Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic properties
Abstract Background Silver nanoparticles (AgNPs) have attracted considerable interest for their distinctive physicochemical properties and wide-ranging applications in nanomedicine, environmental catalysis, and antimicrobial applications. However, sustainable and robust biosynthesis methods remain a...
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2025-08-01
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| Series: | Microbial Cell Factories |
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| Online Access: | https://doi.org/10.1186/s12934-025-02815-9 |
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| author | Alessia Di Fraia Giovanni Dal Poggetto Michela Salamone Federica Carraturo Patrizia Contursi Marco Guida Danila Limauro Viviana Scognamiglio Manuela Rossi Gabriella Fiorentino |
| author_facet | Alessia Di Fraia Giovanni Dal Poggetto Michela Salamone Federica Carraturo Patrizia Contursi Marco Guida Danila Limauro Viviana Scognamiglio Manuela Rossi Gabriella Fiorentino |
| author_sort | Alessia Di Fraia |
| collection | DOAJ |
| description | Abstract Background Silver nanoparticles (AgNPs) have attracted considerable interest for their distinctive physicochemical properties and wide-ranging applications in nanomedicine, environmental catalysis, and antimicrobial applications. However, sustainable and robust biosynthesis methods remain a challenge. Results In this study, we report the biosynthesis of thermostable AgNPs using the secretome of Geobacillus stearothermophilus GF16, a thermophilic and metal-resistant bacterium isolated from the hydrothermal volcanic area of Pisciarelli, Italy. The synthesis was performed without specialized growth media, relying solely on the cell-free bacterial supernatant, and was systematically optimized by varying precursor concentration, temperature, pH, and reaction time. The nanoparticles were characterized by UV-Vis spectroscopy, dynamic light scattering, Fourier-transform infrared spectroscopy, scanning (SEM) and transmission (TEM) electron microscopy. Morphological analysis showed predominantly subspherical nanoparticles with average diameters of 17 ± 5 nm (SEM) and 16 ± 5–7 nm (TEM), depending on precursor concentration. Thermogravimetric analysis demonstrated excellent thermal stability with retention of structural integrity up to 120 °C, an exceptional feature among biogenic AgNPs. The obtained AgNPs exhibited remarkable radical scavenging activity, reaching up to 79% in DPPH and 75% in ABTS assays at 100 µg/mL, highlighting a level of antioxidant performance rarely observed in AgNPs of bacterial origin. In addition to their redox properties, the nanoparticles demonstrated efficient catalytic activity as evidenced by the complete degradation of Congo Red in 20 min and 4-nitrophenol in 35 min. Time-kill assays and minimum inhibitory concentration (MIC) also showed a broad-spectrum antimicrobial potential with complete inhibition of Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella Typhimurium at 100 µg/mL. Interestingly, MIC values were significantly lower than those reported for comparable AgNPs. Notably, the nanoparticles also displayed hemocompatibility, validated by hemolysis assays performed on both healthy and β-thalassemic erythrocytes, with hemolysis rates consistently below the 2% safety threshold. Conclusions Overall, this study presents the first comprehensive characterization of AgNPs biosynthesized by a thermophilic bacterium, highlighting their multifunctional potential. The use of a thermophilic bacterium as a robust and flexible microbial nanofactory offers a novel eco-friendly and scalable strategy for AgNP production. The resulting nanoparticles exhibit unique thermal stability, broad-spectrum bioactivity, and clinically relevant hemocompatibility, underscoring their promising applicability in nanomedicine, green catalysis, and environmental remediation. Graphical Abstract |
| format | Article |
| id | doaj-art-c438520f61bb45e896655bdc76a4cdfa |
| institution | Kabale University |
| issn | 1475-2859 |
| language | English |
| publishDate | 2025-08-01 |
| publisher | BMC |
| record_format | Article |
| series | Microbial Cell Factories |
| spelling | doaj-art-c438520f61bb45e896655bdc76a4cdfa2025-08-24T12:02:14ZengBMCMicrobial Cell Factories1475-28592025-08-0124112210.1186/s12934-025-02815-9Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic propertiesAlessia Di Fraia0Giovanni Dal Poggetto1Michela Salamone2Federica Carraturo3Patrizia Contursi4Marco Guida5Danila Limauro6Viviana Scognamiglio7Manuela Rossi8Gabriella Fiorentino9Department of Biology, University of Naples Federico IIInstitute of Polymers, Composites and Biomaterials, National Research CouncilDepartment of Biology, University of Naples Federico IIDepartment of Biology, University of Naples Federico IIDepartment of Biology, University of Naples Federico IIDepartment of Biology, University of Naples Federico IIDepartment of Biology, University of Naples Federico IIInstitute of Crystallography, Department of Chemical Sciences and Materials Technology, National Research CouncilDepartment of Earth Sciences, Environment and Resources, University of Naples Federico IIDepartment of Biology, University of Naples Federico IIAbstract Background Silver nanoparticles (AgNPs) have attracted considerable interest for their distinctive physicochemical properties and wide-ranging applications in nanomedicine, environmental catalysis, and antimicrobial applications. However, sustainable and robust biosynthesis methods remain a challenge. Results In this study, we report the biosynthesis of thermostable AgNPs using the secretome of Geobacillus stearothermophilus GF16, a thermophilic and metal-resistant bacterium isolated from the hydrothermal volcanic area of Pisciarelli, Italy. The synthesis was performed without specialized growth media, relying solely on the cell-free bacterial supernatant, and was systematically optimized by varying precursor concentration, temperature, pH, and reaction time. The nanoparticles were characterized by UV-Vis spectroscopy, dynamic light scattering, Fourier-transform infrared spectroscopy, scanning (SEM) and transmission (TEM) electron microscopy. Morphological analysis showed predominantly subspherical nanoparticles with average diameters of 17 ± 5 nm (SEM) and 16 ± 5–7 nm (TEM), depending on precursor concentration. Thermogravimetric analysis demonstrated excellent thermal stability with retention of structural integrity up to 120 °C, an exceptional feature among biogenic AgNPs. The obtained AgNPs exhibited remarkable radical scavenging activity, reaching up to 79% in DPPH and 75% in ABTS assays at 100 µg/mL, highlighting a level of antioxidant performance rarely observed in AgNPs of bacterial origin. In addition to their redox properties, the nanoparticles demonstrated efficient catalytic activity as evidenced by the complete degradation of Congo Red in 20 min and 4-nitrophenol in 35 min. Time-kill assays and minimum inhibitory concentration (MIC) also showed a broad-spectrum antimicrobial potential with complete inhibition of Staphylococcus aureus, Pseudomonas aeruginosa, and Salmonella Typhimurium at 100 µg/mL. Interestingly, MIC values were significantly lower than those reported for comparable AgNPs. Notably, the nanoparticles also displayed hemocompatibility, validated by hemolysis assays performed on both healthy and β-thalassemic erythrocytes, with hemolysis rates consistently below the 2% safety threshold. Conclusions Overall, this study presents the first comprehensive characterization of AgNPs biosynthesized by a thermophilic bacterium, highlighting their multifunctional potential. The use of a thermophilic bacterium as a robust and flexible microbial nanofactory offers a novel eco-friendly and scalable strategy for AgNP production. The resulting nanoparticles exhibit unique thermal stability, broad-spectrum bioactivity, and clinically relevant hemocompatibility, underscoring their promising applicability in nanomedicine, green catalysis, and environmental remediation. Graphical Abstracthttps://doi.org/10.1186/s12934-025-02815-9Silver nanoparticlesExtremophilesNanofactoryAntimicrobial activityCatalytic efficiencyBiocompatibility |
| spellingShingle | Alessia Di Fraia Giovanni Dal Poggetto Michela Salamone Federica Carraturo Patrizia Contursi Marco Guida Danila Limauro Viviana Scognamiglio Manuela Rossi Gabriella Fiorentino Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic properties Microbial Cell Factories Silver nanoparticles Extremophiles Nanofactory Antimicrobial activity Catalytic efficiency Biocompatibility |
| title | Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic properties |
| title_full | Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic properties |
| title_fullStr | Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic properties |
| title_full_unstemmed | Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic properties |
| title_short | Green synthesis of silver nanoparticles (AgNPs) from G. stearothermophilus GF16: stable and versatile nanomaterials with antioxidant, antimicrobial, and catalytic properties |
| title_sort | green synthesis of silver nanoparticles agnps from g stearothermophilus gf16 stable and versatile nanomaterials with antioxidant antimicrobial and catalytic properties |
| topic | Silver nanoparticles Extremophiles Nanofactory Antimicrobial activity Catalytic efficiency Biocompatibility |
| url | https://doi.org/10.1186/s12934-025-02815-9 |
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