Prebiotic Potential of Whey Protein Conjugate/Anthocyanin Nanoparticles: in vitro Fermentation and Gut Microbiota Modulation.

It remains a challenge to clarify the selective utilization of anthocyanins (ANs) for gut microbiota modulation mediated by whey protein conjugate carriers, thereby enhancing their prebiotic efficacy. In this study, structural characteristics of whey protein conjugate/anthocyanin nanoparticles (WPC_D_ANs) were systematically characterized. Furthermore, their microbial fermentation properties and effects on gut microbiota composition were analyzed via in vitro pure probiotic cultures and mixed fecal microbiota fermentation. Results showed that incorporation of ANs significantly enhanced WPC_D's UV–Vis absorption and chromophore exposure. With hydrogen bonds and hydrophobic interactions as the main driving forces, the microstructure became denser. In pure cultures, WPC_D_ANs promoted the proliferation of Lactobacillus rhamnosus, Lactobacillus plantarum, and Lactobacillus fermentum more effectively than free ANs, equivalent to the positive control (FOS) at the same concentration; it also significantly reduced system pH and inhibited Staphylococcus aureus and Escherichia coli. In vitro fecal fermentation confirmed that WPC_D_ANs regulated gut microbiota diversity and composition, increased the relative abundance of beneficial bacteria (e.g., Lactobacillus, Bifidobacterium), promoted short-chain fatty acid (SCFAs) production (especially butyric and hexanoic acids), and exhibited superior DPPH radical scavenging activity (most notable at 8–12 h of fermentation). In conclusion, WPC_D_ANs exhibit prebiotic potential, effectively modulate the gut microbiota, and promote SCFAs production, thereby providing new insights and a scientific basis for developing gut health-oriented functional foods.