Extracellular pH Modulates Intracellular Protein Aggregation to Balance Spray-Drying Resistance and Revival Kinetics of Dormant Lactobacillus bulgaricus

Dormancy can enhance the spray-drying resistance of lactic acid bacteria(LAB), but it can also prolong their revival time during fermentation. There was a close relationship between dormancy and intracellular protein aggregation, and pH was an important factor that affects protein aggregation. This study innovatively elucidates the molecular mechanism by which extracellular pH coordinates the dormancy-metabolism balance in Lactobacillus bulgaricus ( L. bulgaricus )through regulation of intracellular protein aggregation dynamics. This study revealed that subtle environmental pH variations can induce significant reversible transitions in protein aggregation states, exhibiting remarkable pH sensitivity (with a 40-fold difference in solubility between pH 6.0-6.5) and directly influencing industrial performance characteristics. Significantly, quantitative relationships between pH-regulated protein aggregation levels and both cellular stress resistance and metabolic activity were established, thus providing theoretical foundations and practical guidance for developing high-viability probiotic preparations. Furthermore, this study integrated environmental factor regulation, protein conformational changes, and microbial industrial performance into a unified framework, opening new avenues for the industrial application of probiotics.