木聚糖酶Shearzyme 500 L对蔗渣木聚糖的特性研究

以木聚糖酶Shearzyme 500L水解蔗渣木聚糖制备低聚木糖，用DNS法测定酶解液中的总糖和还原糖，HPLC法测定酶解产物组成，其适宜的水解条件为底物质量浓度3g/100mL、pH5.0、60℃、木聚糖中酶用量50U/g、水解时间24h。在此条件下底物水解率约为63.1%，水解产物的81.5% 为低聚木糖，其中木二糖占54.8%，木三糖占26.7%。Shearzyme 500L 不能将一分子木二糖水解为两个木糖单糖，但能水解木三糖并相应生成木二糖与木糖。副产物木糖能显著抑制Shearzyme 500L 活性，降低木聚糖的水解率。

Enzymatic Hydrolysis Properties of Bagasse Xylan by Xylanase Shearzyme 500L

Xylanase Shearzyme 500L was used to hydrolyze bagasse xylan for preparing xylooligosaccharide. DNS was used to determine the contents of total sugar and reducing sugar in hydrolysates and HPLC was used to determine the compositions of hydrolysates. The optimal hydrolysis conditions were substrate concentration of 3 g/100 mL, hydrolysis pH of 5.0, hydrolysis temperature of 60 ℃, enzyme addition amount of 50 U/g and hydrolysis time of 24 h. Under the optimal hydrolysis conditions, the hydrolysis rate of bagasse xylan was approximately 63.1%, and the xylooligosaccharide in hydrolysates was up to 81.5%, which included 54.8% xylobiose and 26.7% xylotriose. Xylotriose could be hydrolyzed to xylobiose and xylose by xylanase shearzyme 500 L, but xylobiose could not be hydrolyzed to xyloses. The by-product xylose could also obviously suppress the activity of xylanase shearzyme 500 L and reduce the hydrolysis rate of bagasse xylan.