Production, purifi cation, and characterization of α-amylase by Bacillus subtilis and its mutant derivates

Th e eff ects of various carbon and nitrogen sources on production of α-amylase by Bacillus subtilis and its mutant derivates were investigated. Th e maximum production of α-amylase by all strains was obtained in the presence of mesoinositol as the carbon source. Th ere was no more signifi cant increase in enzyme yield in the case of the supplementation of nitrogen sources, whereas malt extract and tryptone were preferred nitrogen sources for amylase production by Bacillus subtilis and mutant U 2-6 strain, respectively. α-Amylases of B. subtilis and its mutant strain (EBUE 5-3) were purifi ed through a series of steps, and characterized. Th e optimum temperature and pH values of the purifi ed amylases were found to be 45 °C and 6.0, respectively. Th e enzyme of mutant strain had more stability than the enzyme of the parental strain in alkaline conditions (85% at pH 8.0 for 1 h). Th e Km and Vmax values of both amylases were also compared. Enzymes were strongly inhibited by Cu2+, Hg2+, and Ag2+, but activated by Ca2+, Ba2+, Mg2+, Li2+, and Mn2+. Metal ion concentration of 1 mM had a greater eff ect on enzyme activities than 5 mM did. Th e estimated molecular weight of the purifi ed enzymes was 56 kDa. Th e N-terminal amino acid sequence of amylases produced by the parental and the mutant strain showed homology.