Reuse of waste casein peptides to capture Cu (II) for long-term antibacterial reutilization

To date, researchers have worked on developing new pathways to control and manage food and industrial wastes (e.g. dairy wastewater, heavy metals, etc.), but most do not involve the reuse of these wastes. Herein, we propose to use casein peptides (CPs) based on dairy waste to capture Cu²⁺ from industrial wastewater, which is reduced to copper and cuprous oxide nanoparticles (consisting of metallic Cu and Cu₂O crystalline phases) distributed on CPs. The prepared product CPs/Cu/Cu₂O NPs showed prominent antibacterial activity against Escherichia coli and Staphylococcus aureus, as well as multidrug-resistant bacteria from livestock wastewater through generating reactive oxygen species (ROS) in combination with released Cu²⁺. The method proposed in this study is also applicable to extract Cu²⁺ from actual electroplating wastewater for bacterial disinfection. Finally, we achieved the modulation of the composition of Cu/Cu₂O NPs loaded on CPs.