Abstract:

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.

Key words: Aspergillus ficuum, endoinulinase, optimizing enzymatic hydrolysis, kinetics