Antibacterial effect of Cu₂O/TiO₂ photocatalytic composite on Pseudomonas marginalis pv. marginalis

Cu₂O/TiO₂ visible-light photocatalytic composite was successfully synthesized by supercritical solvothermal route. Cu₂O/TiO₂ presented excellent bacterial inactivation activity for Pseudomonas marginalis pv. marginalis, which was related to the concentration of bacteria and the antibacterial time. The highest sterilization ratio reached up to 100% when the bacteria was treated with 80 μg/mL of Cu₂O/TiO₂ photocatalytic composite for 80 min, which could be further proved by the damage of integrity and shrink of the cell membrane in transmission electron microscopy (TEM) image. When the bacterial concentration was 1 × 10⁵ CFU/mL, the minimum inhibitory concentration (MIC) and the minimum bactericidal concentration (MBC) were determined as 16 and 32 μg/mL by agar dilution, respectively. Meanwhile, the production of reactive oxygen species (ROS), glutathione reductase (GR) and glutathione (GSH) of Pseudomonas marginalis pv. marginalis treated by Cu₂O/TiO₂ were determined by DCFH-DA, DTNB and kinetic method, respectively, to evaluate the anti-oxidation capacity of bacteria cell. The enzyme activity of peroxidase (POD), superoxide dismutase (SOD), and catalase (CAT) in bacteria treated with Cu₂O/TiO₂ were measured to further confirm the overproduction of ROS. Cu₂O/TiO₂ was demonstrated as the excellent visible-light photocatalyst for efficiently killing Pseudomonas marginalis pv. marginalis with the low dosage. Finally, the Cu₂O/TiO₂ composite photocatalytic material was applied to cucumber seedlings based on field experimental, and its inhibitory effect in practical application was judged by measuring the morphology, enzyme activity and resistance index of cucumber plants. It is of great significance to the practical application as a suitable and powerful antibacterial agent for Pseudomonas marginalis pv. marginalis and other bacteria.