Investigation of Prebiotic Activity and Oxidative Damage Protection for Exopolysaccharides Derived from Liquid Fermented Poria cocos

Poria cocos is a traditional Chinese medicinal and edible fungus. Poria cocos polysaccharides possess biological activities such as antioxidant and anti-inflammatory effects, making them a novel resource for functional foods. To promote the industrial application of Poria cocos polysaccharides in functional foods, this study utilized liquid fermentation technology to prepare Poria cocos exopolysaccharides (PCE) and compared them with Poria cocos fruiting body polysaccharides (PCP) in terms of intestinal microbiota regulation and in vivo oxidative damage protection. The results showed that PCE contained (53.98 ± 0.19)% of total sugars as well as (6.64 ± 0.51)% of proteins. Two fractions (PCE-0 and PCE-0.2) were obtained by purification of PCE, which had smooth clustered and rough flaky microscopic morphology, respectively. Both of them were composed of glucose, mannose, galactose and other monosaccharides, with β-glycosidic bonds and higher branched structures. PCE-0 contained a triple helical structure while PCE-0.2 did not. In vivo results showed that PCE increased the abundance of probiotics such as Bacteroides, Oscillospira, and Akkermansia in the mouse intestine, exerting a positive influence on maintaining intestinal homeostasis. Additionally, PCE effectively enhanced the activity of superoxide dismutase and glutathione peroxidase in the serum, liver and jejunum of oxidative-damaged mice. It also reduced malondialdehyde content, improved total antioxidant capacity, and regulated the levels of IL-1β, IL-6, IL-10, TNF-α. These effects protected the mice against oxidative damage and inflammation caused by alcohol-induced liver injury. Further molecular mechanism studies suggest that PCE alleviates alcohol-induced liver injury through activation of the Keap1/Nrf2 signaling pathway. This study aimed to explore the potential application of liquid fermented Poria cocos polysaccharides in functional foods, providing a reference for the development and utilization of liquid fermentation products from edible fungi.