶段结束，然后用无碳源的基础培养基洗涤和重新悬浮。评估了木糖（终浓度为 3.5mg/ml）、木二糖（7mg/ml）和甘蔗渣水解木聚糖（HXSB）作为木聚糖酶诱导剂。HXSB 中含有木糖、木二糖和木三糖（6.8mg/ml），结果发现，当木糖以低浓度使用时，无论是否接种木二糖，都不会抑制橙色嗜热丝孢菌的酶诱导。木二糖促进了快速的酶产生，在 10 小时后停止，即使碳源的消耗率很低；因此，木二糖似乎是木聚糖酶的天然诱导剂。在 HXSB 中仅测定了可忽略不计的木聚糖酶活性。HXSB 中的木糖在最初的 10 小时内被消耗，而木二糖则以较慢的速度部分水解。用木二糖或 HXSB 诱导时，α-阿拉伯呋喃糖苷酶诱导的谱非常相似，但木糖诱导也有一些积极的影响。木聚糖酶的产生谱伴随着低水平的纤维素酶活性。相比之下，在 HXSB 中生长导致木聚糖酶和纤维素酶生产的不同谱，排除了木聚糖酶作为内切葡聚糖酶的可能性。
