الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Every year more than 20 000 tons of feathers are produced as waste by poultry
fanning (I). Poultry feathers accumulate in nature after processing of chicken for human
consumption creating a serious disposal problem leading to environmental pollution (I.
2). Feather is composed of over 90 % protein; its main component is keratin, an insoluble
highly cross-linked fibrous protein. Keratin is characterized by its high mechanical
stability and resistance to common proteolytic enzymes (2.3.4). Considering its high protein
content, this keratinous waste could have a great potential as a source of protein and amino
acids for animal feed and for many other applications. However, because of its insoluble
nature, use of feather keratin as a source of value-added products has been very limited.
Current commercial production of feather meal involves treatment at elevated
temperatures and high pressure, this energy intensive process, results in the loss of some
essential amino acids (2). Despite these features; a number of keratinolytic microorganisms,
mostly bacteria and fungi, have been reported. Keratinases of these microorganisms may
be useful in the biotechnological clean up of keratin-containing wastes such as feather,
thereby improving the nutritional value of feather meal (5). Furthermore, keratinases could
be applied for waste treatment, textile, medicine, cosmetic, leather, feed and poultry
processing industry (2.5.6).
Several Bacillus strains were isolated and identified for their ability to degrade
chicken feather. Strains belonged to Bacillus pumilus, B. cereus, and B. subtilis (7).
Moreover, several B. subtilis host strains were constructed by introducing the multicopy
plasmid (pS I) that carries the complete alkaline protease (apr£) gene, to enhance the
production of alkaline protease enzyme. The recombinant B. subtilis DB 100 (pS I) strain is
one of these constructed strains. This strain was found to be able to degrade 1 % chicken
feather in basal medium in almost 3 to 4 days. High level of keratinolytic activity was
obtained in the culture as determined by the level of NH2 free amino groups resulted.
Additionally, the physical appearance of feather was evaluated. Recently, it turns out that
the alkaline protease (apr£) gene possesses a high level of keratinolytic activity (8).
In an attempt to optirnize the expression of the plasmid (pS I) and to increase its
stability in the cells, a new plasmid called (p5.2) was constructed. The plasmid (p5.2) was
constructed by inserting the complete aprE gene (750 bp) in plasmid pUB 118 and the
expression of the alkaline protease gene in B. subtilis DB 100 was controlled by an earlier
promoter p4J. The size of the new plasmid is shorter (4.7 kbp).
The present study highlights a possible enhancement of feather keratin biodegradation
capability of some feather degrading bacteria via introducing recombinant plasmids
harboring the complete (apr£) gene. Moreover, this work displays an attempt to clarify
certain issue stating that, the alkaline protease produced by the recombinant B. subtilis cells
is actually working as a keratinase like enzyme.