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<p>Nanoparticles (NPs) synthesized via biological routes have gained significant attention due to their eco-friendly production and diverse biological applications. However, relatively few studies have explored the use of thermophilic bacteria for nanoparticle synthesis, despite their potential advantages in stability and enzyme robustness under extreme conditions. In particular, thermophilic microorganisms remain under explored for the extracellular biosynthesis of metal nanoparticles such as cerium (Ce) and zinc (Zn), and their comparative biological activities have not been sufficiently investigated. This study aimed to synthesize Ce and Zn nanoparticles using thermophilic bacterial strains and to evaluate their antimicrobial, antioxidant, DNA interaction, antibiofilm, microbial cytotoxic, and plant growth-promoting activities. Ce and Zn nanoparticles were synthesized extracellularly using <i>Anoxybacillus flavithermus</i> strain Gecek19 (T19-CeNPs and T19-ZnNPs) and <i>Geobacillus stearothermophilus</i> strain Gecek20 (T20-CeNPs and T20-ZnNPs). The biological activities of the nanoparticles were evaluated at different concentrations. Antioxidant activity was assessed using DPPH and metal chelating assays (12.5–200&#xa0;mg/L). DNA cleavage, microbial cell viability (125–500&#xa0;mg/L), biofilm inhibition (125–500&#xa0;mg/L), antimicrobial activity, and seed germination assays (12.5–500&#xa0;mg/L) were also performed. DPPH radical scavenging activities were 73.45%, 86.46%, 76.03%, and 82.60% for T19-CeNPs, T19-ZnNPs, T20-CeNPs, and T20-ZnNPs, respectively. Metal chelating activities were 67.12%, 64.56%, 72.40%, and 70.35%, respectively. The highest antimicrobial activity was observed for T19-ZnNPs with a Minimum Inhibitory Concentration (MIC) of 64&#xa0;mg/L against <i>Staphylococcus aureus</i> and <i>Enterococcus faecalis</i>. All nanoparticles exhibited single-stranded DNA cleavage activity and significantly reduced microbial cell viability. Biofilm inhibition reached up to 99.14% with T19-ZnNPs against <i>S. aureus</i>. Additionally, nanoparticle treatments showed positive effects on barley seed germination, particularly enhancing root and coleoptile development at appropriate concentrations. The study demonstrates that thermophilic bacteria are effective biofactories for Ce and Zn nanoparticle synthesis. The resulting nanoparticles exhibited strong multifunctional biological activities, including antioxidant, antimicrobial, antibiofilm, and plant growth-promoting effects, indicating their potential for biomedical and agricultural applications.</p>

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Extracellular synthesis of CeNPs and ZnNPs using thermophilic Anoxybacillus flavithermus and Geobacillus stearothermophilus bacteria, and their biological activities

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月9日

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  • Zelal Isik,
  • Sadin Özdemir,
  • Aysin Guzel Deger,
  • Serpil Kizildamar,
  • Erkan Yılmaz,
  • Mustafa Soylak,
  • Nadir Dizge

摘要

Nanoparticles (NPs) synthesized via biological routes have gained significant attention due to their eco-friendly production and diverse biological applications. However, relatively few studies have explored the use of thermophilic bacteria for nanoparticle synthesis, despite their potential advantages in stability and enzyme robustness under extreme conditions. In particular, thermophilic microorganisms remain under explored for the extracellular biosynthesis of metal nanoparticles such as cerium (Ce) and zinc (Zn), and their comparative biological activities have not been sufficiently investigated. This study aimed to synthesize Ce and Zn nanoparticles using thermophilic bacterial strains and to evaluate their antimicrobial, antioxidant, DNA interaction, antibiofilm, microbial cytotoxic, and plant growth-promoting activities. Ce and Zn nanoparticles were synthesized extracellularly using Anoxybacillus flavithermus strain Gecek19 (T19-CeNPs and T19-ZnNPs) and Geobacillus stearothermophilus strain Gecek20 (T20-CeNPs and T20-ZnNPs). The biological activities of the nanoparticles were evaluated at different concentrations. Antioxidant activity was assessed using DPPH and metal chelating assays (12.5–200 mg/L). DNA cleavage, microbial cell viability (125–500 mg/L), biofilm inhibition (125–500 mg/L), antimicrobial activity, and seed germination assays (12.5–500 mg/L) were also performed. DPPH radical scavenging activities were 73.45%, 86.46%, 76.03%, and 82.60% for T19-CeNPs, T19-ZnNPs, T20-CeNPs, and T20-ZnNPs, respectively. Metal chelating activities were 67.12%, 64.56%, 72.40%, and 70.35%, respectively. The highest antimicrobial activity was observed for T19-ZnNPs with a Minimum Inhibitory Concentration (MIC) of 64 mg/L against Staphylococcus aureus and Enterococcus faecalis. All nanoparticles exhibited single-stranded DNA cleavage activity and significantly reduced microbial cell viability. Biofilm inhibition reached up to 99.14% with T19-ZnNPs against S. aureus. Additionally, nanoparticle treatments showed positive effects on barley seed germination, particularly enhancing root and coleoptile development at appropriate concentrations. The study demonstrates that thermophilic bacteria are effective biofactories for Ce and Zn nanoparticle synthesis. The resulting nanoparticles exhibited strong multifunctional biological activities, including antioxidant, antimicrobial, antibiofilm, and plant growth-promoting effects, indicating their potential for biomedical and agricultural applications.