Production, purification, and characterization of alpha-amylase by Bacillus subtilis and its mutant derivates

Abstract

The effects of various carbon and nitrogen sources on production of alpha-amylase by Bacillus subtilis and its mutant derivates were investigated. The maximum production of alpha-amylase by all strains was obtained in the presence of mesoinositol as the carbon source. There was no more significant 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. alpha-Amylases of B. subtilis and its mutant strain (EBUE 5-3) were purified through a series of steps, and characterized. The optimum temperature and pH values of the purified amylases were found to be 45 degrees C and 6.0, respectively. The 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). The K-m and V-max 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 effect on enzyme activities than 5 mM did. The estimated molecular weight of the purified enzymes was 56 kDa. The N-terminal amino acid sequence of amylases produced by the parental and the mutant strain showed homology.