Aspergillus flavus produced approximately 50 U/mL of amylolytic activity when grown in liquid medium with raw low-grade tapioca starch as substrate. Electrophoretic analysis of the culture filtrate showed the presence of only one amylolytic enzyme, identified as an alpha-amylase as evidenced by (i) rapid loss of color in iodine-stained starch and (ii) production of a mixture of glucose, maltose, maltotriose and maltotetraose as starch digestion products. The enzyme was purified by ammonium sulfate precipitation and ion-exchange chromatography and was found to be homogeneous on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. The purified enzyme had a molar mass of 52.5 +/- 2.5 kDa with an isoelectric point at pH 3.5. The enzyme was found to have maximum activity at pH 6.0 and was stable in a pH range from 5.0 to 8.5. The optimum temperature for the enzyme was 55 degrees C and it was stable for 1 h up to 50 degrees C. The Km and V for gelatinized tapioca starch were 0.5 g/L and 108.67 mumol reducing sugars per mg protein per min, respectively.

School of Biological Sciences Universiti Sains Malaysia Penang

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Nature. 1970 Aug 15;227(5259):680-5 PubMed

J Biol Chem. 1952 Mar;195(1):19-23 PubMed

Arch Biochem Biophys. 1963 Mar;100:451-67 PubMed

Anal Biochem. 1984 Nov 1;142(2):421-36 PubMed

Arch Biochem Biophys. 1955 Jan;54(1):154-61 PubMed

Appl Environ Microbiol. 1977 Jul;34(1):1-6 PubMed

Arch Biochem Biophys. 1969 Nov;134(2):539-53 PubMed

Biochem J. 1988 Mar 15;250(3):813-8 PubMed

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