Advanced Nanoenabled Microalgae Systems: Integrating Oxidative Stress-Induced Metabolic Reprogramming and Enhanced Lipid Biosynthesis for Next-Generation Biofuel Production

The growing demand for renewable energy has positioned microalgae, such as <i>Chlorella vulgaris</i>, as a promising feedstock for sustainable biofuel production. Leveraging nanotechnology, this study explores the multifaceted impacts of zinc oxide (ZnO) nanoparticles (NPs) on <i>C. vulgaris</i>, focusing on lipid biosynthesis, oxidative stress, biomass productivity, and photosynthetic pigment retention. The morphology of NPs and algae and their interactions were extensively studied using scanning electron microscopy (SEM), confocal microscopy, energy-dispersive X-ray spectroscopy (EDS), and X-ray photoelectron spectroscopy (XPS). The ZnO NP-enabled microalgae system enhanced lipid accumulation to as high as 48% at 50 mg/L. Biomass production and pigment content remained stable within the applied dose of NPs (20-50 mg/L), highlighting the resilience of <i>C. vulgaris</i> under NP exposure. However, at 100 mg/L, photosynthetic efficiency was disrupted, pigment content was reduced, and lipid yield declined to 30%. The enzymatic activity of catalase (CAT) revealed significant upregulation at higher ZnO NP concentrations, further corroborating the stress-induced metabolic shifts. This study also introduced a model for the Biofuel Suitability Score (BSS), which integrates lipid content, biomass productivity, oxidative stress levels, and pigment retention to identify the optimal conditions for biofuel production. The BSS peaked at moderate ZnO NP concentrations (30-50 mg/L), indicating a balance between lipid biosynthesis and cellular integrity. Beyond this threshold, oxidative damage compromises the biofuel potential, emphasizing the critical need for precise control of NP exposure. These findings highlight the potential of ZnO NPs to induce lipid accumulation through targeted stress modulation while maintaining biomass quality, advancing the application of nanotechnology in sustainable bioenergy systems. This study provides a scalable framework for integrating nanotechnology into renewable energy.