Lactic Acid Bacteria as Biofactories: Mechanistic Insights, Engineering Strategies, and Future Horizons for Heterologous Enzyme Expression

Lactic acid bacteria (LAB) constitute a genetically heterogeneous group that is uniquely capable of converting soluble carbohydrates into lactic acid. Such LAB, with a long history of safe consumption in fermented foods, are considered food-grade microorganisms and are highly sought after for a variety of biotechnological applications. Due to their unique properties, LAB can be genetically engineered to produce industrially significant enzymes. LAB act as an expression host for these enzymes by combining already existing engineering systems with techniques such as CRISPR-Cas. This review outlines the progress achieved to date on genome manipulation methods for LAB engineering and future perspectives of genetic tools. These strategies contribute greatly to fully unleashing the potential of LAB, and we further elaborate on how genome editing tools can enhance the capacity of heterologous expression in LAB.