Saccharomyces cerevisiae inactivation during water disinfection by underwater plasma bubbles: Preferential reactive species production and subcellular mechanisms

The escalating challenges posed by water resource contamination, especially exacerbated by health concerns associated with microbial fungi threats, necessitate advanced disinfection technologies. Within this context, non-thermal plasma generated within bubble column reactors emerges as a promising antifungal strategy. The effects of direct plasma bubbles within different discharge modes and thus-produced plasma activated water (PAW) on the inactivation of Saccharomyces cerevisiae are investigated. Results show that plasma bubbles generated by dielectric barrier discharge (DBD) mode can effectively inactivate yeast cells (∼4.44 logs reduction) within 1 min, outperforming the spark discharge (SD). In this case, SD can cause a significant portion of cell necrosis, possibly due to the high electric field at the bubble interface. In PAW, DBD and SD produce different dominant long-lived oxygen and nitrogen species, while the crucial short-lived species in yeast apoptosis are both attributed to the singlet oxygen (¹O₂) as confirmed by scavenger tests. The detection of intracellular reactive oxygen species and antioxidant enzymes further illustrates the role of PAW in triggering apoptosis. Overall, this study demonstrates the discharge mode-dependent modulation of reactive species chemistry in plasma-liquid interactions and provides new insights into the subcellular mechanism of plasma-enabled yeast inactivation for water resource decontamination.