ScienceAsia 23 (1997): 199-208 |doi: 10.2306/scienceasia1513-1874.1997.23.199

PURIFICATION AND CHARACTERIZATION OF GLUCOAMYLASE FROM A RHIZOPUS ORYZAE MUTANT

W. SUNTORNSUK^a AND Y.D. HANG^b

ABSTRACT: Glucoamylase produced by Rhizopus oryzae mutant 4U2 was purified nearly 3-fold with a yield of 15% by ammonium sulfate fractionation, Sephadex G-100 gel filtration, CM-Sephadex chromatography, and chromatofocusing. The purified enzyme was most active at pH 4.0 and showed a temperature optimum at 55^oC. The enzyme was stable for an hour at temperatures up to 400C and over a pH range of 3.0 to 7.0. It had an isoelectric point (pI) of 8.2 and its molecular weight was approximately 80 kDa as determined by gel filtration on Sephadex G-100 and SDS-PAGE. The K_m of the enzyme for amylopectin and soluble starch were 2.4 and 12.2 mg/mL, respectively. The Vmax for amylopectin and soluble starch were 2.3 and 5.0 mM glucose per mg protein per min, respectively.

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a Department of Microbiology, Faculty of Science, King Mongkut's Institute of Technology Thonburi, Rasburana, Bangkok 10140 Thailand.
b Department of Food Science and Technology, Cornell University, Geneva, NY 14456 USA.

Received 17 FEBRUARY, 1997