Papers by Keyword: Exopolysaccharide

Abstract: The novel exopolysaccharide (EPS) was produced by a streptococcus thermophilus strain isolated from Tibetan kefir grain, and it was purified using DEAE cellulose 52 and DEAE Sepharose CL-6B column chromatography. Then it was eluted as a single symmetrical narrow peak on high-performance gel-permeation chromatography (HPGPC) and the average molecular mass was estimated to be 30,092Da. Infrared spectrum analysis indicated it had characteristic glycosidic structures. Gas chromatography showed that the EPS is composed of mannose and glucose in a molar ratio of 2.6:1 with trace galactose. The structural features of EPS were investigated by partial hydrolysis with acid, methylation analysis and NMR spectroscopy analysis. The results revealed that the main backbone chain of EPS was (23)-β-D-Manp, (34)-β-D-Manp, (23,6)-α-D-Glcp and trace amounts of galactose.

Abstract: The open culture is a simple, low-cost way for microalage cultivation, and the great advantage of which is that it can be easily used for mass production. This culture system is primarily used for the alga that can survive under bad or extreme conditions. N. flagelliforme is a kind autotrophic alga having the property of alkali-resistance, which makes open culture of N. flagelliforme become possible. In this study, the cultivation of N.flagelliforme with an open, 60×40×30cm rectangular glass reactor was conducted. Firstly, the open culture of N.flagelliforme was carried on without new nutrient elements supplemented into pond intermittently. During the whole process of cultivation, the pH maintained at 8-9 in order to avoid the contamination of other green alga. At the end of the cultivation, the cell density reached 0.802 g•L^-1 and the exopolysaccharide concentration was 97mg•L^-1. Secondly, the fed-batch cultivation was employed to increase biomass and exopolysaccharide production. At the end of the fed-batch cultivation, the biomass and exopolysaccharide of N.flagelliforme increased distinctly to 1.16 g•L^-1 and 124 mg•L^-1, respectively.

Abstract: This paper is an attempt to study the growth line of poria cocos through flask culture experiment, and leads to a discussion of different fermentation conditions. The optimum media for mycelial growth were determined as (g/l): glucose 60, peptone 10, KNO₃ 10, KH₂PO₄ 3, and MgSO₄ 1; while for exopolysaccharide was (g/l), glucose 40, peptone 5, KNO₃ 5, KH₂PO₄ 0.5, MgSO₄ 1. The optimum initial pH value of medium was 5.5, inoculation, 10% (v/v) and different liquid volume had minimal influence on the mycelial growth and exopolysaccharide production.

Abstract: In this work, exopolysaccharide (EPS) production by the yeast Rhodotorula glutinis was investigated. The results suggest that the synthesis of EPS in batch fermentations was enhanced by using a low C/N ratio to stimulate fast cell growth during the exponential phase and by adding glucose to stationary phase cultures to provide excess carbon for EPS formation. The apparent viscosity and molecular weight of EPS were found to decrease with increasing fermentation time due to the partial hydrolysis of EPS by the acidic fermentation broth (pH 1.8). Maintaining stationary phase cultures at pH 4 was found to be effective in minimizing acid hydrolysis and producing EPS with high molecular weight and apparent viscosity.

Abstract: The self-aggregation of polysaccharides (PS) in solution has led to high viscosity, unstable biological activity and poor resolution in instrumental characterization as well. In this work, ultrasound with low power level was applied to disrupt the PS aggregation of an exopolysaccharide(EPS) from Cordyceps sinensis mycelial culture. Ultrasonic irradiation with 20% amplitude (about 4 W) for 0.5 min decreased the specific viscosity of EPS by 59%. Dynamic light scattering(DLS) experiments on native EPS showed four distinct population with diameter range of 10~500 nm, 500~2500 nm, 3500~12300 nm and 22150~115400 nm respectively. The peaks at large size range in the intensity-weighted size distribution disappeared or shifted to small size range, indicating a gradual disassociation of EPS with the prolongation of ultrasonic duration. AFM observation proved the disassociation of EPS from a highly across-linked gel into single strand under ultrasonic treatment. According to DLS analysis, ultrasonic treated EPS did not show any sign of aggregation over 8 days in contrast to an immediate aggregation growth with native EPS. Ultrasonic irradiation control PS association by means of weakening the hydrogen bonds through the hydrodynamic shear forces arising from acoustic cavitation in the irradiated liquid, which has importance in the applications and structural characterization of PS.

Abstract: Agaricus brunnescens is a producer for novel biomaterial (exopolysaccharide of Agaricus brunnescens). In this paper, the optimization of culture conditions for the biomass of Agaricus brunnescens through orthogonal methods was reported. The optimal conditions for enhancing production was: inoculum size 10 %, broth volume 100 mL in a 250 mL flask, pH 6.0. This optimization strategy in shake flask culture lead to an biomass 0.8 g/L, which was considerably higher than that obtained in preliminary studied.

Abstract: Ypsizigus marmoreus is a newly cultivated medicinal and edible mushroom with higher antitumor activity. In this paper, a uniform design was used to optimize the medium formula with four factors each at six levels, and a regression model was constructed to predict the antitumor exopolysaccharide production. The optimal concentrations for the enhanced exopolysaccharide production were determined as 30% (w/v) glucose, 8.4% (w/v) soybean peptone, 3% (w/v) KH₂PO₄ and 30% (w/v) sweat potato flour. Subsequent experiment confirmed the validity of the model. Under the optimal condition, exopolysaccharide yield reached 3.39g/L in shake-flask culture, which was 3.53 fold higher than that obtained in the basic medium. The results highlight the future application of optimized medium for high yield production of antitumor exopolysaccharide by fermentation of Hypsizigus marmoreus.

Abstract: The exopolysaccharide of Agaricus brunnescens is a novel biomaterial for various uses. In this paper, the optimization of simple media for the exopolysaccharide production by Agaricus brunnescens through orthogonal methods was reported. The optimal medium for enhancing production was (g/L): glucose 40, yeast extract 5, KH2PO4 0.5. This optimization strategy in shake flask culture lead to an exopolysaccharide production of 1.8 g/L, which was considerably higher than that obtained in preliminary studied.

Abstract: To find a novel exopolysaccharide, marine bacterial strains were isolated from coastal regions of Korea. Strain 00SS11568 was then selected as it produced a mucous exopolysaccharide during the stationary phase in a batch culture. The isolate was identified as Alteromonas sp. based on its 16S rDNA sequence, morphological, and biochemical properties. The exopolysaccharide, designated as p-11568, exhibited an emulsifying ability. The Emulsification Index (E24) of 0.1% p- 11568 was 77.4% with an emulsified kerosene content, and was higher than those of commercial polysaccharides, such as xanthan gum (26.1%), gellan gum (1.3%), and sodium alginate (2.0%). p- 11568 was found to be composed of glucose and galactose as the main natural sugars in a molar ratio of 1.3:1, along with uronic acid (18.9%, w/w) and sulfate groups (1.2% w/w). The average molecular mass was 4.4 x 105 daltons by gel filtration chromatography. The effects of pH, temperature, inorganic compounds, and C and N sources were tested to obtain the optimal medium composition for the production of p-11568. Under optimal growth conditions with the M-11568 medium, 14.9 g of crude p-11568 per liter was obtained.