Comparison of immunomodulatory activity of polysaccharides and soluble dietary fibers and adsorption capacities of insoluble dietary fibers extracted from Lentinus edodes stipes

Stipes are the major waste from the processing of Lentinus edodes . To make full use of L. edodes stipes (LES), different fractions of LES polysaccharides (LESPs) were first obtained by water extraction and gradient ethanol precipitation. Afterwards, the LES residues were treated with an optimal combination of Aspergillus niger and Saccharomyces cerevisiae for the preparation of soluble/insoluble dietary fibers (LESS/LESI) using the response surface methodology and the Box-Behnken design. Subsequently, the in vitro immunomodulatory activity of LESPs and LESS, as well as the adsorption capacities of LESI were evaluated. The results showed that LESPs were neutral polysaccharides, mainly containing glucose. The optimal parameters for modifying the residues of LES were the followings: 4% ( w / w ) A. niger , 8% ( w / w ) S. cerevisiae , 31 ℃, 3 d, and a solid–liquid ratio of 1:12.5 in a yield of 14.73%/82.45% of LESS/LESI, respectively. The in vitro immunomodulatory activity assays revealed that LESPs and LESS had potent immunostimulatory activity to increase phagocytosis, acid phosphatase activity and nitric oxide production of RAW264.7 murine cell macrophages. The evaluation of adsorption capacities revealed that LESI owned stronger water holding capacity, oil holding capacity and water swelling capacity. This research could provide an effective way to fully utilize discarded L. edodes stipes with high added-value. Graphical Abstract An effective strategy was built to fully utilize discarded L. edodes stipes by preparing polysaccharides (LESPs-20, LESPs-50 and LESPs-80), soluble and insoluble dietary fibers (LESS/LESI). Their products showed immunomodulatory activity and adsorption capacities.