Keratinolytic Activity of Aspergillus fumigatus Fresenius |
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Authors: | Regina MDB Santos Alexandre AP Firmino Cezar M de Sá Carlos R Felix |
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Institution: | (1) Departamento de Biologia Celular, 70.910-900 Universidade de Brasília, DF, Brasil , BR |
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Abstract: | Aspergillus fumigatus can utilize chicken feather keratin as its sole carbon and nitrogen source. Because enzymatic conversion of native keratin
into readily usable products is of economic interest, this fungus was studied for its capacity to produce and secrete keratin-hydrolyzing
proteinases. Substantial keratin-azure hydrolyzing activity was present in the culture fluid of keratin-containing media.
Considerably lower activity was present in cultures containing glucose and nitrate as the carbon and nitrogen sources, or
keratin plus glucose and nitrate. Secretion of keratin-hydrolyzing activity in A. fumigatus was induced by keratin but repressed by low-molecular-weight carbon and nitrogen sources. The amount of keratinolytic enzyme
present in the culture fluid was dependent on the initial pH of the culture medium. The crude enzyme also hydrolyzed native
keratin and casein in vitro. Hydrolysis was optimal at pH 9 and 45°C. The crude enzyme was remarkably thermostable. At 70°C,
it retained about 90% of its original activity for 1.5 h. The obtained results indicated that the A. fumigatus keratinolytic enzyme may be suitable for enzymatic improvement of feather meal.
Received: 25 April 1996 / Accepted: 18 June 1996 |
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