Optimization of keratinase production by keratinolytic fungus Chrysosporium tropicum and its potentiality in bidegradation of chicken feathers

Abstract

The current study has been designed to investigate the possible biodegradtion of native keratin by fungi isolated from chicken feathers collected from chicken farms in Egypt. Out of 56 fungal isolates 23 species and 2 species varieties showed different degrees of keratinolytic activity, with Chrysosporium tropicum showing the highest keratinase productivity (23.15 U/ml) as well as the highest value of specific activity for keratinase (197.90 U/mg protein) indicating a great degree of purity for the enzyme. Our present study indicates that the highest production of keratinase by C. tropicum was recorded at pH 8 and a temperature of 35 °C during a period of 20 days. In addition the optimal value of ionic strength for keratinase production was 100 mM NaCl. Monitoring the influence of constituents deprivation from basal salt medium on production of keratinase enzyme showed that K+, Fe2+, Mg2+, Ca2+ and Zn2+ were necessary for keratinase production. Sulfur deprivation has no significant influence on keratinase production. Keratinase activity of C. tropicum showed that, the optimal values of temperature and ionic strength were 35–40 °C and 80 mM NaCl, individually. The optimum pH range was (7.8–9). These promising findings demonstrate a high potentiality of C. tropicum keratinase in keratin proteolysis, suggesting that keratinase producing isolates of C. tropicum may be suitable as a biodegradation agent.