Effects of freeze drying and hot-air drying on the physicochemical properties and bioactivities of polysaccharides from Lentinula edodes.

Fresh Lentinula edodes were dried using two process technologies-freeze drying (FD) and hot-air drying (HD). The physicochemical, antioxidant and immunomodulatory properties of purified polysaccharides from dried L. edodes (LEP) were then comparatively investigated. Two neutral polysaccharides (FLEP-1 and HLEP-1) and two acidic polysaccharides (FLEP-2 and HLEP-2) were obtained by DEAE-52 cellulose column. The HD treated LEP had higher levels of uronic acid than that of the FD treated LEP. The molar ratios of monosaccharides in FLEP-1, FLEP-2, HLEP-1 and HLEP-2 were different. Moreover, HD treated LEP had more galactose and less glucose. The (1 → 3)-α-glucan structure was dominant in the two neutral polysaccharides, whereas the (1 → 6)-β-glucan was dominant in the two acidic polysaccharides. Hot-air drying could thus promote the α-configuration in neutral polysaccharides while reducing the β-configuration in acidic polysaccharides. FLEP-1, FLEP-2, HLEP-1 and HLEP-2 had potential scavenging capacity against the ABTS+, whereas freeze-dried polysaccharides exhibited a stronger scavenging ability than that of hot-air dried polysaccharide. LEP could improve immunity by inducing the secretions of NO, TNF-α and IL-6, whereas hot-air drying improved the immunomodulatory activity of LEP. Our results suggested that freeze drying and hot air drying could be appropriately used to obtain functional polysaccharides from L. edodes.