Thesis (M.Sc.) - Cairo University - Faculty of Science - Department of Botany - Microbiology

The cyanbacterium Spirulina is an ideal nutritional supplement and can be the answer to malnutrition problems in developing countries. In order to increase the economical value of spirulina platensis (isolated from Egyptian localities), spirulina at the logarithmic growth stage was exposed to different doses of gamma irradiation (0.0, 0.5, 1.0, 1.5, 2.0, 2.5 and 3.0 kGy) using Co60 as a gamma source at the cyclotron unit, nuclear research center, Egyptian atomic energy authority. The irradiated and non - irradiated cultures were incubated in optimum growth conditions for 10 days. The maximum growth (expressed as O.D. at 560 nm), and the contents of photosynthetic pigments; chlorophyll a and carotenoids, were observed at the dose of 2.0 kGy then a significant decrease occurred at the dose of 2.5 kGy. Whereas, the dose of 3.0 kGy caused damage of the organism under investigation. The photosynthetic activity reached maximum value at 2.0 kGy. The response of carboxylating enzymes to gamma rays was greatly different; reaching maximum activity in specimen irradiated with one and two kGy for phosphoenol pyruvate carboxylase and ribulose 1, 5 bisphosphate carboxylase respectively. Total soluble carbohydrates, phenols, activity of antioxidant enzymes (catalase, peroxidase, glutathione peroxidase and super oxide dismutase) gradually increased up to 2.0 kGy above which a significant decrease was observed. In addition, the contents of nucleic acids; vitamins (A, K, B , B , B and B) as well as minerals - N, P, Na, K, Ca, Mg, 1 2 3 6 Fe have the same trend of changes

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