Improvement on the Antioxidant Activity of Polysaccharides by Submerged Fermentation of Shiraia bambusicola GDMCC 60438 (Ascomycota)

Shiraia bambusicola strain GDMCC 60438, originally isolated from eastern China, was applied for production of polysaccharides through submerged fermentation with glucose and potato extracts. Compared with a polysaccharide content of 3.94 ± 0.92% in natural Sh. bambusicola stroma, 9.12 ± 0.36 g intracellular polysaccharides (SIP) could be produced in 100 g freeze-dried Sh. bambusicola mycelium after an optimized fermentation. The SIP showed an 88.65 ± 2.26% hydroxyl radical scavenging activity (HRSA) at the concentration of 4 mg/mL. It was higher than the 31.48 ± 3.12% HRSA of Sh. bambusicola stroma polysaccharide (SSP). In the meantime, a 5 mg/mL SIP showed an equivalent 2,2'-Azino-bis (3-ethylbenzthiazoline-6-sulfonic) acid radical (ABTS+) scavenging activity to ascorbic acid at 0.025 mg/mL. Gel chromatography analysis showed that the SIP had distinct polysaccharide fractions compared with the SSP. Submerged fermentation showed a promising prospect on high production of Sh. bambusicola polysaccharides with improved antioxidant activities.