Pleurotus eryngii (PE) has been sought after for its various health benefits and high content of phenolic compounds. This study explored the feasibility of steam explosion (SE)-assisted extraction of polysaccharides with high antioxidant capacities from PE. An orthogonal experimental design (OED) was used to optimize the SE-assisted extraction of PE. The influence of the optimized SE-assisted extraction on the physicochemical properties of PE polysaccharides was determined by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), monosaccharide compositional analysis and antioxidant capacity assays. Under optimal SE conditions, SE-assisted extraction increased the polysaccharide yield by 138% compared to extraction without SE-assistance. In addition, SEM demonstrated that SE-assisted extraction markedly altered the spatial structure of Pleurotus eryngii polysaccharides (PEP), and monosaccharide compositional analysis revealed that this pretreatment significantly increased the proportions of some monosaccharides, such as glucose, rhamnose and arabinose, in the isolated PEP. FTIR spectra indicated no change in the major chemical functional groups of PEP. PEP extracted by SE-assisted extraction had significantly increased free radical scavenging and antioxidant capacities. In conclusion, SE-assisted extraction appears to be a novel polysaccharide extraction technology, which markedly increases extraction yields and efficiency and can increase the biological activity of polysaccharide extracts.

Staphylococcus aureus is a major foodborne pathogen that poses persistent challenges to food safety. Antimicrobial photodynamic treatment (PDT) has emerged as a promising non-thermal antimicrobial strategy capable of effectively inactivating S. aureus, though accumulating evidence suggests that the bacteria may initiate adaptive responses to the PDT or even develop tolerance. However, the metabolic mechanisms underlying bacterial responses to PDT exposure, particularly under sub-lethal conditions, remain poorly understood. Thus, in the current study, untargeted metabolomics based on liquid chromatography–tandem mass spectrometry (LC–MS/MS) and gas chromatography–mass spectrometry (GC–MS) were employed to characterize intracellular metabolic alterations in S. aureus following curcumin-mediated PDT (40 µM curcumin, 425 nm blue light at intensity of 0.198 J cm⁻²). The obtained results revealed a clear separation between the control and PDT-treated groups, indicating sub-lethal PDT induced pronounced metabolic perturbations while preserving partial cellular viability. A total of 97 significantly differential metabolites were identified, encompassing a range of key metabolites associated with amino acid biosynthesis, lipid metabolism, and nucleotide metabolism, indicating the PDT-induced metabolic alterations in pathways could be associated with stress adaptation, membrane integrity, and energy metabolism. Collectively, these findings demonstrate that PDT, even at sub-lethal doses, induces extensive metabolic dysregulation in S. aureus, which potentially represent critical bactericidal vulnerability points target by PDT, yet may paradoxically participate in adaptive metabolic responses that support bacterial survival under PDT exposure. Further investigations are therefore warranted to elucidate the relationships among PDT-induced metabolic perturbations, bacterial inactivation, and long-term phenotypic adaptation. Overall, this work may provide mechanistic insight into PDT-induced antimicrobial action and support further optimization of PDT as an effective non-thermal intervention for food safety and preservation.