A medicinal mushroom Fomes fomentarius, was isolated from the fruiting body of a wild F fomentarius and identified by ITS-5.8S rDNA sequencing analysis. Then, the optimization of submerged culture conditions and nutritional requirements of mycelial biomass and exopolysaccharide (EPS) production from F fomentarius was studied using orthogonal matrix method. Under the optimal culture condition, the maximum EPS concentration reached 3.64 g 1(-1), which is about four times higher than that at the basal medium. Furthermore, the EPS from F. fomentarius has a direct antiproliferative effect in vitro on SGC-7901 human gastric cancer cells in a dose- and time-dependent manner. Moreover, it was about three times that EPS at noncytocxity concentration of 0.25 mg ml(-1) could sensitize doxorubicin(Dox)-induced growth inhibition of SGC-7901 cells after 24 h treatment. (c) 2007 Elsevier Ltd. All rights reserved.