Postbiotic polysaccharide and peptide-enriched electrospun nanofibers based on polycaprolactone/ethyl cellulose/sodium alginate as bioactive macromolecular matrices for aflatoxin M1 adsorption in milk

Abstract Aflatoxin M1 (AFM1) contamination in dairy products raises many food safety concerns due to its toxicity and resistance to conventional processes. In this study, a novel bio-based adsorption system was developed using electrospun polycaprolactone/ethyl cellulose/sodium alginate (PCL/EC/SA) nanofibers (NFs) incorporated with postbiotics derived from Lactobacillus rhamnosus . The NFs were fabricated with varying postbiotic loadings (2.5%, 5%, and 10% w/w) and evaluated for AFM1 removal from a real milk matrix at initial concentrations of 100–300 ng/L. The morphological features, surface wettability, and biological compatibility of the NFs were evaluated through Scanning Electron Microscopy (SEM) and Fourier Transform infrared (FTIR) spectroscopy. Subsequently, the capacity of these NFs to absorb aflatoxin M1 from milk samples was determined using HPLC. The highest removal efficiency was achieved with 10% postbiotic-loaded NFs, reaching 88.0%, 91.6%, and 95.5% at AFM1 concentrations of 100, 200, and 300 ng/L, respectively, after 24 h of contact time. The FTIR results supported the incorporation of postbiotic-related functional groups into the nanofiber matrix and revealed enhanced functional group interactions, particularly in hydroxyl, carbonyl, and amide regions. Thermal Gravimetric Analysis (TGA) showed that the presence of postbiotics increased the thermal stability of the composite NFs. Adsorption isotherm analysis revealed that the AFM1 uptake by PCL/EC/SA/Postbiotics NFs followed the Langmuir model, and kinetic studies aligned with a pseudo-second-order mechanism. Furthermore, PCL/EC/SA/Postbiotics NFs sustained an uptake efficiency exceeding 77% over four consecutive cycles. Due to its adsorption performance and reusability, the postbiotic-loaded nanofiber system can be used as an adsorption platform for AFM1 reduction in dairy matrices.