Omran B.A.Nassar H.N.Younis S.A.El-Salamony R.A.Fatthallah N.A.Hamdy A.El-Shatoury E.H.El-Gendy N.S.Department of Processes Design & DevelopmentEgyptian Petroleum Research InstituteNasr CityCairoEgypt; Department of MicrobiologyFaculty of PharmacyOctober University for Modern Sciences and Arts (MSA)6th of October CityEgypt; Depratment of Analysis and EvaluationEgyptian Petroleum Research InstituteNasr CityCairoEgypt; Department of Civil and Environmental EngineeringHanyang UniversitySeoulSouth Korea; Department of MicrobiologyFaculty of ScienceAin Shams UniversityAbbassiaCairoEgypt; Center of ExcellenceOctober University for Modern Sciences and Arts (MSA)6th of October CityEgypt2020-01-092020-01-09202013645072DOI : 10.1111/jam.14498PubMed ID : 31650655https://t.ly/R09pqScopusAims: Investigate the capability of Aspergillus brasiliensis ATCC 16404 to mycosynthesize Co3O4-NPs. Methods and Results: Mycelial cell-free filtrate of A. brasiliensis ATCC 16404 was applied for mycosynthesis of Co3O4-NPs. The preliminary indication for the formation of Co3O4-NPs was the change in colour from yellow to reddish-brown. One-factor-at a time-optimization technique was applied to determine the optimum physicochemical conditions required for the mycosynthesis of Co3O4-NPs and they were found to be: 72h for reaction time, pH 11, 30C, 100revmin?1 for shaking speed in the darkness using 4mmoll?1 of CoSO4.7H2O and 55% of A. brasiliensis dry weight mycelium (w/v). The mycosynthesized Co3O4-NPs were characterized using various techniques: spectroscopy including UV/Vis spectrophotometry, dynamic light scattering (DLS), zeta potential measurement, energy-dispersive X-ray analysis, Fourier transform infrared spectroscopy and X-ray diffraction; and vibrating sample magnetometry and microscopy including field emission scanning electron microscopy and high-resolution transmission electron microscopy. Spectroscopic techniques confirmed the formation of Co3O4-NPs and the microscopic ones confirmed the shape and size of the mycosynthesized Co3O4-NPs as quasi-spherical shaped, monodispersed nanoparticles with a nano size range of 20-27nm. The mycosynthesized Co3O4-NPs have excellent magnetic properties and exhibited a good antimicrobial activity against some pathogenic micro-organisms. Conclusion: Ferromagnetic Co3O4-NPs with considerable antimicrobial activity were for the first time mycosynthesized. Significance and Impact of the Study: The use of fungi as potential bionanofactories for mycosynthesis of nanoparticles is relatively a recent field of research with considerable prospects. 2019 The Society for Applied MicrobiologyEnglishantimicrobial activitycobalt oxide nanoparticlesmagnetic propertiesmycosynthesisphysicochemical factorsspectroscopic and microscopic techniquesAspergillus brasiliensisFungiArticlehttps://doi.org/10.1111/jam.14498.