Optimization of Extracellular Keratinase Production by Aspergillus terreus Isolated from Chicken's Litter

In this current study 45 fungal isolates were isolated from chicken's litter on Feather Agar Medium (FAM) were screened for determining the potent keratinase producing isolates. Out of these fungal isolates, twelve species and one species variety exhibited various degrees of keratinolytic activities from which A. terreus showed the highest keratinase production (12.6U/ml). The optimum temperature and initial pH for keratinase production by A. terreus were 40°C and 8, respectively. The highest keratinase production was observed for a period 25 days. The optimum ionic strength for the enzyme production was 80mM NaCl. Deprivation of K+, Fe2+, Mg2+, Ca2+ or Zn2+ from the culture medium drastically reduced the keratinase production by A. terreus. In contrast, sulfur deprivation did not significantly affect the keratinase production. The Km and Vmax values for A. terreus keratinase were 8.64mg keratin and 56.7U/mg proteins, respectively. The optimum temperature, pH and ionic strength for keratinase activity were 35°C, 7.8 and 80-100mM NaCl, respectively.