Electrospun Casein fibers obtained from revalued milk with mechanical and antibacterial properties

The present study describes the harnessing of revalued cow milk (denoted as waste milk) for fabricating casein fibers (CAS) with enhanced mechanical performance and antibacterial properties by the electrospinning method. For this purpose, polyethylene oxide (PEO) was employed (10 and 20 wt%) as a binder for the appropriate electrospun CAS fibers. Different amount of tannic acid (TA) was incorporated into casein/polyethylene oxide fibers (CAS/PEO) as a crosslinker agent, bringing filaments with a diameter of ca. 2 µm. The incorporation of 4 wt% of TA promotes the fibers' reticulation, forming a stable three-dimensional network. Also, the mechanical performance of CAS/PEO fibers was improved, where the tensile strength was increased from 0.91 MPa to 1.88 MPa with 4 % of TA, while the breaking elongation was increased from 93.74 % to 274.56 %. This behavior benefits the processing of fibers by electrospinning. Furthermore, the TA addition during the electrospun of CAS/PEO fibers enhances fibers' wettability properties and thermal stability induced by the crosslinker agent. Additionally, the antibacterial activity (AA) test demonstrates that CAS fibers can inhibit the growth of Gram-positive S. aureus and Gram-negative E. coli after 0.5 h, 1.5 h, 3 h, and 24 h of contact, which is generated by the TA addition. Our results suggest that the electrospun fabrication of CAS/PEO fibers with TA as a crosslinker agent represents an innovative harnessing of waste milk to produce functional textiles with potential biological application.