The Liquefying Action of Pancreatic, Cereal, Fungal, and Bacterial Alpha‐Amylases a

SUMMARY The starch‐liquefying abilities of alpha‐amylases from pancreas, cereals, fungi, and bacteria were studied by following changes in the viscosity of potato starch pregelatinized and cooled in the Amylograph under standardized conditions and acted on by the enzyme at 37°C. The optimal pH activity for starch liquefaction was 4.0 for fungal, 4.5 for cereal, 6.5 for bacterial, and 7.0 for pancreatic amylase. A comparison of liquefying action of the enzyme systems at a constant level of dextrinogenic activity showed the pancreatic enzyme most active, followed by cereal, with the fungal least active. The relative differences between the activity of the bacterial and fungal enzymes at their optimum pH's and at 37° depended on the levels of enzyme added. The thermostable bacterial amylase also exhibited high stability toward high acidity. The pattern of starch liquefaction by action of the various enzymes, and the relation between viscosity drop and enzyme activity, are discussed.