Investigation on the activity of purified inulinase enzymes from fungal strains on the inulin extracted from chicory (Cichorium intybus) for production of fructose sweetener

Chicory is a rich plant source for the prebiotic inulin. The aim of this study was to evaluate the activity of purified inulinase enzyme from fungal strains on the inulin extracted from chicory. Inulin was extracted by soaking in water and precipitating in ethanol. Fungi were isolated from the soil around chicory root and screened for inulinase production along with fungal strains, Kluyveromyces marxianus PTCC ۵۰۰۶ and Aspergillus flavus PTCC ۵۳۰۴. The high inulinase-producing fungal isolate was identified based on the sequencing of ۱۸S rRNA gene. The enzyme was purified using ammonium sulfate-polyacrylamide and dialysis. The molecular weight of the protein was detected using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). One fungal isolate that showed high enzymatic activity (۲۲۳۳ U/ml) was obtained. This isolate was identified as the species Talaromyces moniliformis. Among the collection strains, Kluyveromyces marxianus had the highest inulinase production; while its inulinase activity was lower than that of Talaromyces moniliformis. The results from enzyme purification from Talaromyces moniliformis showed that the most specific enzyme activity (۵۴۶.۶ U/mg) and the highest purification yield (۶۲.۱۷%) were obtained by the precipitation in ۵۵% ammonium sulfate. Dialysis of the protein resulted in the extraction of a protein with a reduced specific enzyme activity (۱۸۸.۶ U/mg). The molecular weight of the purified protein was estimated at۱۵ kDa.The fungal inulinase which purified from native resources in the present study can be used in food and pharmaceutical industries due to its high enzymatic activity.

Keywords:

Inulin , chicory , Inulinase , Fungal strains , Enzyme purification