Optimum Production and Characterization of Thermostable Amylolytic Enzymes from B. stearothermophilus GRE1

Abstract

Optimum production of extracellular, thermostable amylolytic enzymes (α and β‐amylase) by a newly isolated bacterium, Bacillus stearothermophilus, was investigated in a batch bioreactor. Starch and lactose at 1.0% and 3.0% (w/v) respectively were found to be optimum for maximum enzyme production. Optimization of cultural conditions (pH 7.0 and temperature 45°C) resulted in high bacterial specific growth rate (0.64 h−1), yielding 2.20 gL−1 biomass, 11.43 UmL−1 α‐amylase and 10.04 UmL−1 of β‐amylase. Hydrolysis of native starches from wheat, cassava, corn and potato at 60°C using the crude enzyme showed 60‐80% saccharification with potato starch showing the least and wheat starch showing the greatest hydrolysis. The Km and Vmax values of the crude α‐amylase for starch were 4.78 mg starch/mL and 6.67 mg/mL.min respectively.

High‐Solids Bio‐Conversion of Maize Starch to Sugars and Ethanol

“…Enzyme‐catalyzed hydrolysis offers substantial advantages over acid hydrolysis. The specificity of amylolytic enzymes and their use under mild reaction condition allow the production of sugars in very high yield from starch …”

Amylase production under solid state fermentation by a bacterial isolate W74

“…Enzymatic hydrolysis of starch is carried out under temperatures up to 100°C, normal pressure, and pH of medium around 6.0 to 8.0. However, enzymes are relatively expensive and above all thermally unstable at higher temperatures as reviewed in Hossain et al (2006). Attempts are now being made to find enzymes from thermophilic microorganisms.…”