Abstract

A xylanase from Streptomyces rochei L10904 was purified and characterized. The enzyme was enriched to apparent homogeneity by ammonium sulphate precipitation and CM Sepharose Fast Flow ion exchange, with an apparent molecular weight of 22.5 kDa. The purified xylanase was non-covalently immobilized on Eudragit S-100 in order to produce xylo-oligosaccharides, and found to retain at least 98.9% of its activity in this application. The immobilized xylanase exhibited a shift in optimal pH from 6.5 to 7.2 while the optimal temperature was increased from 65 to 70 °C. The half-time of immobilized xylanase was 50% higher than that of the free xylanase and the storage stability of the immobilized enzyme was also improved. The end-products produced from hydrolyzing a pre-treated bean stalk substrate were mainly xylobiose and xylotriose, and the total content of XOS (DP = 2 ∼ 5) was up to 85% for the immobilized xylanase after incubating at 50 °C for 24 h, without any xylose being detected. Immobilized xylanase retained about 60% of its initial catalytic activity after 5 successive cycles of hydrolysis.

摘要

来自罗氏链霉菌的木聚糖酶L10904 被纯化和表征。该酶通过硫酸铵沉淀和 CM Sepharose Fast Flow 离子交换富集至表观均一性，表观分子量为 22.5 kDa。纯化的木聚糖酶非共价固定在 Eudragit S-100 上以生产低聚木糖，并发现在该应用中保留了至少 98.9% 的活性。固定化木聚糖酶的最佳 pH 值从 6.5 变为 7.2，而最佳温度从 65 °C 增加到 70 °C。固定化木聚糖酶的半衰期比游离木聚糖酶高50%，固定化酶的储存稳定性也得到提高。经预处理的豆秆基质水解产生的最终产物主要是木二糖和木三糖，固定化木聚糖酶在 50°C 下孵育 24 小时后，XOS（DP = 2 ∼ 5）的总含量高达 85%，未检测到任何木糖。固定化木聚糖酶在连续 5 个水解循环后保留了其初始催化活性的 60%。