Aspergillus ficuum 内切菊粉酶的酶解条件优化及酶解动力学研究

采用Aspergillus ficuum 内切型菊粉酶Endo-Ⅰ 酶解商品菊粉制备低聚果糖，经正交试验确定其最适酶解条件为：pH5.0、温度45℃、底物浓度50g/L、加酶量10U/g，在此酶解条件下，低聚果糖得率可达70.37%，酶解产物以DP3 和DP4 为主，同时含有一定量的DP2、DP5、DP6、DP7、DP8；在此条件下酶解自制菊芋干粉时，低聚果糖得率为41.72%，酶解产物以DP3～DP6 的低聚果糖为主，DP2 含量很少，同时酶解液中还含有大量的果糖；在此条件下酶解自制菊芋提取液时，低聚果糖得率高达79.80%，酶解产物中除DP6 含量较低外，其他各聚合度的低聚糖分布比较平均。在此相同酶解条件下酶解72h 时，3 种底物中，以菊芋提取液酶解后的低聚果糖得率最高。因此，应用Aspergillus ficuum 内切型菊粉酶Endo-Ⅰ酶解菊芋制备低聚果糖宜选择菊芋提取液作底物。

Optimization and Kinetics of Enzymatic Hydrolysis of Aspergillus ficuum Endoinulinase

Purified endoinulinase from Aspergillus ficuum was used for inulo-oligosaccharides production at the optimal condition obtained with orthogonal experiments, including pH 5.0, 45 ℃, 50 g/L inulin, and enzyme concentration of 10 U/g substrate. With pure inulin as substrate, the inulin-hydrolyzing degree was up to 75% and the total inulo-oligosaccharides yield was 70.37% after 72 h. The hydrolysis products consisted of DP2 to DP8 determined by HPLC, DP3 and DP4 exhibited a relatively high content. With Jerusalem artichoke powder as substrate, the inulin-degrading extent was 62.38% and the inulooligosaccharides yield was 41.72% after 72 h. DP3 to DP6 were liberated as the main products with a great amount of fructose in the reaction mixtures. With Jerusalem artichoke juice as substrate, the inulin-hydrolyzing extent reached 89% and the maximum inulo-oligosaccharides production was up to 79.80% after 72 h. Various inulo-oligosaccharides with different DPs (mainly DP2, DP3, DP4, DP5, DP7, DP8) were evenly distributed in final reaction products. Therefore, the juice was the most suitable for inulo-oligosaccharides production by A. ficuum endo-inulinase.