Production and characterization of exopolysaccharides from submerged culture of Phellinus linteus KCTC 6190

Abstract

The optimal temperature and initial pH for both mycelial growth and exopolysaccharide (EPS) production in shake flask cultures of Phellinus linteus KCTC 6190 were found to be 30 °C and pH 4.0, respectively. Optimal medium composition was determined to be sucrose 50 g/l, corn steep powder 3 g/l, KH 2PO 4 0.68 g/l, and CaCl 2 0.55 g/l. Under optimal culture conditions, the maximum mycelial biomass and EPS achieved in a 5-l stirred-tank fermenter indicated 11 and 3.3 g/l, respectively. To the best of our knowledge, this is the highest polysaccharide yield amongst liquid cultures of P. linteus reported in the literature. The three groups of EPSs (designated as Fr-I, -II, and -III) were obtained from the culture filtrates by a gel filtration chromatography on Sepharose CL-4B and the different fractions were analyzed directly using the size exclusion chromatography coupled with multi-angle laser-light scattering (SEC/MALLS) analysis. It was revealed that all fractions of EPS were polysaccharides consisted of mainly mannose, galactose, and glucose. The molecular weights of Fr-I, -II, and -III of EPS were determined to be 433,400 (±7801), 31,470 (±283), and 12,950 (±90) g/mol, respectively. The SEC/MALLS analysis revealed that molecular dimension of the Fr-I was a spherical form, whereas the Fr-II was a random coil in an aqueous solution.