Preparation of copper sulfate/natamycin/carboxymethylcellulose/agar film for synergistic antibacterial application in fruit via causing cuproptosis of Escherichia coli O157: H7

This study has investigated cuproptosis caused by copper sulfate (CuSO 4 ) in Escherichia coli O157: H7 and its mechanism. Meanwhile, the mechanism of CuSO 4 combined with natamycin (Nata) against E. coli O157: H7 planktonic and biofilm cells were also investigated. Finally, we prepared an agar-based film, researched its properties, and used it for packaging cherry tomatoes and purple kale. The results indicated that CuSO 4 could cause cuproptosis in E. coli O157: H7 and lead the genes related to Fe-S cluster protein ( hyfA , sufB , xdhC , and narY ) to down-regulate and cuproptosis-related proteins to change. Then, CuSO 4 combined with Nata could synergistically decrease E. coli O157: H7 bacterial counts in planktonic condition and biofilm by synergistically affecting the membrane potential, cytoplasm leakage, permeability of outer membrane and inner membrane. After that, CuSO 4 and Nata could change the mechanical properties, color and optical characteristics of agar-based film, and decrease the water vapor permeability and oxygen permeability value. Finally, CuSO 4 @Nata@Carboxymethylcellulose@Agar film effectively lowered the counts of E. coli O157: H7 in cherry tomatoes and purple kale during the storage.