Starch is a high yield feedstock for ethanol production, but its hydrolysis is required to produce ethanol by fermentation. Starch was traditionally hydrolyzed by acids, but the specificity of the enzymes, their inherent mild reaction conditions and the absence of secondary reactions have made the amylases to be the catalysts generally used for this process. Alpha-amylase obtained from thermo-resistant bacteria like Bacillus licheniformis, engineered strains of Escherichia coli or Bacillus subtilis is used during the first step of hydrolysis of starch suspensions. For amylases to attack starch, these suspensions should be brought to high temperatures (90–110 °C) for the breakdown of starch kernels. Apar and Ozbek (2004) provide information about the effects of operating conditions on the enzymatic hydrolysis of corn starch using commercial α-amylase.