Unlocking Casein Bioactivity: Lactic Acid Bacteria and Molecular Strategies for Peptide Release.

Bioactive peptides encrypted in bovine β-casein display diverse physiological functions, including antihypertensive, antioxidative, antimicrobial, and immunomodulatory activities. These peptides are normally released during gastrointestinal digestion or microbial fermentation, especially by proteolytic systems of lactic acid bacteria (LAB). However, peptide yields vary widely among LAB strains, reflecting strain-specific protease repertoires. To overcome these limitations, the scientific goal of this study is to provide a comprehensive synthesis of how synthetic biology, molecular biotechnology, and systems-level approaches can be leveraged to enhance the targeted discovery and production of β-casein-derived bioactive peptides. Genome engineering tools such as clustered regularly interspaced short palindromic repeats associated system (CRISPR/Cas) systems have been applied to modulate gene expression and metabolic flux in LAB, while inducible expression platforms allow on-demand peptide production. Additionally, cell-free systems based on LAB lysates further provide rapid prototyping for high-throughput screening. Finally, multi-omics approaches, including genomics, transcriptomics, proteomics, and metabolomics, further help pinpoint regulatory bottlenecks and facilitate rational strain optimization. This review provides a comprehensive overview of bioactive peptides derived from bovine β-casein and highlights recent progress in LAB-based strategies-both natural and engineered-for their efficient release. These advances pave the way for developing next-generation functional fermented foods enriched with targeted bioactivities.