Immunomodulatory activity of Alaska pollock hydrolysates obtained by glutamic acid biosensor – Artificial neural network and the identification of its active central fragment

• GLU-ANN was founded for preparing the target pollock hydrolysates (PFH).
• PFH enhances the humoral immunity, cellular immunity and non-specific immune function.
• Mechanism of PFH is through direct up-regulation of IL-2 IL-4 and IL-6 gene expression.
• The active central fragment was purified and identified as PTGADY.
• PFH can act as a potent immunomodulator.

The glutamic acid biosensor and artificial neural network (GLU-ANN) was employed to monitor the hydrolysis of Alaska pollock protein for production of immunomodulatory peptides. The relative error of GLU-ANN was in the range of 0.23% to 2.81%. The target pollock hydrolysates (PFH) were prepared using GLU-ANN, which significantly enhanced humoral, cellular, and non-specific immunity in immunosuppressed mice, induced by hydrogenated cortisone (p < 0.05). In addition, treatment with PFH significantly increased the production of interleukin (IL)-2, IL-4, and IL-6 in immunosuppressed mice (p < 0.05), while interferon-gamma (IFN-γ) showed no significant change. The active central fragment that exhibited the highest lymphocyte proliferation rates was further purified using ion exchange chromatography, gel filtration chromatography, and reversed-phase high performance liquid chromatography (RP-HPLC). The amino acid sequence of this fragment was as follows: Pro-Thr-Gly-Ala-Asp-Tyr (PTGADY). Therefore, PFH shows promise as a potent immunomodulator with potential applications in functional food.