Characteristics of Exopolysaccharides from the Citrine Oyster Mushroom, Pleurotus citrinopileatus (Agaricomycetes), Depend on the Nitrogen Source in the Medium.

We investigated the effect of peptone and (NH4)2SO4, used as nitrogen sources in a submerged medium, on the molecular weight and carbohydrate compositions of exopolysaccharides (EPSs) produced by the culinary-medicinal mushroom Pleurotus citrinopileatus. When (NH4)2SO4 was used instead of peptone, it yielded more specific EPSs, producing 32.80 mg EPS/g dry mycelial biomass, but small amounts of EPS and mycelial biomass. These nitrogen sources also resulted in the production of different net charged EPSs, according to crude fractionations on a DEAE Sepharose Fast Flow column. Purified EPSs were initially repurified by gel filtration chromatography, and the profiles indicated that a range of EPSs with different molecular weights were collected through the use of this strategy. Analysis of the carbohydrate composition of purified EPSs demonstrated that the main component produced by P. citrinopileatus in a glucose-(NH4)2SO4 medium, with an estimated molecular weight < 10 kDa, was rich in glucose (95.9%), and its structure could consist of glucan. Conversely, this mushroom produced diverse heteropolysaccharides (11.1-42.3% mannose, 6.3-80.3% glucose, 0.3-49.2% N-acetylgalactosamine, and 7.6-26.3% N-acetylglucosamine) in a glucose-peptone submerged medium. By applying various nitrogen sources in submerged medium, these results could be used to improve the possibility of obtaining molecules similar to those found in the fruiting bodies of the same mushroom species grown in conventional culture.