الفهرس 
INTRODUCTIONOnly 14 pages are availabe for public view
 |  | from | 226 |  |  |
| | | from | 226 | | |
Abstract
Microbial exopolysaccharides (EPSs) are very large molecules that are produced outside of cells in the form of capsules or slime layers. Multiple microorganisms, such as bacteria, yeasts, fungus, and algae, have been examined for their capacity to generate EPSs. Microbial extracellular polymeric substances (EPSs) can be classified as either homopolysaccharides or heteropolysaccharides, and they exhibit many characteristics including variations in monosaccharide compositions, structural conformations, molecular weights, and functional groups.
The current study has been performed on collection of marine samples from different locations. samples were collected from Hurghada, Safaga and Marsa Alam. Then, the serial dilution method was used for isolation of streptomycetes using starch nitrate agar medium. Twenty-two isolates were isolated in order to be screened for their capability to production of EPS in a liquid production medium. Then, the antioxidant activity of different bacterial exopolysaccharides was determined at different times against DPPH free radical.
The promising streptomycete isolate which produced EPSs having the highest antioxidant activity (S10) was subjected to biochemical, morphological, and physiological identification. While, Phylogenetic analysis based on the 16S rRNA gene sequence was done for S10 and compared to reference 16S rRNA gene sequence available in the GenBank and EMBL database obtained from the National Centre of Biotechnology Information database using BLAST search (http://ncbi.nlm.nih.gov/ BLAST/). So, it was identified as Streptomyces sp. MAE with accession number OR354383.
Optimization of the environmental and nutritional parameters and the medium contents and their concentration play important roles for increase maximum yields of EPS and its activity. Maximum EPS productivity by Streptomyces sp. MAE (7.80 g/l) cell dry weight (6.5 g/l) was obtained after 6 days of incubation, and maximal yield was noticed at pH 7.0 (7.8 g/l) and cell dry weight (6.3 g/l). While, the maximal EPS production (7.7 g/l) at cell dry weight (6.2 g/l) was noticed at 30°C. Thus, maximal yield at 150 RPM was (8.0 g/l) and cell dry weight (6.5 g/l). Therefore, from all the diverse nitrogen sources tested, Peptone was supported maximal EPS output (8.2 g/l) with cell dry weight (6.7 g/l) and Starch was supported maximal yield (8.4 g/l) at cell dry weight (6.8 g/l).
Streptomyces sp. MAE was subjected to cultivation, isolation, and fractionation of its EPS. The major fraction EPSS10 from three volume absolute ethanol. Fraction EPSS10 was containing uronic acid (19.55%). Therefore, the fraction had sulfate (25.03%). While, N-acetyl glucose amine (10.63%). Molar ratio was determined using HPLC showed that EPSS10 fraction containing monosaccharide composition Glucose: Rhaminose: Glactouronic acid: Xylose: Arabinose with molar ratio 2.0:1.0:1.0:0.5:0.5, this means the fraction was acidic heteropolysaccharides. While, the toxicity studies performed on EPSES10 was found to be safe up to 5 g/kg
Antioxidant activity of EPSS10 was conducted using several methods (DPPH, ABTS, Fes2+ ion chelation ability, Lipid peroxidation Inhibition capacity, O2- radicals scavenging capacity, NO scavenging capacity), it gives 89.21±0.32, 75.39±0.47 %, 68.32±0.99%, 78.57±1.24 %,
85.5±0.90% and 65.24±0.58%, respectively.
Anti-inflammatory activity was determined for EPSES10 by using different ways as Lipoxygenase (COX1) inhibitory gave IC50 233.86 µg
/ml, while control sample (Celecoxib) gave IC50 45.33 µg /ml. therefore, cyclooxygenase (COX2) inhibitory gave 77.32±0.16 µg /ml, while control (Celecoxib) gave 93.09±1.58 µg /ml.
By Using MTT viability assay, the fraction EPSS10 had cytotoxic effect on different tumor cell lines, IC50 value was calculated to be 858.51±3.33, 104.39±1.24, 78.12±0.86, 317.33±1.92, 210.83±0.72 and
449.31±2.91 µg/ml for cell lines HepG2, CaCo-2, MCF-7, PC3, A549 and PANC1, respectively. While, by using MTT viability/cytotoxicity assay maximum nontoxic concentration (MNTC) was determined to be the highest dose was used in antiviral activity determination. Cytotoxic effect of EPSS10 was evaluated against African Green Monkey Kidney (VERO) cell line and half maximal cytotxic concentration (CC50) was (616.40±27.91 µg/ml) and MNTC was (1000 µg/ml). Antiviral activity was evaluated against Hepatitis A virus (HAV) and Herpes simplex virus 1 (HSV-1). EPSS10 showed no activity on Herpes simplex virus 1 (HSV-1), while showed (57.29 ± 1.78) antiviral activity against HAV, at 1000 µg/ml. The half maximal viral cytopathogenicity inhibitory concentration (EC50) of EPSS10 was (838.50 ± 34.62 µg/ml µg/ml) against HAV.