Novel mycosynthesis of cobalt oxide nanoparticles using Aspergillus brasiliensis ATCC 16404-optimization, characterization and antimicrobial activity.

AIMS: Investigate the capability of Aspergillus brasiliensis ATCC 16404 to mycosynthesize Co3 O4 -NPs. METHODS AND RESULTS: Mycelial cell-free filtrate of A. brasiliensis ATCC 16404 was applied for mycosynthesis of Co3 O4 -NPs. The preliminary indication for the formation of Co3 O4 -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 Co3 O4 -NPs and they were found to be: 72 h for reaction time, pH 11, 30°C, 100 rev min-1 for shaking speed in the darkness using 4 mmol l-1 of CoSO4. 7H2 O and 5·5% of A. brasiliensis dry weight mycelium (w/v). The mycosynthesized Co3 O4 -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 Co3 O4 -NPs and the microscopic ones confirmed the shape and size of the mycosynthesized Co3 O4 -NPs as quasi-spherical shaped, monodispersed nanoparticles with a nano size range of 20-27 nm. The mycosynthesized Co3 O4 -NPs have excellent magnetic properties and exhibited a good antimicrobial activity against some pathogenic micro-organisms. CONCLUSION: Ferromagnetic Co3 O4 -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.

Physiochemical properties of Trichoderma longibrachiatum DSMZ 16517-synthesized silver nanoparticles for the mitigation of halotolerant sulphate-reducing bacteria.

AIMS: In order to efficiently control the corrosive sulphate-reducing bacteria (SRB), the main precursor of the microbial influenced corrosion (MIC) in oil industry, the ability of Trichoderma longibrachiatumDSMZ 16517 to synthesize silver nanoparticles (AgNPs) was investigated and their biocidal activity against halotolerant SRB was tested. METHODS AND RESULTS: The mycelial cell-free filtrate (MCFF) bioreduced the silver ions (Ag+ ) to their metallic nanoparticle state (Ag0 ), which was presumptively indicated by the appearance of a dark brown suspension and confirmed by the characteristic absorbance of AgNPs at ʎ422nm . One-factor-at-a-time technique was used to optimize the effect of temperature, time, pH, fungal biomass and silver nitrate concentrations, stirring rates and dark effect. The dynamic light scattering (DLS) analysis revealed average AgNPs size and zeta potential values of 17·75 nm and -26·8 mV, respectively, indicating the stability of the prepared AgNPs. The X-ray diffraction (XRD) pattern assured the crystallinity of the mycosynthesized AgNPs, with an average size of 61 nm. The field emission scanning electron microscope (FESEM) and high-resolution transmission electron microscope (HRTEM) showed nonagglomerated spherical, triangular and cuboid AgNPs ranging from 5 to 11 ± 0·5 nm. The Fourier transform infrared spectroscopy (FT-IR) analysis of the mycosynthesized AgNPs affirmed the role of MCFF as a reducing and capping agent. A preliminary suggested mechanism for mycosynthesis of AgNPs was elucidated. The mycosynthesized AgNPs expressed high biocidal activity against a halotolerant planktonic mixed culture of SRB. The HRTEM analysis showed a clear evidence of an alteration in cell morphology, a disruption of SRB cell membranes, a lysis in cell wall and a cytoplasmic extraction after treatment with AgNPs. This confirmed the bactericidal effect of the mycosynthesized AgNPs. CONCLUSION: The biocidal activity of the mycosynthesized AgNPs against halotolerant planktonic SRB makes it an attractive option to control MIC in the petroleum industry. SIGNIFICANCE AND IMPACT OF THE STUDY: This research provides a helpful insight into the development of a new mycosynthesized biocidal agent against the corrosive sulphate-reducing bacteria.

Characterization and antimicrobial activity of silver nanoparticles mycosynthesized by Aspergillus brasiliensis.

AIMS: Since mycosynthesis of metal nanoparticles (NPs) is advertised as a promising and ecofriendly approach. Thus, this study aims to investigate the capability of Aspergillus brasiliensis ATCC 16404 for mycosynthesis of silver NPs (AgNPs). METHODS AND RESULTS: One-factor-at-a-time-technique was used to study the effect of different physicochemical parameters: the reaction time, pH, temperature, different stirring rates, illumination, and finally, the different concentrations of silver nitrate and fungal biomass on the mycosynthesis of AgNPs. The visual observation showed the characteristic brown colour formation due to the bioreduction of Ag+ ions to Ag0 by the mycelial cell-free filtrate (MCFF). The UV/visible spectrophotometric technique displayed a characteristic sharp peak at ʎ440 confirming the mycosynthesis of AgNPs. The zeta potential value -16·7 mV assured the long-term stability of AgNPs and the dynamic light scattering analysis revealed good dispersion and average particle size 77 nm. The energy dispersive X-ray spectroscopy displayed a maximum elemental distribution of silver elements. The X-ray diffraction spectroscopy demonstrated the crystallinity of the mycosynthesized AgNPs. The field emission scanning electron microscope and high-resolution transmission electron microscope revealed monodispersed spherical shaped AgNPs with average particle size of 6-21 nm. The FTIR analysis showed the major peaks of proteins providing the possible role of MCFF in the synthesis and stabilization of the AgNPs. The mycosynthesized AgNPs expressed good biocidal activity against different pathogenic micro-organisms causing some water-related diseases and health problems to local residents. CONCLUSIONS: This study proved that A. brasiliensis ATCC 16404 MCFF has good potential for mycosynthesis of AgNPs, which exhibited good antimicrobial effect on different pathogenic micro-organisms; thus, it can be applied for water disinfection. SIGNIFICANCE AND IMPACT OF THE STUDY: This research provides a helpful insight into the development of a new mycosynthesized antimicrobial agent.