From brewery waste to bioactive nanomaterials: Eco-friendly biosynthesis of silver nanoparticles with antimicrobial and anticancer activities using brewery waste-cultivated Parachlorella kessleri

Green algae have emerged as promising platform for the eco-friendly biosynthesis of nanoparticles owing to their abundance in proteins, pigments, polysaccharides, phenolic compounds, and other bioactive metabolites. The present study aimed to synthesize silver nanoparticles (Pk-AgNPs) using the biomass of the green alga Parachlorella kessleri MDC6524 cultivated on brewery production waste and to evaluate their antimicrobial and antiproliferative activities. The algal biomass served as a natural reducing and stabilizing agent during Pk-AgNPs synthesis under illumination. UV-Vis spectroscopy revealed a characteristic surface plasmon resonance peak at 440 nm, confirming Pk-AgNPs formation. Transmission electron microscopy showed predominantly ellipsoidal Pk-AgNPs with an average size of 46 nm, while X-ray diffraction analysis confirmed their crystalline structure and purity. Fourier-Transform Infrared spectroscopy indicated the involvement of functional groups from P. kessleri biomass in AgNPs formation. Pk-AgNPs exhibited significant antibacterial activity against Staphylococcus aureus, Enterococcus hirae , Salmonella typhimurium, and Pseudomonas aeruginosa , with minimum inhibitory concentration (MIC) values ranging from 10 to 20 μg mL −1 , and greater activity against Gram-negative bacteria. Their antifungal activity against Aspergillus flavus, Penicillium aurantioviolaceum, and Trichoderma viride was species-dependent, with MIC values ranging from 200 to 500 μg mL −1 . Furthermore, Pk-AgNPs exhibited dose- and time-dependent cytotoxicity against lung adenocarcinoma A549 cells at low concentrations (0.6–10 μg mL −1 ). These findings demonstrate the potential of brewery waste-derived algal biomass as a renewable platform for nanoparticles biosynthesis and suggest that the resulting Pk-AgNPs possess promising antimicrobial and anticancer properties.