Antibacterial Mechanism of Rhamnolipids against Bacillus cereus and Its Application in Fresh Wet Noodles

Abstract

Bacillus cereus (B. cereus) is a common foodborne pathogen causing food poisoning incidents. This study aimed to evaluate the antibacterial activity and underlying mechanism of rhamnolipids (RLs) against B. cereus. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of RLs for B. cereus were determined to be 16.0 mg/L and 32.0 mg/L, respectively. Scanning electron microscopy and fluorescence microscope images, as well as data of membrane potential, relative electric conductivity, and leakage of intracellular components revealed that RLs disrupted the integrity of the cell membrane. Furthermore, the reactive oxygen species content, catalase (CAT) and superoxide dismutase (SOD) activity indicated that RLs activated the oxidative stress response of B. cereus in response to RLs. Fresh wet noodles (FWN) were used as a food model, and RLs showed a significant killing effect on B. cereus with a sustained inhibitory effect at the concentrations ranging from 128.0 to 1024.0 mg/kg. Additionally, RLs promoted the conversion of free water to bound water in FWN, which improved the storage of FWN and made the taste more resilient and chewy. These results suggest that RLs could be a potential alternative to antimicrobial agents and preservatives for applications in food processing.