Structure and Bioactivity of Intracellular and Extracellular Polysaccharides of Trametes lactinea Mycelium

Trametes lactinea polysaccharides have a high medicinal value; however, we still know little about the structure and bioactivity of intracellular and extracellular polysaccharides in the mycelial liquid fermentation of T. lactinea. This study analyzed the structures of intracellular (IP-1, IP-2, and IP-3) and extracellular (EP-1 and EP-2) polysaccharide components isolated from T. lactinea liquid fermentation, as well as investigated their antioxidant, antibacterial, and immunomodulatory properties. The results showed that IP-3 was the only component with a triple-helix structure, while the other four components did not possess this structure. IP3 has a higher molecular weight, flavonoid, and total phenolic content compared to other components. Both intracellular and extracellular polysaccharide components exhibited strong scavenging abilities against ABTS and DPPH radicals. The components showed limited antibacterial effects against four types of bacteria (Staphylococcus aureus, Bacillus subtilis, Erwinia carotovora, and Escherichia coli), and were found to be non-toxic to RAW264.7 cells, even promoting cell proliferation. Furthermore, within a specific concentration range, all components enhanced the phagocytic activity of RAW264.7 cells, increased the secretion of NO, TNF-α, and IL-6, and demonstrated concentration-dependent effects, with IP-3 displaying the most potent immunomodulatory activity. This study shows a high potential for the development and utilization of polysaccharides derived from the liquid fermentation of T. lactinea mycelium.