A low-molecular-weight α-glucan PPS2-A derived from potato starch fermentation by Antarctic Penicillium chrysogenum MS-02: Structural characterization and immunomodulatory activity.

Glucan, a potent immunomodulator with well-established pharmacological activities, can be efficiently produced through the microbial transformation of low-value substrates. Here, the psychrotolerant Antarctic fungus Penicillium chrysogenum MS-02 was cultivated on potato starch. A homogeneous glucan with molecular weight 1.293 × 104 Da (termed PPS2-A) was then isolated from the fermentation broth using gel-filtration and ion-exchange chromatography. Structural characterization revealed that PPS2-A featured a linear backbone composed of (1 → 4)-linked α-d-glucopyranosyl (Glcp) residues, with α-(1 → 4)-linked Glcp side chains at C-6 positions, and lacked a triple-helical conformation. Studies on primary mouse immune cells demonstrated that PPS2-A significantly enhanced splenic lymphocyte proliferation, potentiated peritoneal macrophage phagocytic capacity, and upregulated NO secretion and acid phosphatase activity. Moreover, PPS2-A enhanced proliferation and phagocytosis, suppressed apoptosis, and promoted M1 polarization (elevated NO, cytokines TNF-α/IL-1β/IL-6, and CD86+). Collectively, these findings demonstrate the immunostimulatory potential of PPS2-A as a pro-inflammatory macrophage activator, and support its development as a candidate natural immunomodulator derived from the Antarctic fungus.