焦曲霉产木聚糖酶的研究

Studies on Xylanase Produced by Aspergillus ustus

从１１４４株真菌中筛选到一株产木聚糖酶活力较高的焦曲霉（Ａｓｐｅｒｇｉｌｕｓｕｓｔｕｓ）。该菌株适宜的产酶条件为在４％麸皮液中添加０５％葡萄糖，０４％硝酸钠及０１％氯化钠，３０℃振荡培养６ｄ，木聚糖酶活力可达２１７６ｕ／ｍＬ。酶反应的最适温度为５５℃，最适ｐＨ为５５，在ｐＨ５～８酶活力稳定。４５℃保温１ｈ，酶活力剩余３５％。酶水解桦木木聚糖的Ｋｍ值为４３×１０－３ｇ／ｍＬ，Ｖｍａｘ值为４９ｍｇ／（ｍＬ·ｍｉｎ）。酶解产物以木三糖和木四糖为主，表明该酶是一种典型的内切糖苷酶。

Aspergillus ustus showing high xylanase activity was isolated from 1144 strains of fungi.The medium for the optimal xylanase production(4% wheat spelt,0.5% glucose,0.4% NaNO 3 and 0.1% NaCl)yielded 2176 u/mL within 6 days of cultivation at 30℃.The enzyme showed a temperature optimum of 55℃ and retained 35% of activity after incubation at 45℃ for 1 h.The enzyme also showed a pH optimum of 5.5 and was stable in the range of pH 5.0 to 8.0.The K m value and V max value calculated were 4.3×10 -3 g/mL and 4.9 mg/(mL·min) for birchwood xylan,respectively.The hydrolysis products from birchwood xylan were xylotriose and xylotetraose.Thus,the enzyme is considered to be an endoglycosidese.