Purification, Characterization, and Green Synthesis of ZnO Nanoparticles Using Purified Lignin Peroxidase from Fusarium odoratissimum for Environmental Remediation

Abstract The present study investigated agro-residue-induced production, purification, and application of ligninolytic peroxidase from Fusarium odoratissimum for enzyme-assisted zinc oxide nanoparticle (ZnO NP) synthesis. Among the tested lignin-rich agro-residues, wheat straw supported the highest enzyme production, reaching 0.18 µmol min − 1 on day 4. The enzyme was purified through sequential purification steps, resulting in an 18.55-fold increase in specific activity, with a final specific activity of 13.14 U mg − 1 and 17.73% recovery. The purified enzyme was subsequently employed as a defined protein preparation for ZnO NP synthesis. The synthesized ZnO NPs were characterized using UV–Vis spectroscopy, FTIR, FESEM, EDS, dynamic light scattering, zeta potential analysis, particle-size analysis, and XRD. The characterization results supported the formation of crystalline ZnO nanoparticles and the association of surface functional groups with the nanoparticles. EDS analysis showed Zn and O contents of 82.66 and 17.34 wt%, respectively. The ZnO NPs demonstrated concentration- and contact-time-dependent treatment efficiency toward Dikrong River water, achieving approximately 96.8% BOD and 55.0% COD removal at the highest tested dose. The nanoparticles also exhibited radical-scavenging activity in ABTS and DPPH assays, with greater apparent activity than the extracellular enzyme extract under the tested conditions. Overall, the findings highlight a waste-induced, defined purified-enzyme approach in which agro-residue-supported production and purification of the ligninolytic peroxidase constitute the experimental basis for downstream ZnO nanoparticle synthesis and environmental application.