Partial purification and some properties of alpha-amylase and Glucoamylase obtained as by-product from direct fermentation of Sago starch to solvent by Clostridium acetobutylicum

The starch degrading enzymes, alpha-amylase and glucoamylase, obtained from direct fermentation of sago starch to solvent by C. acetobuylicum P262 were partially purified and some of the biochemical characteristics were identified. The alpha-amylase was found to have maximum activity at pH 5.3 and was stable in a pH range from 3 to 9. The optimum temperature for alpha- amylase activity was 40 Centigrade and only 50 % of its original activity was retained after incubation for 1 h at 60 Centigrade. The alpha-amylase Km and Vmax values for soluble starch was 0.31 g/L and 10.03 U/mL, respectively. Hydrolysis rate of partially purified alpha-amylase was illustrated by the relative values of starch (100%), amylopectin (68%) and amylose (42%). The optimum pH and temperature for glucoamylase was 4.4 and 40 Centigrade, respectively. Glucoamylase was stable at a wide pH range (4-8). The enzyme was also stable at high temperatures where 80% of its activity was retained after 1 h incubation at 60 Centigrade. Glucoamylase has high affinity towards soluble starch (Km = 0.039 g/L), followed by maltose (Km = 4.39 g/L) and maltotriose (Km = 10.43 g/L).