Exopolysaccharide extraction from Ophiocordyceps sinensis culture broth supplemented with olive oil

Abstract

Culture broth of Ophiocordyceps sinensis with 5% olive oil (v/v) stimulated production of mycelial biomass and biosynthesis of exopolysaccharide (EPS). Thus, the purpose of this current study is to isolate EPS from the olive oil-containing liquid broth. Initially, the culture broth was concentrated by using a rotary evaporator at 50oC. After removing olive oil by liquid-liquid extraction with three solvents ((hexane, peotroleum ether and diethyl ether), the suspensions were precipitated with ethanol 960 at 3 ratios of 1:3, 1:4 and 1:5 (v/v) and left 24 hours at 4oC. Following this, EPS crudes were obtained by centrifugation at 8000 rpm for 10 min. Finally, the ABTS radical scavenging activity of these EPS crudes was measured and compared. As a result, petroleum ether was selected to remove olive oil in the culture broth. The extraction yield of EPS with 4 volumes of ethanol (v/v) was the highest reached at 17,1 g/L. Interestingly, the results have also illustrated that the oil-removed EPS had higher ABTS radical scavenging capacity than olive oil-non-removed EPS, 55.67% and 33.88% respectively. Conclusion, this study contributed a novel protocol to extract EPS from O. sinensis fermentation broth