EN
Optimizing production of α-amylase production by Thermoactinomyces vulgaris isolated from Egyptian soil was studied. The optimum incubation period, temperature and initial pH of medium for organism growth and enzyme yield were around 24 h, 55°C and 7.0, respectively. Maximum α-amylase activity was observed in a medium containing starch as carbon source. The other tested carbohydrates (cellulose, glucose, galactose, xylose, arabinose, lactose and maltose) inhibited the enzyme production. Adding tryptone as a nitrogen source exhibited a maximum activity of α-amylase. Bactopeptone and yeast extract gave also high activity comparing to the other nitrogen sources (NH₄Cl, NH₄NO₃, NaNO₃, KNO₃, CH₃CO2 NH₄). Electrophoresis profile of the produced two α-amylase isozymes indicated that the same pattern at about 135145 kDa under different conditions. The optimum pH and temperature of the enzyme activity were 8.0 and 60°C, respectively and enzyme was stable at 50°C over 6 hours. The enzyme was significantly inhibited by the addition of metal ions (Na⁺, Co²⁺ and Ca²⁺) whereas Cl⁻ seemed to act as activator. The enzyme was not affected by 0.1 mM EDTA while higher concentration (10 mM EDTA) totally inactivated the enzyme.