An Improved Enzyme Product for Low pH Liquefaction of Dry Milled Grain

The manufacturing of ethanol from cereal crop by enzymatic conversion of starch to fermentable glucose and fermentation by yeast is now a well established process. The first phase of the process is the addition of alpha-amylases to the liquefaction of the milled grains. Alpha-amylases hydrolyses the α-1,4-glucosidic bonds to reduce the viscosity of gelatinized starch producing soluble starch and oligosaccharides. Conventional alpha-amylases perform best at specific process conditions; the recommended pH is normally between 5.6-5.8, the recommended temperature 83-85°C. Deviations from the recommended conditions can result in inactivation of the enzyme. Other factors that have an impact on alpha-amylase performance are the presence of enough free calcium and the absence of inhibitors like phytic acid. Phytic acid (inositol 1,2,3,4,5,6-hexakis dihydrogen phosphate) present in wheat and corn complexes minerals like calcium and zinc and inactivates enzymes used to convert starch to fermentable glucose. Phytic acid can be hydrolysed by phytase, releasing free phosphate and inositol which cannot longer complex with calcium. Endogenous phytase is present in small grains (like wheat, barley), but not in corn and sorghum.