الفهرس 
REVIEW OF LITERATUREREVIEW OF LITERATUREREVIEW OF LITERATUREREVIEW OF LITERATUREOnly 14 pages are availabe for public view
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Abstract
There has been a great concern from scientists to investigate marine microorganisms as a new source of pharmaceutical, antimicrobial and industrial compounds. Several types of carbohydrates showed biological activities such as anticoagulant, fibrinolytic, antimicrobial, and prebiotic effects. Some of these activities are shown by the native forms of carbohydrates and others appeared as a response to structural modifications of the carbohydrate molecule. In the current study, the collected samples were cultivated on Nutrient broth medium. These samples were collected from different marine sources including algae, coral, sediments, urchin and sponge, from Ain Al Sokhna, Red Sea and Qarun Lake marine areas in Egypt. A total of 20 mesophilic bacterial strains were isolated from the above sources. Four bacterial isolates showed the best viscosity in the medium. The selected Klebsiella sp. was first selected from all other marine bacterial isolates, according to its initial production of high culture viscosity and exopolysaccharides. The selected Klebsiella sp. was maintained by monthly subculture on slants of Nutrient agar media. The inoculated slants were incubated at 28-30°C for 1-2 days and the resulted heavy growths were then used for the fermentation experiments or stored at 4 °C. The growing bacterial cultures were examined for their pH, carbohydrate content of the culture filtrates, exopolysaccharide yields, and culture protein content. The Klebsiella sp. identified by 16S rRNA
A– Morphology and microscopy: Colonies were Gram negative bacilli, non-motile and non-spore former
B– Biochemical reactions: Oxidase (-), Catalase (+), Urease (+), and tests of Indole (-), Voges-Proskaur (-) and Citrate (+)
C– 16S (rRNA) and Sequencing techniques: The 16S rRNA gene is used for phylogenetic studies as it is highly conserved between different species of bacteria and archaea.
This selected strain was used for production of exopolysaccharide. The high exopolysaccharide yield was achieved by optimization of different environmental conditions (shaking speed, pH and incubation time), fermentation carbon source (glucose, fructose, sucrose, glycerol and sodium tri-citrate), fermentation Nitrogen source (peptone, casein hydrolysate, tri- ammonium citrate, ammonium sulfate and urea) and inorganic salts (K2HPO4, MgSO4, and MnSO4). The best yield of exopolysaccharide in the current study after optimization of different fermentation parameters which was 8.92 (g/l). So, we can notice that, the current study achieved a significantly high yield of exopolysaccharide. The native form of the exopolysaccharide and its modified form were tested for different biological activities. This exopolysaccharides showed an antimicrobial activity against E.coli and Staphylococcus aureus but it had not antimicrobial activity against Candida albicans and it did not show probiotic effect. However, further studies may be required on these biopolymers to test it against other fungal and bacterial strains.
It can be noted that the best exopolysaccharide production depends on the selected microorganism, component of the medium, environmental conditions and all related parameters. The bacterial exopolysaccharide has many documented activities. Several exopolysaccharides produced by microorganisms from extremes habitats (temperature, salinity and nutrient availability) show biotechnological promise. By examining their structure and chemical–physical characteristics, it is possible to gain insight into commercial application and they are employed in several industries ranging from pharmaceutical to food-processing fields, through to the detoxification capability of polluted areas from petrochemical oils. Further study of the produced exopolysaccharide, is required to test its activities and its possible applications.