Advances in Genetic Transformation of Lactic Acid Bacteria: Overcoming Barriers and Enhancing Plasmid Tools

Lactic acid bacteria (LAB) are central to food fermentation, probiotic delivery, and emerging synthetic biology applications, yet their robust cell envelopes and restriction–modification systems complicate DNA uptake. This review synthesizes practical routes for introducing DNA into LAB—natural competence, electroporation, conjugation, phage-mediated transduction, and biolistics—and outlines vector systems for expression and chromosomal editing, including food-grade strategies. We highlight recent advances that broaden strain tractability while noting strain-to-strain variability and host-specific barriers that still require tailored solutions. These advances directly enable applications in food and probiotic biotechnology, including improving starter robustness, tailoring flavor and texture pathways, and installing food-grade traits without residual selection markers. We close with near-term priorities for standardizing protocols, widening replicon compatibility, and leveraging modern genome-editing platforms to accelerate safe, marker-free engineering of industrial and probiotic LAB.