الفهرس 
AbbreviationOnly 14 pages are availabe for public view
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Abstract
The present study was carried out in order to select the production of exopolysaccharides by some fungi. These substances have been tested with the purpose of finding potential applications for prevention of human diseases such as cancer, hypoglycemia and hypercholesterolemia. The study began with screening 15 fungal strains to choose the best EPS producers. This procedure was carried out on surface liquid culture using two types of media the first medium contains glucose, 2; peptone, 0.2 and yeast extract 0.6 gm/100 ml. This medium was used for growing the basidiomycetes group. The other medium is modified Dox medium, which has been used for growing the rest of the fungal group. All cultures were incubated for 10 days at 33 <U+F0B1> 2<U+F0B0>C and pH 6. It has been found that Pleurotus pulmonarius was the best EPS producer so further studies on this fungus were carried out to elucidate the effect of different cultural parameters for EPS production in submerged culture at 33 <U+F0B1> 2<U+F0B0>C and pH 6 and the results are summarized as follows: The highest EPS production was obtained on malt medium and 1.5 % malt extract proved to be the best concentration. ,The highest exopolysaccharides production was obtained after 10 days incubation.,The pH optimum for exopolysaccharides production was 5.5.Glucose was the best stimulator for exopolysaccharides production with 5.5 % glucose as the favored concentration., 0.4% (w/v) potassium nitrate proved to be the best stimulator for exopolysaccharides production.,Suitable incubation temperature for exopolysaccharides production was found to be 30 <U+F0B0>C. At the end of these series of experiments we have obtained 280 mg/100 EPS by Pleurotus pulmonarius when grown on 1.5 malt extract medium containing 5.5 % glucose, 0.4 % potassium nitrate and pH 5.5and incubated for 10 days incubation periods at 30 <U+F0B0>C. We have obtained three kinds of polysaccharides of P. pulmonarius extracted from either from culture broth of malt media (CBMM), culture broth of yeast extract media (CBYM) and Hot water extract of fruit body of the fungus (FBHWE). The physicochemical characterization of the polysaccharides (CBMM) and (CBYM) showed that they were hardly solubilize except in hot water at 60 <U+F0B0>C for 8 hours where a small portion of the crude polysaccharides was dissolved and the remaining residues were dissolved in hot DMSO at 60 <U+F0B0>C for 2 hours,The determination of monomers of their neutralized acid hydrolyzate by paper chromatography showed that they are composed of glucose, mannose and galactose. Measuring the melting points of their hexosasone showed that they have the melting point ranges of these monomers. The polysaccharide (FBHWE) showed more solubility in hot water and composed of Glucose and xylose as main components. The structure was confirmed by the infrared spectroscopic analysis (IR) which showed that these substances mainly are <U+F062> and <U+F061> glucan with (1,3) and (1,4)linkage as indicated from their characteristic peaks.The periodate oxidation of these polysaccharides imply the presence of (1,6)linked glucan. Also, the present study was suggested to evaluate the biological activities of the three polysaccharide samples extracted from Pleurotus pulmonarius as antitumor agent in vitro and in vivo. The cytotoxicity test in vitro had no effect on the tested cell lines. The in vivo study was conducted using Ehrlich ascites carcinoma (EAC) cell line intrapertoneally injected mice. The study was designed as four group of mice each contain 6 tumorbearing mice. Three groups each received one of the polysaccharide sample (CBMM), (CBYM) or (FBHWE). These samples were dissolved or suspended in physiological saline and administered intrapertoneally daily for 8 days after tumor transplantation (day 0). The fourth group was tumorbearing mice received 0.2 ml physiological saline solution and injected in the same manner. The mice were sacrificed, livers and sera of each mouse were collected on which some biochemical parameters were investigated. The antitumor activity was evaluated and the results were statistically analyzed and summarized as follows: An extremely significant reduction of the tumor volumes in tumor bearing mice treated with the three substances was noticed compared with those salinetreated tumorbearing mice. This reduction in tumor volume was accompanied with a significant reduction in both liver DNA and RNA in addition to an increase in the total lipids and proteins after treatment the groups of tumorbearing mice with the polysaccharide samples compared with those salinetreated tumorbearing mice. A significant increase in serum superoxide dismutase (SOD) activity in all groups of EACbearing mice treated with polysaccharide samples compared with those salinetreated tumorbearing mice. Other significant changes were obtained in some serum parameters including cholesterol, triglyceride, high density lipoprotein (HDL) and low density lipoprotein (LDL), These parameters were significantly decreased in sera of tumorbearing mice treated with the three polysaccharide samples compared with those salinetreated tumor bearing mice. from the present study, it may be concluded that, these substances have antitumor activities against Ehrlich ascites carcinoma cell line (EAC) either by acting as artificial superoxide dismutase or stimulation of the production of superoxide dismutase enzyme possibly causing increase H2O2 generation which seemed to be involved in killing of the tumor cells. All the significant correlations in polysaccharides treated tumorbearing mice and those saline treated tumorbearing mice are listed below: Positive correlations were found between liver DNA contents and RNA, cholesterol, HDL and triglycerides. On the contrary, negative correlations were found between liver DNA and both liver total lipids and proteins. On the other hand, There was a negative correlation between liver total protein contents and RNA. Finally, negative correlations between serum SOD and both sera LDL and cholesterol were observed.The results of the present study have been discussed on the light of the previous literature. Since these substances had no cytotoxic effect in vitro, it has been found that the mode of action of these substances as antitumor agents is based on the activation of immunological function in host and increasing the body resistant against tumor. Finally, It is recommended to use the polysaccharides extracted either from the fruit body of P. pulmonarius or its culture broth as antitumor agents against Ehrlich ascites carcinoma model of cancer and examine these substances on other tumor cell lines. Further studies on isolation, structural elucidation and their mode of action directly related to the antitumor activity of these polysaccharides should be conducted in the future to achieve their use in cancer therapy