Genetic regulation and functional characterization of acid resistance systems in Escherichia coli during fermentation

Microbial survival under acidic conditions is essential for both natural ecosystems and industrial fermentation processes. In Escherichia coli, acid resistance (AR) systems, including the glutamate (Gad), lysine (Cad), and arginine (Adi) decarboxylase pathways, play a crucial role in maintaining pH homeostasis through proton-consuming mechanisms. While these systems have been extensively studied under respiratory conditions, their regulation and activity during anaerobic fermentation remain insufficiently understood, particularly in the context of organic acid production and pH acidification. This project aims to elucidate the activation, gene expression, and enzymatic activity of AR systems under different levels of acid stress during anaerobic fermentation. By integrating fluorescence-based promoter activity analysis, RT-qPCR, and enzymatic assays, the study will provide a comprehensive understanding linking gene regulation to functional output.