Abstract: In this study, an ethanol-soluble polysaccharide (SLEP) from the dried fruiting bodies of Suillus luteus was prepared by sequential water extraction and ethanol precipitation, rotary evaporation of the ethanol-soluble supernatant for ethanol removal, redissolution in water, dialysis for desalination, and freeze drying. The polysaccharide was structural characterized and its regulatory effect on gut microbial metabolism in tumor-bearing mice was evaluated. The results showed that the molecular mass of SLEP was about 6.2 × 103 Da, and the molar ratio of xylose/palmitic acid/glucose was 1.00:0.03:0.28. SLEP was composed of α-(1→4)-xylopyranose and α-(1→)-glucopyranose as the main chain and branches, respectively. Palmitic acid was covalently bound by ester linkage to SLEP, forming xylan palmitate. Besides, the results of animal experiments showed that intragastric administration of a high dose (200 mg/kg) of SLEP effectively regulated the diversity of gut microbiota in tumor-bearing mice, significantly enhanced the relative abundance of Lactobacillus, activated the bacterial quorum-sensing system, enhanced the immune activity of CD4+ T cells, and inhibited solid tumor growth by 56.35%. This study provides a theoretical basis and data support for developing functional foods with ethanol-soluble polysaccharide conjugates.

Key words: Suillus luteus ethanol-soluble polysaccharide; structural characterization; Lactobacillus; bacterial quorum sensing; CD4+ T cell immunity