Aims Zinc oxide nanoparticles (ZnONPs) were successfully synthesized using the culture filtrate of the endophytic fungus Alternaria tenuissima a rapid, eco‐friendly and cost‐effective method. Methods and Results The rapid synthesis of ZnONPs was completed after 20 min as confirmed by UV–Vis spectroscopy. The synthesized ZnONPs showed a single‐phase crystalline structure. Dynamic light scattering analysis showed that the synthesized ZnONPs were monodispersed and the recorded polydispersity index value was 0·311. Zeta potential value of –23·92 mV indicated the high stability of ZnONPs. Transmission electron microscope revealed the spherical shape and the mean particle size was 46·58 nm. Functional groups present in the prepared samples of ZnONPs were confirmed by Fourier transform infrared spectroscopy. Additionally, the biological activities of in vitro antimicrobial, anticancer, antioxidant as well as the photocatalytic activities were evaluated. ZnONPs showed broad spectrum of antimicrobial potential against all the tested plant and human pathogens. Based on the MTT assay, ZnONPs inhibited the proliferation of normal human melanocytes, human breast and liver cancer cell lines with IC₅₀ concentrations of 55·76, 18·02 and 16·87 µg mL^‐1. ZnONPs exhibited promising antioxidant potential with 50% inhibitory concentration of 102·13 µg mL^‐1. Moreover, ZnONPs showed efficient degradation of methylene blue dye. Conclusions The synthesized ZnONPs showed promising activities that can be better explored in the near future for many medical, agricultural and industrial applications. Significance and Impact of the study This study suggests a new and alternate approach with the excellent biotechnological potentiality for the production of ZnONPs which could open up the way for the industrial manufacture of nanoparticles using microbial platforms.

In the light of the fast growing several applications of selenium nanoparticles (SeNPs) in different industrial and agricultural sectors, this paper was conducted to explore the suitability of endophytic fungi as nano-factories for SeNPs. Thus, 75 fungal isolates were recovered from plant tissues and tested for their efficacy to biosynthesize SeNPs. Four promising strains were found able to synthesis SeNPs with different characteristics and identified. These strains were Aspergillus quadrilineatus isolated from the twigs of Ricinus communis, Aspergillus ochraceus isolated from the leaves of Ricinus communis, Aspergillus terreus isolated from the twigs of Azadirachta indica, and Fusarium equiseti isolated from the twigs of Hibiscus rose-sinensis. The synthesized SeNPs were characterized by several techniques viz., UV–Vis, X-ray diffraction, Dynamic light scattering analyses, High resolution transmission electron microscopy, and Fourier transform infrared spectroscopy, to study their crystalline structure, particle sized distribution, and morphology. Furthermore, the in vitro antimicrobial and antioxidant activities were evaluated. SeNPs synthesized by the four strains showed potent antifungal and antibacterial potentials against different human and phyto- pathogens. Moreover, SeNPs synthesized by the respective strains showed promising antioxidant power with IC₅₀ values of 198.32, 151.23, 100.31, and 91.52 µg mL^− 1. To the best of our knowledge, this is the first study on the use of endophytic fungi for SeNPs’ biosynthesis. The presented research recommends the use of endophytic fungi as facile one-pot production bio-factories of SeNPs with promising characteristics.