Sour whey-derived carbon dots; synthesis, characterization, antioxidant activity and antimicrobial performance on foodborne pathogens

Zero-dimensional carbon nanomaterials, known as carbon dots (CDs), have become increasingly popular as nanostructures for food preservation due to their antimicrobial and antioxidant properties. In this study, heteroatom-doped CDs were effectively synthesized from sour whey using a hydrothermal method. The size, chemical, and structural composition, as well as the optical and spectral properties of the synthesized CDs, were thoroughly characterized. Furthermore, this study also investigated the antimicrobial, antioxidant, and cytotoxic properties of CDs. Semi-spherical N- and P-doped CDs with size less than 7.8 nm were synthesized. The results of the cytotoxicity test suggested that CDs are low-toxic nanomaterial. The susceptibility of Salmonella Typhimurium was found to be higher than that of Listeria monocytogenes, with a minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 500 μL/mL and 1000 μL/mL, respectively. Based on SEM observations, it was observed that CDs derived from whey mainly targeted the bacterial cell wall. In the modeling of antimicrobial kinetics, the Weibull model provided a strong fit (R2 > 0.9), particularly for the inactivation kinetics of S. Typhimurium. CDs produced from abundant sour whey, which is a sustainable, inexpensive, and eco-friendly source, exhibited important characteristics such as low cytotoxicity and antimicrobial capabilities. The synthesized CDs have potential as antimicrobial or antioxidant agents in food formulations, as well as UV-blockers and nanofillers in the development of composite polymers for food packaging.