Abstract
General properties and the mode of action were investigated using the purified extracellular inulase (P-II) preparation from the culture filtrate of Aspergillus niger-12. Optimal pH and temperature of the enzyme reaction were 5.0 and 55°C, respectively. The enzyme was stable from pH 4 to 7 (30°C, 24 hr) and completely inactivated when heated for 30min at 80°C (pH 5.0). The enzyme was activated by divalent metal ions such as Mn2+, whereas markedly inactivated by Hg2+, Ag+, and PCMB. The enzyme catalyzed the hydrolysis of inulin, sucrose and raffinose by splitting off terminal fructosyl units, but not bacteria levan and melezitose. The enzyme seemed to act on inulin, liberating fructose from fructose end of inulin and producing one molecule of glucose finally. Therefore, this enzyme was considered to be an exo-inulase. The Km value for inulin was 1.87×10-3M.
