Mode of alpha-amylase production by the shochu koji mold Aspergillus kawachii
2003
Nagamine, K. (National Research Inst. of Brewing, Higashihiroshima, Hiroshima (Japan)) | Murashima, K. | Kato, T. | Shimoi, H. | Ito, K.
Aspergillus kawachii produces two kinds of a-amylase, one is an acid-unstable a-amylase and the other is an acid-stable a-amylase. Because the quality of the shochu depends strongly on the activities of the a-amylases, the culture conditions under which these a-amylases are produced were examined. In liquid culture, acid-unstable a-amylase was produced abundantly, but, acid-stable a-amylase was not produced. The acidunstable a-amylase was produced significantly when glycerol or glucose was used as a carbon source, similarly to the use of inducers such as starch or maltose. In liquid culture, A. kawachii assimilated starch at pH 3.0, but no a-amylase activity was recognized .in the medium. Instead, the a-amylase was found to be trapped in the cell wall. The trapped form was identified as acid-unstable a-amylase. Usually, acid-unstable a-amylase is unstable at pH 3.0, so its stability appeared to be due to its immobilization in the cell wall. In solid-state culture, both kinds of a-amylase were produced. The production of acid-stable a-amylase seems to be solid-state culture-specific. and was affected by the moisture content in the solid medium.
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