الفهرس 
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Abstract
This thesis aimed primarily at investigating the potential of cyanophycin production of some selected cyanoprokaryotes. For this purpose, nine different cyanobacteria species namely. Oscillatoria obscura, Anabaena anomala (isolate 1), Anabaena anomala (isolate 2), Anabaena oryzae, Anabaena khannae, Nostoc kihlmani, Nostoc sp., Synechococcus sp., Spirulina platensis, were selected as test organisms. The cyanobacteria species were grown in standard BG11 nutrient medium and incubated for 30 days under favorable growth condition at 25±2oC and with continuous light of 2.789 wm-2. Different test cyanobacteria exhibited wide variations in both biomass (0.25 - 0.8 freeze-dry wt g l-1) and cyanophycin content (0.03-0.224g l-1). The experimental results indicated that the cyanobacterium Anabaena anomala (isolate 2) maintained relatively higher biomass production and CGP content. Therefore, this cyanobacterium was selected for further screening growth experimental design to define the best growth medium composition (mgl-1). Compared to control, the results indicated that the modified composition of BG11 (2250 mg NaNO3, 60 mg K2HPO4, 112.5 mg MgSO4.7H2O, 54 mg CaCl2.2H2O, 3.0 mg citric acid, 9 mg ferric ammonium citrate, 1.5 mg EDTA, 30 mg Na2CO3 , 0.031 mg H3BO3, 0.255 mg MnSO4.H2O, 0.143 mg ZnSO4.7H2O, 0.0038 mg CuSO4.5H2O, 0.0063 mg (NH4)6Mo7O24.4H2O, 25 ml Soil solution and 500mg NaCl) increased the biomass production by 86.25% (from 0.8 gl-1 to 1.49 gl-1) and cyanophycin content by 96.43% (from 0.224 gl-1to 0.44 gl-1). Amino acids composition of crude cyanophycin of Anabaena anomala (isolate2) grown on BG11 medium (control) and that grown in the modified optimized medium were analyzed and compared. The result indicated that the concentration of aspartic acid and arginine increased by 65.26% and 16.7%, respectively, compared to control. Electron microscopy highlighted that cell of Anabaena anomala isolate2which grown in optimized BG11 contain more conspicuous cyanophycin granules with relatively higher number and size compared control culture. Based on these results it has become evident that modified BG11medium composition induced highly significant (p ≤ 0.01) increase in both biomass production and CGP content of cyanobacterium Anabaena anomala (isolate 2) and open new research window for further large ‐ scale growth experiments.