Extraction optimization and bioactivities of an extracellular polysaccharide produced by Aspergillus fumigatus

Aspergillus fumigatus produces an extracellular polysaccharide, AFEPS, when grew in NaOH solution pretreated rice-straw medium. A three-level, three-factor Box–Behnken design (BBD) response surface methodology (RSM) was applied to optimize the extraction parameters of AFEPS. RSM analysis indicated good correspondence between experimental and predicted values. The optimal conditions for polysaccharide were: precipitation time 10.9 h, pH 5.2 and ethanol concentration 90%. AFEPS was composed of arabinose, xylose and glucose in a molar ratio of 1.05:5.36:10.83, its average molecular weight was estimated to be about 36.2 kDa. Evaluation of the antioxidant activity in vitro suggested that AFEPS had high scavenging activity for superoxide anion and hydroxyl radicals. AFEPS exhibited excellent antitumor activities both in vitro and in vivo while showing no damage to normal cells.