Production of inulooligosaccharides by endoinulinases from Aspergillus ficuum

Inulooligosaccharide (IOS) production from inulin was studied using a partially purified endoinulinase and a purified endoinulinase, which originated from Aspergillus ficuum. At the optimal conditions, including 50 g/L inulin, an enzyme concentration of 10 U/g substrate, 45 °C, and pH 6.0, the inulin-degrading degree by partially purified endoinulinase was 74% and an IOS yield over 50% were observed after 72 h. The major products were identified as DP2 to DP4. The purified Endo-I was used for inulo-oligosaccharide production at the optimal conditions obtained with orthogonal experiments, including pH 5.0, 45 °C, 50 g/L inulin, and an enzyme concentration of 10 U/g substrate. With pure inulin as substrate, the maximum inulin-hydrolyzing degree was 75% and the total IOS yield was 70% after 72 h. The hydrolysis products consisted of DP2 to DP8 with HPLC, and DP3 and DP4 were relatively high. With Jerusalem artichoke juice as substrate, the inulin-hydrolyzing extent reached 89% and the maximum IOS production was up to 80% after 72 h. Various IOS with different DP (mainly DP2, DP3, DP4, DP5, DP7, DP8) were evenly distributed in the final reaction products.