Submerged cultivation of Ganoderma lucidum biomass and immunostimulatory effects of fungal polysaccharides

Abstract

Original Ganoderma lucidum strain MZKI G97 isolated from Slovenian forests was cultivated in a liquid substrate based on potato dextrose and olive oil. The influences of inoculum and oxygen partial pressure in batch and fed batch cultivation in a 10-l laboratory stirred tank reactor were studied. Fungal biomass was found to be oxygen and shear sensible. Using a 17% (wet weight) 6 days old vegetative inoculum, 9.6 g l −1 of dry biomass in batch cultivation and 15.2 g l −1 in fed batch process were obtained. Extracellular (9.6 g l −1) and intracellular (6.3 g l −1) polysaccharide fractions were isolated. Extracellular polysaccharide fraction and four intracellular polysaccharide fractions were obtained. Polysaccharides were further separated by ion-exchange, gel and affinity chromatography. The isolated polysaccharides were mainly β- d-glucanes. Immunostimulatory effects of isolates were tested on induction of cytokine (tumour necrosis factor α (TNF-α) and interferon γ (IFN-γ)) synthesis in primary cultures of human peripheral blood mononuclear cells (PBMC) isolated from a buffy coat. The TNF-α inducing activity is comparable with romurtide, which has been used as a supporting therapy in cancer patients treated with radiotherapy and/or chemotherapy.