Investigation of exopolysaccharides production in submerged and solid state fermentations

Exopolysaccharides (EPSs) are macromolecular carbohydrates synthesized by various organisms, predominantly microorganisms. EPS productions by Pleurotus spp. were investigated in submerged fermentation (SmF). The best EPS producer and its incubation period were determined as Pleurotus sajor caju and on 5 days, respectively. Then culture conditions for EPS production by P.sajor cajuin SmF were optimized. The optimal initial pH, temperature and agitation rate of culture were determined as 5.0, 25 degree Celsiusand 150 rpm, respectively. The optimized medium composition was as follows (in per liter): 90 g of glucose, 10 g of yeast extract, 10 g of peptone, 100 mM of magnesium sulphate. Under the optimized culture conditions, the maximum concentration of EPS was determined as 33.32g in per liter. Maximum EPS production by solid state fermentation used wet potato peel as a substrate was determined as 0.82 g in per liter.After isolation of EPS from optimized submerged culture conditions, one EPS fractionwas obtained by gel filtration chromatography. FT-IR spectra showed bands characteristic of C-H, C-O-C and C-H-O groups that are present in the structure of partially purified EPS. TLC analysis determined that the partial purified EPS was mainly composed of glucose. The proton NMR spectrum of the partial purified EPS was supported this data.Furthermore, TGA indicated that the degradation temperature of the partial purified EPS was 276.91degree Celsius. Finally, hydroxyl, superoxide and DPPH radical scavenging activities of the partial purified EPS fraction were also investigated.