Screening and identification of a novel rawstarch-digesting glucoamylase producing strain Absidia and its enzymatic property

Abstract:

A novel strain which could produce raw starch-digesting glucoamylase was isolated from Baoning bran vinegar Daqu and numbered as CQB43. Its raw starch-digesting glucoamylase activity was 105.2 U/mL and the RDA value was 27.9%. The species attribution of the strain was confirmed to be Absidia corymbifera by the characterization of morphological, and the similarity of the nucleotide sequence of the 26S rDNA gene and ITS region gene of the strain. Then the enzyme characters of the crude extracts produced by Absidia corymbifera CQB43 were studied. The optimum pH for the enzyme activity was 5.0, and it was very stable at the the pH range about 4.0-5.6. The optimum temperatures was 40 °C. Besides, the enzyme was very stable at the temperature of less than 60 °C, as its remnant activities was about 88% after 2 hours at 60 °C. According to the research on enzyme activity affected by metallic ion, it was activated by Co2+, whereas the activity was inhibited by Fe3+ and Ca2+.