الفهرس 
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Abstract
A number of 75 actinomycete strains and 18 fungal species were isolated from soil, compost, animal and poultry farms in Damietta Governorate. The eighteen fungal species were identified namely; Aspergillus niger, A. terreus, A. flavus, A. restrectus. A. parasiticus, A. versicolor. A. glaucus, A. ochraceus, Penicillium nigricans, P. chrysogenum, Scopulariopsis sp., Chrysosporium keratinophillum. Fusarium oxysporum, Trichophyton mentagrophytes, Trichoderma sp. Alternaria sp., Syncephalastrum sp. and Absidia corymbifera. These isolates were screened for their keratinase production abilities. A strain of actinomycetes identified as FM 13 Streptomyces themroflavus and one fungal species identified as Trichophyton mentagrophytes var. quinckeanum proved to be the highest keratinolytic producers than the other tested isolates. The optimum conditions for keratinase biosynthesis by these two microorganisms were studied. The results reported herein revealed that, the optimum temperature for Streptomycetes thermoflavus growth and keratinase production was 55oC but was 40oC for Trichophyton mentagrophytes. The maximum production of keratinases were recorded at 5 days for Streptomycetes thermoflavus and at 30 days for Trichophyton mentagrophytes. Moreover, the maximal production of keratinases were recorded at pH 8.5 and 8.0 for Streptomycetes thermoflavus and Trichophyton mentagrophytes respectively. The best carbon sources stimulating the keratinases production were starch and mannose for Streptomycetes thermoflavus and Trichophyton mentagrophytes respectively. The optimization of keratinases activity using crude enzyme preparation revealed that, the optimum temperatures were 55oC and 35oC for both Streptomycetes thermoflavus and Trichophyton mentagrophytes respectively. However, the maximal productivities were recorded at pH 8.5 & 8.0 for Streptomycetes thermoflavus and Trichophyton mentagrophytes respectively. SDSPAGE revealed that the keratinase enzyme produced by Streptomycetes thermoflavus was obtained as a monomeric enzyme protein with a molecular weight of about 45 kDa, and the keratinase of Trichophyton mentagrophytes with a molecular weight of about 52 kDa.