Abstract: Bacillus pumilus, a foodborne pathogen closely associated with food spoilage, can cause food safety issues and substantial financial losses. Thus, developing an effective natural antimicrobial agent is crucial for controlling B. pumilus. Herein, the antimicrobial activity and action mechanism of monogalactosyl monolaurate (MGML) against B. pumilus was investigated. Results showed that the minimum inhibitory concentration (MIC) of MGML was 313 μg/mL. The antimicrobial activity was concentration dependent. MGML caused leakage of intracellular Ca2+ and K+ and ultraviolet (UV)-absorbing materials, indicating altered membrane permeability of B. pumilus cells. According to scanning electron microscopic observation, the surface of bacterial cells became wrinkled and even ruptured with holes in it after treatment with MGML, indicating that the cells were damaged. Analysis of the ultraviolet absorption spectra and the fluorescence quenching spectra suggested that MGML could cause DNA damage and affect its synthesis. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) results showed that MGML also could affect the synthesis of protein. These results suggested that MGML has the potential to be used as a food preservative against B. pumilus.

Key words: monogalactosyl monolaurate, antimicrobial activity, antimicrobial mechanism, Bacillus pumilus, cell membrane damage