Fractionation, characterization, and assessment of nutritional and immunostimulatory protein-rich polysaccharide-protein complexes isolated from Lentinula edodes mushroom

This study aimed to fractionate and characterize the protein-rich polysaccharide-protein (PSP) complexes from a well-known edible mushroom, Lentinula edodes, and assess their nutritional and immunostimulatory properties. Crude PSP isolated from the mushroom water extract was purified by anion exchange chromatography, yielding fractions PSP-F1 and PSP-F2 containing 66.1 % and 74.0 % protein, respectively. Both fractions exhibited primarily β-sheet and random-coil protein structures, though the crude PSP fraction exhibited an additional α-helix structure. On SDS-PAGE, PSP-F1 showed two molecular weight bands, one below 10 kDa and another at 34 kDa, and PSP-F2 showed several bands, one below 10 kDa and others between 34 and 95 kDa. The nutritional value of essential and non-essential amino acid profiles was in the order of PSP-F2 > PSP-F1 > crude PSP; the amino acid ratio coefficient values of the crude PSP, PSP-F1, and PSP-F2 were 63 %, 67 %, and 72 %, respectively. The combination of PS and PSP fractions exhibited stronger immunoactivity than PSP-F1 or PSP-F2 alone. PSP-F2 showed a higher immunostimulatory activity than PSP-F1 in RAW264.7 cell culture. PSP-F2 was also more abundant of easily absorbed high-quality proteins. The results provide useful references for dietary and medicinal uses of PSP fractions in L. edodes and other edible mushrooms.