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

This work presents the purification and characterization of an extracellula r alpha-amylase (1,4-alpha-D-glucan glucanohydrolase, EC 3.2.1.1) produced by a new lactic acid bacterium: Lactobacillus manihotivorans able to produc e L(+) lactic acid from starch. The molecular weight was found to be 135 kD a. The temperature and pH optimum were 55 degrees C and 5.5, respectively, and pI was 3.8. The alpha-amylase had good stability at pH range from 5 to 6 and the enzyme was sensitive to temperature, losing activity within 1 h o f incubation at 55 degrees C. Higher thermal stability was observed when th e enzyme was incubated in presence of soluble starch, K-m value and activat ion energy were 3.44 mg/ml and 32.55 kJ/mol, respectively. Amylose was foun d to be a better substrate than soluble starch and amylopectin. Al3+, Fe3+, and Hg2+ (10 mM) almost completely inhibited the alpha-amylase. (C) 2000 E lsevier Science Inc. All rights reserved.