Submerged cultures of basidiomycetes can be used to obtain polysaccharides in a shorter time, when compared to the production and extraction process of mushroom fruiting bodies. This encouraged many authors to develop a variety of culture media to optimize the production of these polymers. In this paper it was observed that the mannans isolated from submerged culture of mushrooms (Ganoderma lucidum and Pleurotus spp.) are very similar to yeast mannan, suggesting that these polymers could have arisen from yeast extract used in the culture media, and were not being produced by the basidiomycetes. Therefore, when yeast extract is used in the culture media in the submerged culture of basidiomycetes, a part of the fraction assumed as EPS is composed of yeast extract polysaccharides.