Effect of nutritional and environmental conditions on the production of exo-polysaccharide of Agaricus brasiliensis by submerged fermentation and its antitumor activity

Mushrooms have become attractive as a functional food and as a source for the development of drugs and nutraceuticals. A. brasiliensis is considered as the best among them. There are several published works on the fruiting bodies of this mushroom, showing high antitumor activity. The mycelium polysaccharide and exo-polysaccharide (EPS) of this mushroom also demonstrated a strong antitumor action. However, there is little information available in the literature about the optimization of physical and chemical conditions for production of EPS by submerged fermentation (SmF). After initial screening from the five strains available in the LPB Culture Collection, A. brasiliensis LPB 03 was selected for EPS production in SmF. Studies on supplementation of a carbon source to the medium revealed that sucrose was most effective for EPS production. Yeast extract was the best for EPS among the inorganic and organic nitrogen sources tested. The factorial experiment demonstrated that a temperature of 30 °C and a pH of 6.1 were the best for the EPS production. Glucose 10 g/l, yeast extract 3 g/l, K2HPO4 0.6 g/l and MgSO4 0.3 g/l were most suitable for the EPS production. Maximum EPS production was obtained in the static condition with manual agitation two times per day after a 1-week culture (382 mg/l), increasing by 78.62% more than that before optimization. In the bioreactor with aeration and agitation, the maximum EPS was produced at 321.2 mg/l. The EPS of A. brasiliensis produced in SmF showed strong inhibition against Sarcoma 180 in mice, reaching 72.19% inhibition compared with the control group. Furthermore, 50% of mice in the test group demonstrated total tumor regression.