凝胶过滤色谱法研究酶解过程中木聚糖分子结构的变化

采用凝胶过滤色谱法研究了木聚糖在酶解过程中分子量分布的变化。结果表明,木聚糖酶对高分子量组分的木聚糖的降解能力较差,而主要降解分子量介于15000～3000之间组分的木聚糖,使得这部分木聚糖变为分子量更低的木聚糖组分。随着酶解时间的延长,酶解得率上升,酶解产物中低聚木糖含量增多,未被酶解的木聚糖的平均聚合度上升,当酶解时间超过4h时,这种变化趋势缓慢。随着酶解轮次的增加,酶解产物中可溶性木聚糖的含量越来越少,木聚糖被降解的难度越来越大。在实际生产中,用来作为低聚木糖生产的木聚糖其聚合度应在20～100之间,酶解时间以4h为宜,重复利用未水解木聚糖的轮次以2轮为宜。

The Changes in the Structure of Xylan during Enzymatic Hydrolysis with Gel Filtration Chromatography

The changes of the molecular weight distributions of xylan during enzymatic hydrolysis have been investigated with gel filtration chromatography. The results indicated that xylan of high molecular weight were difficult to be hydrolyzed by xylanase, and xylan of molecular weight between 15 000 and 3 000 were easy to be hydrolyzed and became xylan of lower molecular weight. Yield of xylo-oligosaccharides increased and average degree of polymerization of unhydrolyzed xylan increased with increasing of hydrolysis time, however, when hydrolysis time was more than 4 h, changes of yield of xylo-oligosaccharides and average degree of polymerization of unhydrolyzed xylan were slight. Xylan became more difficult to be hydrolyzed and dissoluble xylan of enzymatic hydrolysate was less with increasing of times of reuse. Practically, it was appropriate to use xylan of molecular weight between 15 000 and 3 000 as material to produce xylo-oligosaccharides and hydrolyze for 4 h and reuse the unhydrolyzed xylan for two times.