Peracetic acid-based advanced oxidation processes for disinfection: Unveiling mechanism of protein spatial structure disordering

Abstract

Peracetic acid (PAA)-based advanced oxidation processes (AOPs) are promising in wastewater disinfection, but their microbial inactivation capacity and molecular-level disinfection mechanisms are still understudied. This study investigated the inactivation of MS2 bacteriophage (MS2) and Escherichia coli (E. coli) by copper oxide nanoparticles (CuO-NPs)/PAA system, a typical PAA-based AOPs. The inactivation efficacy of MS2 and E. coli was significantly improved, and E. coli regrowth was effectively inhibited in the CuO-NPs/PAA system. PAA-derived reactive oxygen species (ROS) were essential for enhancing inactivation, with acetylperoxy radicals (CH₃C(O)OO) playing a predominant role. PAA-derived ROS intensified the destruction of the external structures of E. coli and the protein capsids and genomes of MS2. This study proposed an innovative molecular-level disinfection mechanism based on protein structural disordering. Amino acids (AAs) degradation experiments and density functional theory (DFT) calculations revealed that AOPs could non-selectively oxidize AAs, potentially disrupting side chain interactions in protein primary structures and consequently altering secondary structures. Fourier-transform infrared spectroscopy (FTIR) analysis supported that the secondary structures of model proteins transformed from α-helices into β-sheets and random coils, indicating spatial structural disordering. Meanwhile, protein function was impaired. This mechanism is potentially essential for microbial inactivation. These insights could deepen the comprehension of the disinfection mechanisms in PAA-based AOPs, facilitating the optimization of disinfection technologies to safeguard the water environment and public health.