Factors influencing the inactivation of Bacillus subtilis by epigallocatechin gallate (EGCG)

Abstract

Epigallocatechin gallate (EGCG) is an exceptional plant polyphenol for drinking water disinfection, due to its lasting antibacterial capabilities and broad spectrum of health benefits. Nevertheless, its effectiveness and the underlying mechanisms against chlorine-resistant bacteria, such as Bacillus subtilis, have not been thoroughly explored under various water conditions. The study at hand probed the inactivation rates of EGCG on B. subtilis was subjected to different concentrations, contact times, acidic or basic environments, and temperatures; biological mechanisms were examined by analyzing alkaline phosphatase, proteins, glucose, ATP, and redox biomolecules. Results indicated a positive correlation between EGCG concentration and the inactivation rate of B. subtilis, with the rate notably rising at EGCG levels below 800 mg/l and under acidic pH. The inactivation efficiency increased with temperature increments from 25 to 45 °C. Moreover, EGCG exerted a detrimental impact on the structural integrity, energy metabolism, and the antioxidant defense system of B. subtilis showed a dose-dependent antimicrobial activity against Escherichia coli. Consequently, this study provides a strong foundation for evaluating EGCG's efficacy against chlorine-resistant bacteria, promoting its theoretical application for drinking water treatment and guiding methodological advancements for broader applications.