Extracellular-polysaccharide EPS was extracted from Saccharomyces cerevisiae growth medium after 10 days from incubation at 25oC and pH 7 on liquid Subaroud's medium. The extracted Saccharomyces cerevisiae EPS (ScEPS) was purified using gel filtration chromatography on a sephadex G 100 column. The extracted EPS was found to have a maximum relative viscosity in water (3.43 dl/g) and maximum specific viscosity (2.43 dl /g), while the intrinsic viscosity recorded 1.38 dl /g for S. cerevisiae EPS solutions. The chemical analysis of the extracted polysaccharide was found to contain the following constituents, total carbohydrates 61.79%, uronic acids 28%, conjugated protein 4.8%, hexosamines 0.18%, acetyl groups 0.6%, pyruvate groups 0.35%, phosphate groups 1.4%, sulphate groups and an anionic density equal 0.43 mg alcian blue fixed per mg EPS dry weight. The extracted exopolysaccharides also show the following functional groups under IR spectra (hydroxyl, alkanes, sulphydryls alkenes, carbonyl, methyl, carbonyl of carboxylic acid, phosphates, and sulphates). HPLC analysis for the hydrolyzed ScEPS revealed that the monosaccharide composition of the EPS was as follow arabinose, ribose, galactose, glucose, xylose, rhamanose, mannose, glucuronic acid, galacturonic acid, and unidentified sugar with the following ratios 6.683, 2.934, 1.793, 1.694, 1.943, 1.953, 0.980, 4.298, and 2.697. In addition, NMR analysis for the extracted ScPS showed that the chemical shifts of 13 C from EPS polymer under NMR spectra showed one signal at δ 20 ppm, δ 55 ppm, δ 60 ppm, δ 170 ppm and δ 175 ppm in addition to 8 signals at the range from δ 65 to 85 ppm referring to different chemical groups on the sugars of the polysaccharide.
Key words: Extraction of exopolysaccharides, viscosity of EPS, Chemical analysis of EPS, Characterization of EPS
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