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KMID : 0364820090450040324
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Korean Journal of Microbiology
2009 Volume.45 No. 4 p.324 ~ p.331
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Optimal Culture Conditions for MK1 Strain Isolated from Soft-Rotten Tissue of Neungee Mushroom (Sarcodon aspratus) and the Physico-Chemical Properties of the Purified Exopolysaccharide of MK1
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Ryu Jeong-Eun
Lee Young-Nam
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Abstract
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MK1 strain, an obligate aerobic heterotrophic bacterium isolated from the rotten tissue of Neungee mushroom
(Sarcodon aspratus), produces a copious amount of exopolysaccharide (EPS), which could evoke macrophage activation. Investigations on optimal culture conditions of MK1 and physical properties of MK1 EPS were made. Glucose, galactose, fructose, and sucrose supported well growth of MK1, but potato starch and dextrin did not. However, lactose seemed to be a less favorable carbon source. Optimal growth of MK1 was obtained at pH 7.0, 30oC, and 200 rpm with 2% glucose, and 0.2~0.05% (NH4)2SO4. EPSopt obtained from an optimal growth condition constituted of carbon (37.1%), nitrogen (2.2%), oxygen (49.3%), and hydrogen (6.4%), but no sulfur. Paper chrogromatogram of the acid-hydrolysate of EPSopt suggested that MK1 EPS seemed to be hetropolysaccharide composed of a few number of monosaccharides including amino- and acidic-sugars. Its molecular mass determined by SDS-polyacrylamide gel electrophoresis varied from 14.8 to 47.9 kDa. Physical properties of EPSglu obtained from cell grown in glucose medium, such as relative viscosity (rel) and crystalline morphology were rather affected by pH of the growth medium. Relative viscosity (rel) of exopolysaccaride (0.1g/ml) harvested from cells grown at medium pH ranging from 6.0 and 7.5 was 1.23 and 1.39, respectively. The freeze-dried exopolysaccharide obtained at low pH (6.0 and 6.5) was fine crystaloid and water-soluble, whereas those obtained at high pH (7.0 and 7.5) was rather gluey and less water-soluble.
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KEYWORD
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exopolysaccharide, heteropolysaccharide, MK1 strain, Neungee (Sarcodon aspratus), optimal culture, rotten tissue
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