Biography
Biography: Ayalew Damte
Abstract
Bacillus sp. LCBC245, which grew at a temperature of 30 0C, pH of 10.3 and under anaerobic condition, produced an alkaline amylase. The growth of the organism and amylase production reached a maximum of 0.46 and 74.09U/ml, respectively, after 36 h of incubation. The organism secreted a maximum of 69.12 and 76.96 (U/ml) of amylase when grown in liquid media containing (w/v) 1% maize and 0.5% peptone as the sole carbon and nitrogen source, respectively. On the other hand, the level of enzyme production reached a peak value of 59.52 U/ml at 0.1M NaCl and 34.23U/ml at 1% of raw starch and thereafter progressively declined in both cases. The enzyme performed optimally in the range 55-65 0C, with a peak value of 100%, and 50-600C, with a peak value of 77.59%, in the presence and absence of 5mM CaCl2, respectively. LCBC245 amylase lost more than 70 % of its activity for NaCl concentrations exceeding 1M at incubation temperature of 50 0C for 15min and in the presence of 5mM CaCl2. After the enzyme was incubated at 55 0C for 1 h it retained 66.91% and 61.42% of its original activity corresponding to the presence and absence of 5mM CaCl2 in the reaction mixture. The optimum pH of the enzyme was 10.5 and it was stable in broad pH ranges (8-11). It had a relative residual activity of 86.33 after it was incubated for 1 h at pH 11 in 50 mM Glycine-NaOH buffer. As far as its reducing power is concerned LCBC245 amylase was able to liberate 504.25μmol/ml of reducing sugar equivalents by hydrolyzing 36.31% of a previously gelatinized starch [25 % (w/v)] after 10 h of incubation at 60 0C and pH of 10. Thus, the amylase from LCBC245 is a liquefying type. Therefore, the amylase from Bacillus sp., LCBC245 was stable at high alkaline pH ranges and required Ca+2 for enhancing its thermoactivity and thermostability. The organism produced amylase maximally when grown in media containing undefined carbon sources, 0 M NaCl and organic nitrogen sources, and incubated under anaerobic condition.