LAUSR

Mixed fermentation with different microorganisms can facilitate fermentation metabolism and increase the low molecular metabolites accumulation, thereby enhancing the bioactive activity. In this study, we evaluated the immune-stimulating activities of Spirulina platensis and different extracts from fermented S. platensis (FS) by mixed probiotics in vitro, by measuring the proliferation and Th1/Th2 immunomodulatory potential on murine primary splenic lymphocytes. The results showed that mixed fermentation enhanced the immunomodulatory activity of S. platensis with higher lymphocyte proliferation compared with non-fermented S. platensis (NFS). Notably, the low molecular weight (<3 kDa) peptide fraction from fermented S. platensis (L-PFS), especially at 40 μg/ml, presented the strongest activity in promoting lymphocytes proliferation and modulating cytokines (IL-2 and IL-10) secretion. Meanwhile, L-PFS enhanced the relative mRNA expression of Th1 cytokine (IFN-γ) and Th2 cytokine (IL-4), along with inhibiting the relative mRNA expression of Th1 cytokines (IL-2 and TNF-α) and Th2 cytokine (IL-10) compared with Concanavalin A-treated lymphocytes. PRACTICAL APPLICATIONS: Fermentation with mixed probiotics could effectively improve the bioactive activity of S. platensis. In particular, L-PFS screened from the FS could significantly contribute to the immune-enhancing activity of lymphocytes, promote the Th1/Th2 balance, and provide insights for the investigation of FS as the potential immunomodulatory food products.