Microalgal Nanofactory: Green Synthesis of Zinc Oxide Nanoparticles and Their Antibacterial and Antioxidant Potentials

Microalgal nanofactories are a new era of using green microalgae for the synthesis of materials and molecules with commercial viability. Unlike other modes of synthesis, uses bacteria, fungi, plant extract, and biomolecules and claims an eco-friendly and green synthesis approach. On the other hand, the synthesis of materials adopting green microalgae gained huge attention for the exploration and zero wastage and absolute eco-friendly approach. In this study, Chlorella vulgaris is used for the synthesis of zinc oxide nanoparticles (ZnO NPs) from zinc chloride as a precursor by bioreduction process. The biofabricated ZnO NPs were characterized by using UV–Vis spectroscopy, Fourier transform infrared spectroscopy (FT-IR), transmission electron microscope (TEM), X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDAX), dynamic light scattering (DLS), and zeta potential which showed the hexagonal nanoparticles with an average size of 54.11 ± 4.98 nm. The ZnO NPs exhibited antibacterial activity against the Gram-negative bacteria Escherichia coli and Klebsiella pneumoniae, and the Gram-positive bacteria Bacillus subtilis and Staphylococcus aureus, as confirmed by a zone of inhibition assay. It possesses a potent antibacterial activity against all the test organisms and a higher rate of inhibition was observed in Gram-negative bacteria than that of Gram-positive bacteria. The free radical scavenging activity of biofabricated ZnO NPs showed at the maximum when compared with the algal extract. This finding comprehended a cost-effective and eco-friendly ZnO NP synthesis along with their application as an alternative and effective antibacterial agent owing to their enhanced antioxidant potential by using microalgal nanofactory.