الفهرس 
Factors affecting chitin production from shrimp shell wasteزOnly 14 pages are availabe for public view
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Abstract
The main study focused on separation of chitin from crustacean
waste (shrimp shell) using some proteolytic bacterial isolates. After that, chitosan was obtained
by deactylation and its characteristics were studied using some characterizing tools. The produced
chitosan was degraded to different molecular weights and evaluated as an antibacterial agent.
Seventy bacterial isolates were obtained from different sources (soil, plant roots and shrimp shell
waste) and tested for their ability to produce proteolytic enzymes. One isolate was selected, due
its high proteolytic activity and ability to grow using shrimp as carbon and nitrogen source on
shrimp shell agar medium and identified as Bacillussubtilis NA12 by 16S-rRNA gene sequences with a
high degree of similarity (99 %) as a gene bank database.
Factors affecting deproteinization (DP) and demineralization (DM) efficiency of shrimp shell waste
(SSW) (carbon source and its optimal concentration, shrimp shell waste concentration, inoculum size
and fermentation time) were studied. The most efficient DP (92.40 %) and DM (81.37 %) of SSW by
B.subtilis NA12 were sucrose 10 % (w/v)
and inoculum size 15 % (v/v 35 x 108 CFU/ml )to ferment shrimp shell
waste 5 % (w/v) for 6 days of fermentation time.
The effect of γ-irradiation on the performance of selected bacterial strain was studied to maximize
chitin yield. Box-Behnken design using response surface methodology was employed to establish the
relationship between the previous variables, implied that the model was highly significant. It was
found that a sucrose concentration of 5 % (w/v), SSW of 12.5 % (w/v), inoculum size of 10
% (v/v) and fermentation time of 7 days; had a predicted value of DP of 97.65 %
whereas the actual experiment gave 96.37 %. The predicted value of DM was 82.94 % whereas the
actual experiment gave 82.19 %.
Chitosan polymer was successfully prepared by the deacetylation reaction from fermented shrimp
shell waste (SSW) by Bacillus subtilis NA12 (crude chitin). Extracted chitin was exposed to
different gamma radiation doses ranged from 5 to 35 kGy in equal kGy interval. The degree of
deacetylation (DDA %) was determined by potentiometric titration. The structural properties of the
two prepared polymers, chitin and chitosan, were characterized by fourier transform infrared
spectroscopy (FT-IR), X–ray diffraction analysis (XRD) and thermogravimetric analysis (TGA). The
results confirmed that gamma irradiation reduced the time required for deacetylation processes. The
data also showed that the prepared chitosan from different irradiated samples have higher
solubility and DDA%.
The different chitosan samples (CS) obtained from irradiated chitin at 5, 15, 25 and 35 kGy with
different MW (from 4.8 x 105 to 3.7 x 104g/mol) with different DDA values (from 84.4
% to 87.9
%)wasevaluated as antibacterial agent against different pathogenic isolates, Pseudomonas aeruginosa
was the lowest sensitive to the chitosan samples then Staphylococcus aureus followed by Klebsiella
sp. and Escherichia coli.