d-tryptophan potentiates dielectric barrier discharge cold plasma inactivation of Shewanella baltica through...

Dielectric barrier discharge (DBD) cold plasma combined with d-tryptophan (d-Trp) exhibited a pronounced synergistic inactivation effect against Shewanella baltica, a dominant spoilage bacterium in aquatic products, and the underlying reactive oxygen species (ROS)-mediated mechanism was elucidated. 40 s combined treatment (DBD +d-Trp) achieved a 7.31 log CFU/mL reduction, markedly exceeding the 1.3 log reduction obtained with DBD treatment alone. Physicochemical analysis showed elevated hydrogen peroxide and nitrite levels accompanied by decreased pH in the synergistic system. Electron paramagnetic resonance and radical scavenging assays revealed that d-Trp selectively enhanced singlet oxygen (¹O₂) generation while suppressing hydroxyl radicals and superoxide anions, thereby reshaping the ROS profile compared to DBD treatment alone. Severe cellular damage was observed by scanning electron microscopy, and increased alkaline phosphatase release, potassium leakage, and membrane depolarization confirmed disruption of the cell envelope integrity. Elevated intracellular ROS accumulation and dysregulation of antioxidant enzyme activity indicated aggravated oxidative stress leading to bacterial death. The synergistic inactivation effect was further validated in fish juice, demonstrating superior efficacy compared to individual treatments. These findings demonstrate that d-Trp potentiates plasma inactivation through selective modulation of ROS composition and provide a mechanistic foundation for developing targeted control strategies against specific spoilage bacteria in aquatic products.