Effect of Enzymatic Glycosylation on Film-Processing Properties and Biological Activities of Black Soybean Protein

In this study, chitooligosaccharides (COS) were introduced into black soybean protein (BSP) using transglutaminase (TG) as a biocatalyst. The film-processing properties and physiological activities of the enzymatically glycosylated black soybean protein (EGBSP) were studied. The results showed that glycosylation decreased the surface hydrophobicity, absolute value of the zeta potential, its minimum solubility, and film permeability of BSP by 69.86%, 6.04%, 36.68%, and 14.91%, respectively, while increasing the tensile strength and elongation at break of its protein film by 56.57% and 172.68%, respectively. The gel time was shortened, and the acid-induced gel properties of EGBSP were similar to those of BSP. The anticancer effect of EGBSP was evaluated by the tumor inhibition rate, flow cytometry, and morphology observation of an ascites tumor in H₂₂ tumor-bearing mice. The immune organs (spleen, thymus), immune cells (lymphocytes, NK cells), and immune factors (IL-2, IL-12) of H₂₂ tumor-bearing mice were detected to evaluate the immunomodulatory effects of EGBSP. The results showed that medium and high doses of BSP had positive effects on immune enhancement and anti-cancer activity of H₂₂ tumor-bearing mice, while almost all doses of EGBSP showed significant effects. These results indicated that glycosylation significantly improved the anti-cancer effect and immunomodulatory activity of H₂₂ tumor-bearing mice while prolonging their overall survival. In conclusion, the glycosylation method using microbial transglutaminase to catalyze the introduction of chitooligosaccharides into black bean protein can improve the film-processing properties and biological activities of BSP more effectively than the enzyme crosslinking method.