Electrochemical identification of riboflavin-mediated redox adaptation in Escherichia coli under mild heat stress.

Understanding the stress response mechanisms of Escherichia coli (E. coli) is essential for controlling its contamination in food systems. In this study, the adaptive response of E. coli to mild heat treatment (MHT) was investigated from an electrochemical perspective, with a focus on energy metabolism and electron transport processes. A distinct oxidation peak at -0.45 V (vs Ag/AgCl) was identified and attributed to riboflavin (RF) through differential pulse voltammetry (DPV), HPLC, and LC-MS/MS analyses. Under MHT condition, the RF-associated electrochemical signal was significantly enhanced. Combined with colony counting and morphological observations, this increase was confirmed to originate from stress-induced metabolic adaptation rather than cell death. This conclusion was further supported by altered intracellular ATP and ROS levels. Transcriptomic analysis revealed upregulation of RF biosynthesis genes (ribA, ribD, ybjI, ribE) and related energy metabolic pathways. ribA knockout demonstrated that RF-deficient mutants failed to survive under heat stress without exogenous RF supplementation. Overall, this study provides novel electrochemical insights into the metabolic mechanisms underlying bacterial adaptation to MHT and identifies RF-mediated redox regulation, particularly ribA, as a potential target for antimicrobial control in food processing.