Subcritical water extraction of Ganoderma lucidum strains and characterization of their compounds

In this study, polysaccharides of two different Ganoderma lucidum local strains called ?Balcali? and ?Alata? were extracted with subcritical water at CO2 atmosphere. Subcritical water extraction was carried out at three different temperatures (50, 100 and 150 ºC) at a constant pressure of 280 bar to examine physical and chemical characterization of the polysaccharides extracted. The solubility, pH, humidity, protein, uronic acid, and monosaccharide contents, and molecular weight distribution of polysaccharides in each extract were determined. Monosaccharide contents and the average molecular weights of the extracts were determined by GPC and HPSEC-MALLS analysis. The results showed that polysaccharides of both strains of Ganoderma lucidum composed of mainly Dglucose and trace amount of D-mannose and D-galactose. HPSEC-MALLS analysis were indicated that both strains contained two polysaccharide fractions. The weightaverage molecular masses of first fraction in Alata were 1.253x107, 5.924x106 and 2.901x106 Da and in Balcali were 6.279x106, 1.749x106 and 8.140x105 Da at 50, 100, and 150 ºC, respectively. The second fraction had weight average molecular weight (Mw) of 5.064x104, 4.687x104 and 1.022x104 Da for Alata and 4.311x104, 2.662x104 and 2.672x104 Da for Balcali at 50, 100 and 150 ºC, respectively. HPSEC-UV analysis at 280 nm and Lowry protein assay results showed that these polysaccharide extracts contained protein. The amount of protein in polysaccharide extracts decreased by increasing the extraction temperature. All subcritical water extracts of Balcali and Alata were soluble while hot water extracts left insoluble residues of 1.53% and 3.43% in neutral and alkali medium, respectively. KeyWords: Ganoderma lucidum (Reishi), subcritical water extraction, polysaccharide, molecular mass distrubition