Purification and characterization of two isoforms of exoinulinase from Penicillium oxalicum BGPUP-4 for the preparation of high fructose syrup from inulin.

Two exoinulinases, Exo-I and Exo-II from the culture broth of Penicillium oxalicum BGPUP-4 was purified using three-step purification method i.e., isopropanol precipitation, Q-Sepharose and Sephadex G-100 column chromatography. The molecular weight of Exo-I and Exo-II was determined to be 64.85 kDa and 32.54 kDa, respectively using MALDI-TOF. Exo-I and Exo-II showed high specificity for inulin and their respective V/K ratio was 3.74 and 7.20. Besides, both the inulinases also displayed specificity for lactose, sucrose and raffinose. Exo-I and Exo-II were stable at a pH range of 4.0-8.0 with pH optima 5.0. Optimal temperature for both the inulinases was 55 °C, and both the isoforms retained approximately 50% of their activity up to 70 °C. Ag, Hg, Ba, Cu and Ca ions shown stimulatory effect on inulinases activity, while Fe, Mn, Coand EDTA completely inhibited enzyme activity. Purified enzyme was successfully used for the preparation of high fructose syrup from inulin.