Quantification of β-Glucan from Culinary-Medicinal Mushrooms Using Novel Artificial β-Glucan Recognition Protein

(1->3)-β-D-glucans (BGs), found in culinary-medicinal mushrooms, exhibit an immunostimulatory effect; hence, it is important to measure the content of BGs contained in mushrooms. BGs content in a mushroom extract was measured using a recombinant BG-binding protein, supBGRP, and compared with the existing BG assay using BGs antibody. The specificity of supBGRP enzyme immunoassay (EIA) was evaluated using a commercially available polysaccharide reagent. The supBGRP did not react to barley glucan, dextran, mannan, pustulan, and xylan, but reacted to sonifilan, and only slightly to curdlan. Among the BGs tested, supBGRP was most reactive to lentinan. The glucans were extracted using hot water and alkaline solution from the fruit body of the following edible mushrooms: Pleurotus ostreatus, Grifola frondosa, Lentinus edodes, Hypsizygus marmoreus, Flammulina velutipes, and Auricularia polytricha. All BGs extracted from edible mushrooms were detectable; in particular, the reactivity of supBGRP toward the alkaline-extracted fraction from Lentinus edodes was higher than that toward polyclonal antibody for BGs. The results suggest that supBGRP had a specific reaction to BG. The supBGRP seems to be superior to antibodies due to easy availability as a reagent and stability as a protein molecule for measurement of BGs.