Optimization of enzymatic extraction, characterization and bioactivities of Se-polysaccharides from Se-enriched Lentinus edodes

Selenium (Se) is a necessary micronutrient, while Se-deficiency is common in most areas worldwide. Developing dietary Se-supplements can address this issue. Se-enriched Lentinus edodes are good sources of natural Se-polysaccharides that are promising dietary Se-supplements. However, Se-polysaccharides from Se-enriched Lentinus edodes (Se–P-LE) fruit body via enzymatic-extraction (EE) have only been sparsely studied. Thus, the EE of Se–P-LE was optimized via Box-Behnken and uniform test, and the physicochemical and bio-functional properties of Se–P-LE were investigated herein. The results showed that the optimized EE conditions were: extracting temperature of 45 °C, pH of 4.5, time of 85 min and a liquid-solid ratio of 20:1 mL/g. The addition amount of cellulase, papain and pectinase were 0.80, 0.65 and 0.8 g/100 g samples, respectively. Under this condition, Se–P-LE yield was 18.16 ± 0.10%, and the Se content of Se–P-LE was 29.51 ± 0.23 μg/100 g. Characterization of Se–P-LE showed that Se–P-LE were Se-conjugated polysaccharides with pyranoglycan and β-glycosidic linkages. Se–P-LE were composed of 8 monosaccharides with shear-thinning properties and microcrystalline/amorphous structures. The bioactivities assays showed that Se–P-LE displayed a higher DPPH and hydroxyl radical scavenging rate than ordinary polysaccharides. Besides, Se–P-LE significantly reduced mRNA expression and levels of pro-inflammation factors (NO, IL-6/1β and TNF-α) caused by LPS in RAW264.7 cell line.