A Comprehensive Review on Engineering Lactic Acid Bacteria: Emerging Genetic Tools and Synthetic Biology Strategies

Lactic acid bacteria (LAB) are pivotal in food, pharmaceutical, and environmental applications due to their metabolic versatility and probiotic potential. This review explores the advancements in genetic engineering and synthetic biology strategies to enhance LAB functionality. We examine the genomic architecture of key LAB species, such as Lactobacillus and Lactococcus, highlighting their natural genetic traits and metabolic constraints. Emerging genetic tools, including electroporation, conjugation, and CRISPR-Cas systems, have revolutionized LAB modification, enabling precise gene editing and expression control. Synthetic biology approaches, such as genetic circuits, riboswitches, and biosensor development, offer novel pathways for optimizing LAB for functional foods, mucosal therapeutics, and industrial biotechnology. We discuss applications in probiotic delivery, bioremediation, and agricultural enhancement, emphasizing LAB's role in producing bioactive metabolites and combating pathogens. Challenges, including plasmid instability, metabolic burden, and regulatory hurdles, are addressed alongside socio-ethical considerations for genetically modified LAB. The integration of genome-scale engineering and CRISPR-based technologies holds promise for overcoming these barriers, paving the way for next-generation LAB with enhanced stress tolerance and tailored functionalities. This review synthesizes current knowledge and future prospects, underscoring the transformative potential of engineered LAB in addressing global health, environmental, and industrial needs while navigating biosafety and public perception challenges.