Inactivating Bacillus cereus spores with pulsed light: roles of thermal and reactive oxygen species-mediated mechanisms.

Bacillus cereus (B. cereus) is a foodborne pathogen known for its highly resistant spores, posing a significant challenge to food safety. This study investigates the inactivation of B. cereus spores by pulsed light treatment and explores the underlying mechanisms. Optimal treatment conditions were determined as 215 J emission energy, 10 cm irradiation distance, and 50 s flash duration, achieving 3.10 log CFU/mL spore inactivation. Effect-elimination experiments revealed that both thermal effects and reactive oxygen species (ROS) significantly contributed to spore inactivation. Analysis of surface properties, resistance, germination behavior, and intracellular structural changes demonstrated that pulsed light treatment disrupted spore integrity. As a result, spores exhibited lower surface hydrophobicity, increased leakage of proteins and metal ions, and reduced resistance to acidic conditions and sodium hypochlorite. Raman spectroscopy and transmission electron microscopy confirmed severe damage to spore proteins and DNA, while dipicolinic acid leakage remained minimal. These results highlight the potential of pulsed light as an effective non-thermal sterilization method for spore inactivation, with ROS and thermal effects playing key roles in the process.