Search Results (198)

A sequential two-stage chemo-biocatalytic process was investigated for the conversion of D-xylose to furfuryl alcohol (FOL), an important furan derivative widely used in the manufacture of resins, polymers, fuels, and other value-added products. In the first stage, D-xylose was dehydrated to furfural (FAL) in a ternary Betaine:Formic acid:Malonic acid–water (Bet:FA:MA–H₂O) reaction medium. Under the selected conditions, a FAL yield of 65.8% was obtained from 22.5 g/L D-xylose using 15 wt% Bet:FA:MA at 170 °C for 30 min. For the subsequent bioreduction stage, a recombinant Escherichia coli strain co-expressing the aldehyde reductase EutG and glucose dehydrogenase (GDH) was constructed. Using glucose as a co-substrate, EutG–GDH whole cells were able to reduce commercial FAL at concentrations up to 150 mM under the selected conditions of 40 °C and pH 7.5. For the sequential process using the D-xylose-derived dehydration liquor, the acidic reaction mixture was adjusted to pH 7.5 and diluted from 98.7 to 30.0 mM FAL before whole-cell bioreduction. The conditioned 30.0 mM FAL feed was essentially completely converted to FOL within 24 h. These results demonstrate the laboratory-scale feasibility of sequentially combining Bet:FA:MA–H₂O-mediated D-xylose dehydration with EutG–GDH whole-cell FAL reduction after interstage pH adjustment and dilution. Full article

Citrus postharvest blue mold caused by Penicillium italicum and green mold caused by P. digitatum are major diseases responsible for fruit decay and economic losses. Increasing fungicide resistance and concerns regarding the safety of chemical fungicides have created an urgent need for alternative control strategies. In this study, selenium microparticles (SeMPs) were biosynthesized by Lysinibacillus sphaericus N30 and characterized by scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy (SEM-EDS), X-ray diffraction (XRD), Raman spectroscopy, and dynamic light scattering (DLS). The control efficacy of N30-derived SeMPs against citrus postharvest diseases was evaluated using a 6-h post-inoculation treatment and a co-inoculation treatment, and their antifungal effects were further investigated by assessing reactive oxygen species (ROS) accumulation, membrane integrity, extracellular conductivity, and leakage of intracellular macromolecules. The N30-derived SeMPs were predominantly spherical and exhibited a Z-average hydrodynamic diameter of 656.5 nm with a PDI of 0.274. EDS identified Se as the predominant element, while XRD and Raman analyses supported the formation of predominantly amorphous elemental selenium. In vivo assays showed that 640 mg·L⁻¹ SeMPs completely prevented blue mold incidence in the P. italicum co-inoculation treatment, whereas 1280 mg·L⁻¹ completely suppressed blue mold under both application modes. Green mold caused by P. digitatum was completely suppressed at 1280–2560 mg·L⁻¹, with co-inoculation treatment generally showing greater efficacy than post-inoculation treatment. SeMP exposure was associated with increased intracellular ROS accumulation, loss of membrane integrity, increased extracellular conductivity, and leakage of intracellular macromolecules in both pathogens. P. italicum showed greater susceptibility to SeMPs-associated membrane perturbation than P. digitatum, consistent with its higher sensitivity in the fruit assays. These findings indicate that biogenic SeMPs produced by L. sphaericus N30 have potential as selenium-based antifungal materials for the management of citrus postharvest blue and green molds. Full article

Biological strategies for converting carbon dioxide (CO₂) into valuable compounds are attractive approaches for a carbon-neutral future. Bioelectrochemical systems (BESs) represent an innovative strategy for the control of microbial metabolism, in which electrochemical techniques are adopted to stimulate reductive and oxidative processes. Acetogenesis and methanogenesis are the two main chemoautotrophic pathways of CO₂ reduction usually present in anaerobic environments. Due to the syntrophic and competitive relationship between acetogens and methanogens, methanogenesis inhibition strategies should be adopted to direct CO₂ reduction towards acetate and fatty acids. In this work, an acetogen-enriched inoculum was produced by the bioaugmentation of Acetobacterium woodii in the heat-shocked and acid-treated inoculum. Then, by using H-cell reactors, without the use of any chemical inhibitor, this inoculum was tested in semi-continuous mode by imposing a dilution rate previously identified from growth kinetic assessment. Bioelectrochemical tests, conducted at −0.9 V and −0.7 V vs. SHE, showed the overcoming of acetogenesis on methanogenesis. At −0.7 V vs. SHE, acetate was produced at 0.0385 ± 0.009 mmol d⁻¹ and 0.0343 ± 0.010 mmol d⁻¹ in the absence and presence of bioaugmentation, respectively, with acetate cathodic coulombic efficiency (CCEs) of 68% and 64%. At −0.9 V vs. SHE, bioaugmentation markedly reduced methanogenesis, decreasing the methane production rate from 0.105 ± 0.012 to 0.007 ± 0.004 mmol d⁻¹, while acetate production reached 0.061 ± 0.025 mmol d⁻¹ with a CCE of 43%. Finally, the effect of bioaugmentation was demonstrated by cyclic voltammetry of the biocathode, which showed the increase in biocatalytic activity due to the presence of Acetobacterium woodii. Full article

Molecular docking was used to investigate the interactions between tirapazamine (a bioreductive anticancer drug) and bovine serum albumin (BSA), with emphasis on binding site localization and geometry. Docking simulations were performed using SwissDock with the AutoDock Vina 1.2.0 scoring engine. Warfarin (a canonical Sudlow Site I ligand) was docked under the same conditions as a reference to provide a relative comparison of binding orientation within Subdomain IIA. Docking results indicate that tirapazamine occupies a peripheral entrance-region position within Subdomain IIA, with limited polar interactions and substantial solvent exposure. In contrast, warfarin adopts a more enclosed binding orientation consistent with canonical Site I burial. UV–visible measurements across three independent titration experiments yielded apparent association constants of 2.30 ± 1.05 × 10⁴ M⁻¹ (mean ± SD), consistent with a weak interaction regime and supporting the docking results. Geometric analysis further shows that tirapazamine maintains greater minimum ligand–residue distances from core Site I residues than warfarin, consistent with reduced burial. This interpretation is further supported by the physicochemical profile of tirapazamine, which is characterized by low lipophilicity and high polarity, properties that are incompatible with deep binding in hydrophobic pockets (as seen with warfarin). Short-timescale molecular dynamics simulations (2 ns, triplicate) confirmed the stability of the docked poses, with tirapazamine exhibiting markedly lower ligand RMSD variability (0.247 ± 0.002 Å) than warfarin (0.578 ± 0.163 Å), consistent with a stable peripheral binding geometry. Together, these findings support a model in which tirapazamine associates weakly and peripherally with serum albumin, consistent with non-canonical Site I binding. Full article

Green synthesis of zinc oxide nanoparticles (ZnO NPs) represents a sustainable alternative to conventional chemical synthesis by employing biocatalytic systems under environmentally benign conditions. This study presents a systematic modeling approach based on Design of Experiments (DoEs) to optimize the green synthesis of ZnO nanoparticles intended for water treatment applications. Fractional factorial design was first applied to identify the most influential synthesis parameters, including precursor concentration, bio-reductant ratio, pH, temperature, and reaction time. Subsequently, response surface methodology using a D-optimal experimental design was employed to establish predictive mathematical models describing the relationships between process variables and nanoparticle size. The developed models enabled identification of optimal synthesis conditions and prediction of parameter combinations required to produce nanoparticles with targeted dimensions suitable for enhanced photocatalytic activity, antimicrobial performance, and colloidal stability. The proposed data-driven optimization strategy provides a robust, reproducible, and scalable protocol for green ZnO nanoparticle synthesis while minimizing reagent consumption and environmental impact. These findings contribute to the development of sustainable nanomaterials as the first step toward the future application of these ZnO nanoparticles as sustainable photocatalysts for water treatment. Full article

Selenite bioreduction by food-grade lactic acid bacteria enables mild production of selenium nanoparticles (SeNPs) together with selenium-enriched biomass. Here, a highly Se(IV)-tolerant isolate from Enshi soil was identified as Pediococcus acidilactici JD-21, which efficiently reduced 5 mmol/L Se(IV) and accumulated SeNPs with an average diameter of 46.4 ± 7.7 nm, potentially associated with protein- and polysaccharide-related biomolecules. Selenium enrichment markedly enhanced the antibacterial activity of JD-21 against Escherichia coli, Staphylococcus aureus and Salmonella enteritidis and improved survival in simulated gastric juice, indicating probiotic potential. In a mouse Streptococcus suis infection model, oral-gavage SeNPs alleviated infection-associated weight loss, restored antioxidant enzyme activities and reduced liver and spleen lesions. RNA-seq revealed 537 Se(IV)-responsive genes, with up-regulated redox, lipid/exopolysaccharide and transport pathways and down-regulated growth-related functions. These findings demonstrate that JD-21 is a promising food-grade chassis for producing biogenic SeNPs and selenium-enriched probiotics for selenium fortification and foodborne pathogen control. Full article

Acid mine drainage (AMD) is enriched with arsenite (As(III)), arsenate (As(V)), and jarosite. While jarosite can immobilize arsenic (As) through adsorption and other mechanisms, it dissolves and transforms into other minerals under near-neutral and reducing conditions via microbial mediation, thereby altering As fate. Fulvic acid (FA), a ubiquitous natural organic matter in the environment, has been proven to exhibit complex interactions with various iron minerals, Fe/S-metabolizing microorganisms, and As. However, the role of FA in the bioreduction and transformation of jarosite, as well as its subsequent impact on As mobility and fate, remains unclear. This study aims to elucidate the regulatory effect of FA on the biodissolution and transformation of jarosite, and the corresponding changes in As speciation. The results showed that FA exerted contrasting effects depending on arsenic speciation. In the As(III) treatments, FA intensified the inhibition of microbial dissimilatory sulfate reduction, suppressed sulfide production, and consequently limited orpiment formation. In contrast, in the As(V) treatments, FA enhanced the association of As(V) with jarosite surfaces, reduced aqueous As stress, and supported the persistence of As-tolerant sulfate-reducing populations. This promoted jarosite transformation toward mackinawite and facilitated As immobilization through orpiment precipitation. This study reveals the critical role of FA in the migration and transformation of As in mining areas, providing novel insights for optimizing AMD remediation strategies such as soil capping. Full article

The rising incidence of viral infections demands the creation of innovative, biocompatible antiviral drugs with broad-spectrum effectiveness. This study combines the green synthesis, optimization, and characterization of silver nanoparticles (AgNPs) utilizing Dacryodes edulis (D. edulis) extract, assessing their antiviral, and antimicrobial characteristics. AgNPs were synthesized through the bio-reduction of silver nitrate with D. edulis water extract as a reducing, capping and stabilizing agent. The synthesis was refined through a Design of Experiments methodology. The characterization techniques, UV-Vis, Fourier-transform infrared, transmission electron microscopy, and dynamic light scattering, validated the successful synthesis of AgNPs with an average size of 101.56 ± 28.22 nm (TEM) and 156 ± 0.81 nm (DLS), a polydispersity index of 0.34, and a zeta potential of −22 mV. High-resolution liquid chromatography–tandem mass spectrometry analysis identified some bioactive compounds which enhance the antimicrobial and antiviral properties of the samples. Enzyme kinetics experiments revealed substantial inhibitory efficacy against the SARS-CoV-2 papain-like protease (PL-pro), with AgNPs exhibiting a lower IC₅₀ (0.271 ± 0.051 mg/mL) than the D. edulis extract (0.337 ± 0.043 mg/mL). The AgNPs exhibited MIC of 0.063 mg/mL for E. coli, 0.125 mg/mL for S. aureus and 0.08 mg/mL for S. pyrogens. The corresponding MBC values were 0.125 mg/mL, 0.25 mg/mL and 0.31 mg/mL, respectively. The fungal strains C. glabrata and C. albicans displayed MIC of 0.63 mg/mL and 0.31 mg/mL, respectively, and MBC values of 0.63 mg/mL and 0.31 mg/mL, respectively. This study underscores the potential of D. edulis-derived AgNPs as a cost-efficient, environmentally sustainable, and highly bioactive antibacterial and antiviral nanomaterial, facilitating the advancement of nanotechnology-based therapies for viral infections. Full article

Arsenic (As) contamination in groundwater represents a critical global environmental health issue. The reductive dissolution of arsenic-bearing iron oxides by dissimilatory metal-reducing bacteria (DMRB) is a key biogeochemical process driving arsenic mobilization and release in groundwater. However, the mechanism of exogenous electron shuttles in this process remains poorly understood. This study investigated the impact of the quinone-based electron shuttle anthraquinone-2,6-disulfonate (AQDS) on the reductive dissolution of arsenic-loaded goethite by the model DMRB Shewanella putrefaciens CN32 (S.P CN32). The mobilization and transformation behaviors of arsenic and iron were compared under different pH conditions and using different arsenic-loading methods (coprecipitation vs. adsorption). Results demonstrated that AQDS acted as an electron transfer mediator. It significantly enhanced the reductive dissolution of Fe(III). It also significantly enhanced the reduction of As(V). These actions collectively accelerated arsenic release and mobilization. The study also revealed a competitive preferential order in microbial reduction, where the thermodynamically more favorable Fe(III) reduction preceded As(V) reduction. Environmental pH co-regulated this process. Its influence worked through microbial activity and mineral surface properties. A neutral pH was most conducive to the AQDS-mediated bioreduction of arsenic and iron. This study elucidates the critical role of electron shuttles in the biogeochemical cycling of arsenic in contaminated sites, providing a scientific basis for a deeper understanding of the formation mechanisms and risk assessment of high-arsenic groundwater. Full article

Green-synthesized metal nanoparticles are increasingly investigated for their antioxidative, antimicrobial, and stress-protective properties as eco-friendly and cost-effective alternatives to conventional chemical synthesis. Although agri-food wastes represent biomolecule-rich and sustainable resources, they remain less explored as biological matrices for green metal nanoparticle synthesis compared with plant and microbial extracts. The aim of this study was to optimize the synthesis and evaluate the bioactivity of silver nanoparticles derived from bergamot pomace, a polyphenol-rich agri-food waste. Synthesis parameters, including extract concentration, pH, extract-to-metal ratio, temperature, and reaction time, were optimized, and the nanoparticles were characterized by UV–Vis spectroscopy, dynamic light scattering, zeta potential analysis, and electron microscopy (TEM, STEM). ATR-FTIR and proteomic analyses were employed to investigate the molecular mechanisms involved in nanoparticle reduction, capping, and stabilization. The bergamot pomace-based silver nanoparticles exhibited a surface plasmon resonance peak at 430 nm, spherical morphology, good colloidal stability, and average diameters of 15–20 nm, without irreversible aggregation. A putative synthesis mechanism was proposed, involving Ag⁺ bioreduction mediated by polyphenols, ascorbic acid, and oxidoreductase-associated proteins, followed by stabilization through protein corona formation. Seed nanopriming assays on tomato and lettuce, together with in vitro antimicrobial tests against Pseudomonas syringae pv. tomato and Xanthomonas campestris pv. vesicatoria, demonstrated phytostimulatory and antimicrobial effects at very low nanoparticle concentrations. Overall, this study highlights bergamot pomace as a valuable resource for green silver nanoparticle synthesis, supporting its applicability in sustainable agriculture. Full article

This study investigates the preparation of a composite material by immobilizing Bacillus subtilis on biochar derived from chicken manure biogas residue for the removal of Cr(VI) from wastewater. The results demonstrated that the composite material (Bacillus subtilis immobilized biochar, BIB) achieved a maximum Cr(VI) removal efficiency of 94.1% in a 100 mg/L Cr(VI) solution within 4 h. The chicken manure-derived biochar not only served as an effective carrier for Bacillus subtilis but also enhanced the Cr(VI) removal efficiency through a synergistic effect with the microorganism. Functional groups such as phosphorus, carboxyl, and hydroxyl groups on the biochar surface played a key role in the sorption of Cr(VI). Bacillus subtilis primarily reduced Cr(VI) to Cr(III) by secreting cellular reductases. The combined action of biochar and Bacillus subtilis increased the Cr(VI) removal rate by 13.71% compared to biochar alone. This study presents a promising approach for Cr(VI) remediation in contaminated water and lays a theoretical foundation for the development of composite materials for Cr(VI) reduction. Full article

A significant driving force in nanotechnology development is the environmentally friendly synthesis of nanomaterials using natural extracts as reducing and stabilizing agents. In this study, silver and copper nanoparticles were synthesized and compared using two approaches: (1) a green synthesis pathway employing beetroot extract as a natural bio-reductant and stabilizer, and (2) a conventional chemical reduction method. The resulting nanoparticles were extensively characterized using transmission electron microscopy (TEM), X-ray diffraction (XRD), UV-Vis spectroscopy, and dynamic light scattering (DLS). The study revealed that the green synthesis route produced nanoparticles with well-defined morphology, high stability, and strong antimicrobial potential, outperforming those obtained via conventional chemical synthesis. Copper nanoparticles synthesized using beetroot extract exhibited particularly enhanced fungicidal and bactericidal properties, demonstrating the effectiveness of plant-based reducing agents in producing functional nanostructures. To further evaluate potential applications, the green-synthesized nanoparticles were incorporated into a polypropylene matrix, confirming their integrity and activity within the composite system. This work emphasizes the role of green synthesis in designing high-performance nanomaterials and highlights the promising capabilities of beetroot extract as a sustainable and efficient reducing and stabilizing medium for silver and copper nanoparticle production. Full article

Gastrodin is a bioactive component of traditional Chinese medicine, exhibiting anti-cancer, anti-inflammatory, antioxidant and neuroprotective properties. It has broad application prospects in health foods, pharmaceuticals and cosmetics. In recent years, the conversion of biomass-derived aldehydes into high-value-added chemicals has garnered widespread attention. In this study, gastrodin was biosynthesized via a dual-enzyme coupling system consisting of UGT_BL1-Δ60 and KpADH. Specifically, lignin-derived p-hydroxybenzaldehyde was used as the substrate. First, the glycosylation of p-hydroxybenzaldehyde by UGT_BL1-Δ60 yielded p-hydroxybenzaldehyde β-glucoside, generating the glycosylation reaction solution. Subsequently, bioreduction of the glycosylation product by KpADH produced gastrodin. Under the optimal reaction conditions (0.05 g/mL KpADH whole cells, 50 mM glucose, pH 7.5 and 30 °C) a gastrodin yield of 82.8% was achieved within 12 h. Moreover, both UGT_BL1-Δ60 and KpADH retained high catalytic activity after multiple reaction cycles. This study establishes a green and efficient biocatalytic approach for gastrodin synthesis, and also provides new insights into the high-value utilization of lignin. Full article

Coupling microbial catalysis with electrochemical stimulation offers a promising strategy for heavy metal remediation. This study investigates how potentiostatic control influences the bioreduction of hexavalent chromium (Cr(VI)) by Bacillus cereus strain DIF1 in a bioelectrochemical system. Cr(VI) reduction was evaluated under various applied cathodic potentials, and the highest reduction efficiency (91.45%) was achieved at +0.04 V after 24 h. This performance significantly surpassed that of the abiotic control (82.55%) and the open-circuit biotic control (9.25%), indicating that the applied potential enhances microbial Cr(VI) reduction beyond contributions from abiotic processes alone. Cyclic voltammetry (CV) revealed a distinct redox feature at +0.04 V with no corresponding reverse peak, indicating kinetically favored electron transfer during Cr(VI) reduction under this condition. Microscopic imaging confirmed that, under the applied potential, Bacillus cereus DIF1 formed filamentous connections, exhibited higher chromium accumulation on bacterial cells than on the surrounding carbon paper electrode, and developed a robust biofilm on the cathode surface. The system maintained consistent Cr(VI) reduction performance over three consecutive cycles, demonstrating good short-term operational reproducibility. These findings highlight the critical role of precise electrochemical control in modulating microbial Cr(VI) reduction and provide mechanistic insights into the interplay between electrode potential and bacterial activity. Full article

Background/Objectives: Flavonoids have been extensively investigated as reducing and stabilizing agents in the green synthesis of metallic nanoparticles. However, studies specifically employing pure naringin (NG) and naringenin (NGN) remain relatively scarce. Methods: In the present work, silver nanoparticles (AgNPs) were synthesized under controlled laboratory conditions using NG and NGN as bioreductants, and critical parameters governing nanoparticle formation were optimized. The synthesized AgNPs were comprehensively characterized using ultraviolet–visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), scanning transmission electron microscopy (STEM), energy-dispersive X-ray spectroscopy (EDX), and Fourier-transform infrared spectroscopy (FTIR). Results: The characterization analyses confirmed the successful formation of predominantly spherical AgNPs with average particle sizes of 17 nm (AgNG) and 20.4 nm (AgNGN). DLS analysis indicated zeta potentials of approximately −30 mV and PDIs of 0.45 (AgNG) and 0.29 (AgNGN), consistent with stable colloidal dispersions. Biological evaluations revealed that both AgNP systems exhibited notable antioxidant and antimicrobial activities. Furthermore, cytogenetic assessment using the Allium cepa assay demonstrated concentration-dependent alterations in mitotic index and chromosomal integrity, indicating biological activity at cellular level. Conclusions: Collectively, these results underscore the potential of flavonoid-mediated synthesis as an eco-friendly and effective approach for generating stable, bioactive nanomaterials with promising biological applications. Full article