实施例5木聚糖酶的酶学性质测定
1、最适作用pH分析
采用pH值分别为2.0、2.5、3.0、4.0、4.5、5.0、5.5、6.0、7.0、8.0的磷酸氢二钠-柠檬酸缓冲液,将实施例4发酵获得的粗酶液进行稀释测定,木聚糖底物也分别用对应pH值的缓冲液配制,在37℃下进行木聚糖酶活力测定,计算酶活,以最高酶活为100%,计算相对酶活,结果显示,本发明提供的木聚糖酶突变体XynA1、XynA2和XynA3的最适作用pH值均为5.5,与野生型木聚糖酶XynPF一致。
2、最适反应温度分析
分别在30℃、35℃、40℃、45℃、50℃、55℃、60℃、65℃、70℃、75℃,pH5.5条件下,对实施例4发酵获得的粗酶液进行木聚糖酶酶活测定,以最高酶活为100%,计算相对酶活,结果显示,野生型木聚糖酶XynPF的最适作用温度为50℃;而本发明提供的木聚糖酶突变体XynA1、XynA2和XynA3的最适作用温度为60℃。
3、耐热性分析
将实施例4发酵获得的粗酶液分别用pH5.5的乙酸-乙酸钠缓冲液稀释至约20U/ml,在65℃、75℃和80℃条件下分别处理5min后,测定其残留酶活,以未处理样品的酶活为100%,计算酶活残留率。
结果如图1所示,野生型木聚糖酶XynPF在65℃条件下处理5min后,仅能保持28%左右的酶活,在75℃、80℃条件下处理5min后,酶活残留率几乎为0;而木聚糖酶突变体XynA1在65℃条件下处理5min后能保持45%以上的酶活,在75℃、80℃条件下处理5min后仍能保持30%和21%左右的酶活,木聚糖酶突变体XynA2和XynA3在65℃条件下处理5min后能保持80%以上的酶活,在75℃条件下处理5min后仍能保持40%左右的酶活,80℃条件下处理5min后仍能保持30%左右的酶活。上述结果表明,与野生型相比,本发明提供的木聚糖酶突变体的耐热性得到显著提高。
综上所述,本发明提供的木聚糖酶突变体XynA1、XynA2和XynA3的最适作用温度为60℃,且比野生型木聚糖酶具有更强的耐热性,因此更适合广泛应用于饲料加工领域,前景广阔。
以上所述仅是本发明的优选实施方式,应当指出,对于本技术领域的普通技术人员来说,在不脱离本发明原理的前提下,还可以做出若干改进和润饰,这些改进和润饰也应视为本发明的保护范围。
SEQUENCELISTING
<110>青岛蔚蓝生物集团有限公司
<120>木聚糖酶突变体及其应用
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