Purification and characterization of an extracellular α-amylase produced by Lactobacillus manihotivorans LMG 18010T, an amylolytic lactic acid bacterium

This work presents the purification and characterization of an extracellular α-amylase (1,4-α-d-glucan glucanohydrolase, EC 3.2.1.1) produced by a new lactic acid bacterium: Lactobacillus manihotivorans able to produce L(+) lactic acid from starch. The molecular weight was found to be 135 kDa. The temperature and pH optimum were 55°C and 5.5, respectively, and pI was 3.8. The α-amylase had good stability at pH range from 5 to 6 and the enzyme was sensitive to temperature, losing activity within 1 h of incubation at 55°C. Higher thermal stability was observed when the enzyme was incubated in presence of soluble starch. Km value and activation energy were 3.44 mg/ml and 32.55 kJ/mol, respectively. Amylose was found to be a better substrate than soluble starch and amylopectin. Al3+, Fe3+, and Hg2+ (10 mM) almost completely inhibited the α-amylase.