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)-alpha-glucan structure was dominant in the two neutral polysaccharides, whereas the (1 -> 6)-beta-glucan was dominant in the two acidic polysaccharides. Hot-air drying could thus promote the alpha-configuration in neutral polysaccharides while reducing the beta-configuration in acidic polysaccharides. FLEP-1, FLEP-2, HLEP-1 and HLEP-2 had potential scavenging capacity against the ABTS center dot(+), 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-alpha 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. (C) 2019 Published by Elsevier B.V.