Mechanisms of Lactic Acid Bacteria Adaptation to Acidic Environments: The Possible Interplay between Two-Component System (TCS) and γ-Aminobutyric Acid (GABA) Production

This review analyzes the mechanisms by which lactic acid bacteria (LAB) adapt to acidic environments, with a particular focus on the potential linkage between the two-component system (TCS) and γ-aminobutyric acid (GABA) production. LAB acidify their surroundings by producing lactic acid during fermentation, and as probiotics, they must also survive the highly acidic conditions of the human gastrointestinal tract. Consequently, they have developed sophisticated acid adaptation systems. At the molecular level, this review examines how LAB respond to acid stress, demonstrating that TCS plays a crucial role in sensing environmental signals and regulating gene expression accordingly. Additionally, the review explores the mechanisms through which GABA, produced as part of the acid stress response, contributes to acid tolerance. The findings suggest a potential connection between TCS signaling pathways and GABA production, which provides a fundamental basis for developing new strategies to enhance GABA production in LAB. From an industrial perspective, modulating TCS signaling could help optimize fermentation processes and improve probiotic viability. Furthermore, this review provides a theoretical basis for developing LAB strains with enhanced acid resistance and increased GABA productivity.