The glucose concentration in thesupernatant was determined by using a glucose oxidase colorimet-ric analysis kit (TR-1511-200 Thermo Electron Noble Park, Victoria,Australia) and the factor 0.9 was used to convert anhydrous glu-cose released to the percentage starch hydrolysis. The residueafter repeated washing (×3) was dried under vacuum at 40◦C andobserved using scanning electron microscopy as described previ-ously