Exopolysaccharides from Pleurotus pulmonarius: Fermentation Optimization, Characterization and Antioxidant Activity
Jin-Wen Shen1, Chao-Wen Shi1 and Chun-Ping Xu2*
1College of Life Science, Henan Agriculture University, Zhengzhou, 450002 Henan, PR China
2College of Food and Biological Engineering, Zhengzhou University of Light Industry, Zhengzhou, 450002 Henan, PR China
Article history:
Received September 4, 2012
Accepted July, 2013
Key words:
fermentation optimization, Pleurotus pulmonarius, morphological and rheological properties, exopolysaccharide production, thermogravimetric analysis, antioxidant activity
Summary:
Culture conditions for exopolysaccharide (EPS) production by Pleurotus pulmonarius in submerged culture are optimized. The suggested medium composition was as follows: 60 g/L of xylose, 6 g/L of soy extract, 5 mM of KH2PO4 and 5 mM of MgSO4. Under the optimized culture conditions in a 5-litre stirred tank fermentor, the maximum concentration of EPS was 6.36 g/L. Furthermore, the morphological parameters (i.e. average diameter, circularity, roughness and compactness) of the pellets and the broth viscosity are characterized. It has been proven that mycelial morphology and broth viscosity may be the critical parameters affecting the EPS yield. After deproteinization using Sevag method, a group of EPS (designated as fraction) was obtained from the culture filtrates by gel filtration chromatography. FT-IR analysis of the purified EPS revealed prominent characteristic groups corresponding to polyhydric alcohols. GC analysis showed that the purified EPS were mainly composed of galactose and glucose. Furthermore, thermogravimetric analysis indicated that the degradation temperature of the purified EPS was 217 °C. Finally, the antioxidant activity of the EPS fraction was investigated and the relationship with molecular properties was discussed as well.
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