Quality features and immunomodulatory activity of transglutaminase-modified bovine-soy milk fermented by Lactiplantibacillus plantarum AHQ-14

Abstract Fermented dairy products are gradually gaining more attention as functional foods with potential immune-related benefits, but mixed protein systems still face challenges in maintaining stable structure and biological activity. In this study, Lactiplantibacillus plantarum AHQ-14, a probiotic with good proteolytic ability, and transglutaminase (TG) were used to ferment and modify bovine-soy milk, and their effect on the texture properties and potential immunomodulatory function of the corresponding product were evaluated. The results indicated that TG modification compensated for the quality shortcomings of the fermented milk produced by single probiotic. In vitro experiments demonstrated that the fermented bovine-soy milk prepared by L. plantarum AHQ-14 combined with TG (AT group) modulated macrophage responses and increased the production of IL-1β, TNF-α, and NO. Furthermore, in vivo experiments with cyclophosphamide-induced immunosuppressed mice showed that the AT group alleviated immune organ damage, promoted splenic lymphocyte proliferation, partially restored serum cytokine and immunoglobulin levels, and rebalanced the intestinal microbiota composition. These findings suggest that the fermented bovine-soy milk prepared with L. plantarum AHQ-14 and TG may serve as a candidate functional fermented product with immunomodulatory potential.