Extracellular inulinases from Penicillium janczewskii, a fungus isolated from the rhizosphere of Vernonia herbacea (Asteraceae)

Extracellular inulinases from Penicillium janczewskii were obtained from the filtrate of 12 day‐old cultures supplemented with inulin from Vernonia herbacea. Crude filtrates and partially‐purified enzyme preparations (peaks I and II) were active on inulin, sucrose and raffinose. The apparent Mr of the enzymes from peaks I and II were 48 and 66 kDa, respectively. The apparent Km (mmol l−1) values of peak I were 0·43 for inulin and 18·7 for sucrose; for peak II they were 0·87 and 18·5 for inulin and sucrose, respectively. Their temperature and pH optima were 55 °C and 5·0, respectively. Both peaks catalysed the hydrolysis of β‐(2,1) fructans more rapidly than β‐(2,6) fructans. Free fructose was the predominant product released from inulin, indicating that these enzymes display exo‐inulinase activity. In view of these characteristics, the yield and the high specific activity towards β‐(2,1) fructans, inulinases from P. janczewskii can be utilized for the preparation of fructose syrup from inulin.