Production and optimization of extracellular α-amylase productivity from Bacillus subtilis

A moderately thermophilic strain of Bacillus subtilis was isolated from agricultural soil at the National Root Crops Research Institute (NRCRI), Umudike, Umuahia, Nigeria. The organism produced a thermostable α-amylase in complex medium containing 2% (w/v) soluble starch. Peak amylase activity was obtained at 48 h of fermentation period which corresponded with the late exponential phase of the organism. Amylase activity was more strongly expressed with corn than soluble starch. Optimized medium containing 1.5% (w/v) corn starch increased amylase production to 6427±168 U/L against 4168±132 U/L obtained in the basal medium containing 2% (w/v) corn starch. The optimum temperature and pH of the enzyme were 65°C and 6.5 respectively.