Purification and Characterization of Extracellular Inulinase from a Marine Yeast Pichia guilliermondii and Inulin Hydrolysis by the Purified Inulinase

The extracellular inulinase of the marine yeast Pichia guilliermondii strain 1 was purified to homogeneity resulting in a 7.2-fold increase in specific inulinase activity. The molecular mass of the purified enzyme was estimated to be 50.0 kDa. The optimal pH and temperature for the purified enzyme were 6.0 and 60 degrees C, respectively. The enzyme was activated by Mn2+, Ca2+, K+, Li+, Na+, Fe3+, Fe2+, CU2+, and Co2+, but Mg2+, Hg2+, and Ag+ inhibited activity. The enzyme was strongly inhibited by phenylmethanesulphonyl fluoride (PMSF), iodoacetic acid, EDTA, and 1, 10-phenanthroline. The K-m and V-max values of the purified inulinase for inulin were 21.1 mg/mL and 0.08 mg/min, respectively. A large number of monosaccharides were detected after the hydrolysis of inulin. The deduced protein sequence from the cloned P. guilliermondii strain 1 inulinase gene contained the consensus motifs R-D-P-K-V-F-W-H and W-M-N-D-P-N-G, which are conserved among the inulinases from other microorganisms. (C) KSBB