الفهرس 
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Abstract
The present investigation is an attempt to study the ability of some Bacterial isolates to degrade keratin of white chicken feathers, to be used as a digestable dietary medium source for animal feed. Such study is also of ecological significance to reduce pollution problems. The aim of the study was to characterize keratinolytic bacteria isolated from feather wastes and study the keratinase enzyme, which is produced by the degrading organisms as possible bases for potential biotechnological use in several applications in industry involving keratin hydrolysis.
The experimental results could be summarized as follows:
(1) Twenty two rod shaped, gram-positive and endospore-forming bacteria were isolated from chicken feather wastes.
(2) The rod shaped bacteria were classified belong to the genus Bacillus and were distinguished into 5 related groups
1) B. licheniformis which included seven isolates (No. 1, 2, 3, 10, 11, 13 and 16).
(2) B. coagulans which included five isolates (No. 5, 9, 18, 21 and 22).
(3) B. pumilus which included two isolates (No. 6 and 20).
(4) B. megaterium which included four isolates (No. 4, 7, 8 and 17).
(5) B. subtilis which included four isolates (No. 12, 14, 15, and 19).
(3) Screening of the keratinolytic activity of the22 different Bacillus spp. on solid mineral medium amended with Ks or in liquid mineral medium amended with defatted white chicken feathers or in skim milk medium (solid medium) indicated that Bacillus licheniformis isolates No. (3 and 16) were the most active in keratin degradation so they were selected for further experimentations.
(4) Optimum incubation period, pH and temperature for white chicken feather degradation and keratinase production by Bacillus licheniformis isolates No. (3 and 16) were 3 days, pH 8 and 45oC, respectively.
(5) Bacillus licheniformis isolates No. (3 and 16) recorded high keratinase, soluble protein and ammonia production at 1% feather concentration.
(6) Growth of Bacillus licheniformis isolates No. (3 and 16) on media with different combination of 1% glucose, 30 mM NH4Cl and 0.05% MgSO4 indicated that 1% glucose stimulated production of keratinase whereas NH4Cl had inhibitory effect. MgSO4 stimulated keratinase production slightly.
(7) The keratinase enzyme is inducible and is produced only in the presence of keratin.
(8) Keratin from white chicken feather was more favourable for keratinase production by Bacillus licheniformis isolates No. (3 and 16) than black and white duck feather, cow hair, human hair, sheep wool.
(9) Alginate immobilized Bacillus licheniformis isolates No.3 recorded high keratinase production by the organism for two runs.
(10) 2-3% alginate concentration, large surface area and addition of keratin powder as adjuvant were optimum for the enzyme activity in the immobilization process.
(11) pH 8 was optimum for keratinase activity by immobilized keratinase enzyme.
(12) At pH 4, 7 and 10, keratinase was stable for 2 hours and retained 55.5%, 60% and 53%, of its activity respectively for immobilized enzyme while free enzyme retained only 40%, 40% and 61%.
(13) Optimum temperature for keratinase activity was 50 oC when immobilized in alginate.
(14) At temperatures 30, 45 and 60 oC, keratinase was stable for 2 hours and retained 57%, 66% and 57%, of its activity respectively for immobilized enzyme while free enzyme retained only 51%, 62% and 51%, respectively.
(15) Addition of NaCl (5, 10, 15 mM), EDTA, MgSO4 and ZnSO4 stimulated the activity of free keratinase while NiCl2, Urea, HgCl2, NaN3. and KCl had inhibitory effect of keratinase.
(16) The addition of NiCl2, Urea, HgCl2, NaN3 and KCl showed partial inhibition effect on immobilized keratinase when compared with the free one.