Synthesis and characterization of a novel extracellular polysaccharide by Rhodotorula glutinis |
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Authors: | Dae Haeng Cho Hee Jeong Chae Eui Yong Kim |
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Institution: | (1) Department of Chemical Engineering, The University of Seoul, 130-743 Seoul, Korea;(2) Department of Food Technology, Hoseo University, 336-795 Asan, Korea |
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Abstract: | The aim of this work was to characterize an exopolysaccharide by Rhodotorula glutinis KCTC 7989 and to investigate the effect of the culture conditions on the production of this polymer. The extracellular polysaccharide
(EPS) produced from this strain was a novel acidic heteropolysaccharide composed of neutral sugars (85%) and uronic acid (15%).
The neutral sugar composition was identified by gas chromatography as mannose, fucose, glucose, and galactose in a 6.7:0.2:0.1:0.1
ratio. The molecular weight of purified EPS was estimated to be 1.0−3.8×105 Dalton, and the distribution of the molecular weight was very homogeneous (polydispersity index =1.32). The EPS solution
showed a characteristic of pseudoplastic non-Newtonian fluid at a concentration >2.0% in distilled water. The maximum EPS
production was obtained when the strain was grown on glucose (30 g/L). Ammonium sulfate was the best suitable nitrogen source
for EPS production. The highest yield of EPS was obtained at a carbon to nitrogen ratio of 15. The EPS synthesis was activated
at the acidic range of pH 3.0–5.0 and increased when the pH of the culture broth decreased naturally to <2.0 during the fermentation.
When the yeast was grown on glucose (30 g/L) and ammonium sulfate (2 g/L) at 22°C at an initial pH of 4.0, EPS production
was maximized (4.0 g/L), and the glucose-based production yield coefficient and carbon-based production yield coefficient
were 0.30 g of EPS/g of glucose and 0.34 g (carbon of EPS)/g (carbon of glucose), respectively. |
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Keywords: | Rhodotorula glutinis exopolysaccharide extracellular polysaccharide characterize uronic acid molecular weight culture conditions |
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