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Introduction <p>Endophytic fungi of medicinal plants have gained recognition as probable sources of bioactive metabolites. In this study, sixteen endophytic fungi were isolated from basil (<i>Ocimum basilicum</i>) and screened for antibacterial activity using the agar well diffusion method. The most potent isolate was molecularly identified as <i>Aspergillus tamarii (A. tamarii)</i> by the ITS rDNA sequencing method, and the sequence was submitted to GenBank (accession no. PX474848.1). Then the strain was cultivated in different media to reduce production costs and enhance antibacterial metabolite production, including potato peel and <i>Portulaca oleracea</i> (<i>P. oleracea</i>) as low-cost alternatives to potato extract. The <i>P. oleracea</i>-based medium showed the highest antibacterial activity, with inhibition zones of 20.0&#xa0;mm against <i>Bacillus subtilis</i> (<i>B. subtilis</i>) and 23.0&#xa0;mm against <i>Staphylococcus aureus (S. aureus)</i>. For the green synthesis of zinc oxide nanoparticles (ZnO NPs), the fungal extract was mixed with an equal volume of 1.0&#xa0;mM zinc nitrate hexahydrate&#xa0;and exposed to gamma irradiation (20&#xa0;kGy). Characterization by UV–Vis. spectroscopy, DLS, XRD, SEM, and HRTEM confirmed the formation of ZnO NPs. The synthesized nanoparticles exhibited spherical and rod-shaped morphology and an average size of 70.34&#xa0;nm. Antibacterial activity was evaluated using the agar well diffusion assay and the broth microdilution method for MIC determination. The biosynthesized ZnO NPs showed inhibition zones of 26.0 ± 0.30&#xa0;mm against <i>B. subtilis</i> and 27.0 ± 0.13&#xa0;mm against <i>S. aureus</i>, with MIC values of 31.25&#xa0;µg/mL. Antibiofilm activity, assessed by the crystal violet tube method, showed inhibition rates of 50.32 and 55.33% against <i>B. subtilis</i> and <i>S. aureus</i>, respectively, while protein leakage analysis using the Bradford assay indicated increased membrane permeability in treated bacterial cells. Overall, the bioactive metabolites and the biosynthesized ZnO NPs showed promising antibacterial and antibiofilm activities, possibly linked to increased membrane permeability, suggesting their potential use in food and medical applications.</p> Aim <p>The objective of this study was to create a green synthesis of ZnO NPs using bioactive chemicals produced from endophytic fungi and gamma irradiation, as well as a cost-effective approach for producing bioactive metabolites from these fungi.</p> Impact statement <p>The current study presents a cost-effective and environmentally friendly process for producing bioactive metabolites from endophytic fungi and biosynthesizing ZnO NPs using gamma irradiation and endophytic fungal bioactive metabolites. The biosynthesized ZnO NPs present viable substitutes for traditional antibacterial agents, especially in food and medicinal applications that target gram-positive bacteria that are resistant to drugs.</p>

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Endophytic fungi-assisted biological synthesis of zinc oxide nanoparticles using gamma-rays for promising antibacterial and antibiofilm potential against some gram-positive bacteria

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  • 发表日期：

    2026年4月20日

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  • Sobhy S. Abdel-Fatah,
  • Nasser H. Mohammad,
  • Gharieb S. El-Sayyad

摘要

Introduction

Endophytic fungi of medicinal plants have gained recognition as probable sources of bioactive metabolites. In this study, sixteen endophytic fungi were isolated from basil (Ocimum basilicum) and screened for antibacterial activity using the agar well diffusion method. The most potent isolate was molecularly identified as Aspergillus tamarii (A. tamarii) by the ITS rDNA sequencing method, and the sequence was submitted to GenBank (accession no. PX474848.1). Then the strain was cultivated in different media to reduce production costs and enhance antibacterial metabolite production, including potato peel and Portulaca oleracea (P. oleracea) as low-cost alternatives to potato extract. The P. oleracea-based medium showed the highest antibacterial activity, with inhibition zones of 20.0 mm against Bacillus subtilis (B. subtilis) and 23.0 mm against Staphylococcus aureus (S. aureus). For the green synthesis of zinc oxide nanoparticles (ZnO NPs), the fungal extract was mixed with an equal volume of 1.0 mM zinc nitrate hexahydrate and exposed to gamma irradiation (20 kGy). Characterization by UV–Vis. spectroscopy, DLS, XRD, SEM, and HRTEM confirmed the formation of ZnO NPs. The synthesized nanoparticles exhibited spherical and rod-shaped morphology and an average size of 70.34 nm. Antibacterial activity was evaluated using the agar well diffusion assay and the broth microdilution method for MIC determination. The biosynthesized ZnO NPs showed inhibition zones of 26.0 ± 0.30 mm against B. subtilis and 27.0 ± 0.13 mm against S. aureus, with MIC values of 31.25 µg/mL. Antibiofilm activity, assessed by the crystal violet tube method, showed inhibition rates of 50.32 and 55.33% against B. subtilis and S. aureus, respectively, while protein leakage analysis using the Bradford assay indicated increased membrane permeability in treated bacterial cells. Overall, the bioactive metabolites and the biosynthesized ZnO NPs showed promising antibacterial and antibiofilm activities, possibly linked to increased membrane permeability, suggesting their potential use in food and medical applications.

Aim

The objective of this study was to create a green synthesis of ZnO NPs using bioactive chemicals produced from endophytic fungi and gamma irradiation, as well as a cost-effective approach for producing bioactive metabolites from these fungi.

Impact statement

The current study presents a cost-effective and environmentally friendly process for producing bioactive metabolites from endophytic fungi and biosynthesizing ZnO NPs using gamma irradiation and endophytic fungal bioactive metabolites. The biosynthesized ZnO NPs present viable substitutes for traditional antibacterial agents, especially in food and medicinal applications that target gram-positive bacteria that are resistant to drugs.