| 摘要 |
Heat and acid-stable alpha-amylase enzymes having the following characteristics: (1) capable of retaining at least about 70% of their initial activity when held at 90.degree.C and at a pH of 6.0 for 10 minutes in the absence of calcium ion; (2) capable of retaining at least about 50% of their initial activity when held at 90.degree.C at a pH of 6.0 for 60 minutes in the absence of added calcium ion; (3) capable of retaining at least about 50% of their initial activity at a temperature of 80.degree.C and at a pH of 4.55 in the presence of 5mM calcium ion for 10 minutes; and/or (4) capable of retaining at least about 95% of their initial activity at a temperature of 80.degree.C at a pH ranging from about 4 to about 6.5. The preferred alpha-amylases are prepared by culturing a strain of a Bacillus stearothermophilus microorganism in a suitable culture medium. The novel alpha-amylases are useful in hydrolyzing and/or liquefying starch and due to their stability at low pH values they can be used in conjunction with other acid stable amylases such as glucoamylase in either a soluble or an immobilized form. |
