PURIFICATION AND CHARACTERIZATION OF A THERMOSTABLE α-GALACTOSIDASE FROM THIELAVIA TERRESTRIS NRRL 8126 IN SOLID STATE FERMENTATION

Several seeds and husks of some plants belonging to leguminosae, Graminae, Compositae and Palmae were evaluated as carbon substrates to produce alpha-galactosidase (alpha-Gal) by the thermophilic fungus, Thielavia terrestris NRRL 8126 in solid substrate fermentation. The results showed that Cicer arietinum (chick pea seed) was the best substrate for alpha-Gal production. The crude enzyme was precipitated by ammonium sulphate (60%) and purified by gel filtration on sephadex G-(100) followed by ion exchange chromatography on DEAE-Cellulose. The final purification fold of the enzyme was 30.42. The temperature and pH optima of purified alpha-Gal from Thielavia terrestris were 70 degrees C and 6.5, respectively. The enzyme showed high thermal stability at 70 degrees C and 75 degrees C and the half-life of the alpha-Gal at 90 degrees C was 45 min. K-m of the purified enzyme was 1.31 mM. The purified enzyme was inhibited by Ag2+, Hg2+, Zn2+, Ba2+, Mg2+, Mn2+ and Fe2+ at 5 mM and 10 mM. Also, EDTA, sodium arsenate, L-cysteine and iodoacetate inhibited the enzyme activity. On the other hand, Ca2+, Cu2+, K+ and Na+ slightly enhanced the enzyme activity at 5 mM while at 10 mM they caused inhibition. The molecular weight of the alpha-Gal was estimated to be 82 kDa by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. This enzyme displays a number of biochemical properties that make it a potentially strong candidate for biotechnological and medicinal applications.