Search Results (127)

Soil degradation resulting from intensive agricultural practices, the excessive use of agrochemicals, and climate-induced stresses has significantly impaired soil fertility, disrupted microbial diversity, and reduced crop productivity. Plant growth-promoting bacteria (PGPB) represent a sustainable biological approach to restoring degraded soils by modulating plant physiology and soil function through diverse molecular mechanisms. PGPB synthesizes indole-3-acetic acid (IAA) to stimulate root development and nutrient uptake and produce ACC deaminase, which lowers ethylene accumulation under stress, mitigating growth inhibition. They also enhance nutrient availability by releasing phosphate-solubilizing enzymes and siderophores that improve iron acquisition. In parallel, PGPB activates jasmonate and salicylate pathways, priming a systemic resistance to biotic and abiotic stress. Through quorum sensing, biofilm formation, and biosynthetic gene clusters encoding antibiotics, lipopeptides, and VOCs, PGPB strengthen rhizosphere colonization and suppress pathogens. These interactions contribute to microbial community recovery, an improved soil structure, and enhanced nutrient cycling. This review synthesizes current evidence on the molecular and physiological mechanisms by which PGPB enhance soil restoration in degraded agroecosystems, highlighting their role beyond biofertilization as key agents in ecological rehabilitation. It examines advances in nutrient mobilization, stress mitigation, and signaling pathways, based on the literature retrieved from major scientific databases, focusing on studies published in the last decade. Full article

Microbial Fuel Cell (MFC) is a novel bioelectrochemical system that catalyzes the oxidation of chemical energy in organic waste and converts it directly into electrical energy through the attachment and growth of electroactive microorganisms on the electrode surface. This technology realizes the synergistic effect of waste treatment and renewable energy production. A CF-NiO-PANI capacitor composite anode was prepared by loading polyaniline on a CF-NiO electrode to improve the capacitance of a CF electrode. The electrochemical characteristics of the composite anode were evaluated using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS), and the electrode materials were analyzed comprehensively by scanning electron microscopy (SEM), energy diffusion spectrometer (EDS), and Fourier transform infrared spectroscopy (FTIR). MFC system based on CF-NiO-PANI composite anode showed excellent energy conversion efficiency in potato starch wastewater treatment, and its maximum power density increased to 0.4 W/m³, which was 300% higher than that of the traditional CF anode. In the standard charge–discharge test (C1000/D1000), the charge storage capacity of the composite anode reached 2607.06 C/m², which was higher than that of the CF anode (348.77 C/m²). Microbial community analysis revealed that the CF-NiO-PANI anode surface formed a highly efficient electroactive biofilm dominated by electrogenic bacteria (accounting for 47.01%), confirming its excellent electron transfer ability. The development of this innovative capacitance-catalytic dual-function anode material provides a new technical path for the synergistic optimization of wastewater treatment and energy recovery in MFC systems. Full article

This study explores the feasibility of producing biohydrogen from winery wastewater using a dual-chamber microbial electrolysis cell (MEC). A mixed microbial consortium pre-adapted to heavy-metal environments and enriched with Geobacter sulfurreducens was anaerobically cultivated from diverse waste streams. Over 5000 h of development, the MEC system was progressively adapted to winery wastewater, enabling long-term electrochemical stability and high organic matter degradation. Upon winery wastewater addition (5% v/v), the system achieved a sustained hydrogen production rate of (0.7 ± 0.3) L H₂ L⁻¹ d⁻¹, with an average current density of (60 ± 4) A m⁻³, and COD removal efficiency exceeding 55%, highlighting the system’s resilience despite the presence of inhibitory compounds. Coulombic efficiency and cathodic hydrogen recovery reached (75 ± 4)% and (87 ± 5)%, respectively. Electrochemical impedance spectroscopy provided mechanistic insight into charge transfer and biofilm development, correlating resistive parameters with biological adaptation. These findings demonstrate the potential of MECs to simultaneously treat agro-industrial wastewaters and recover energy in the form of hydrogen, supporting circular resource management strategies. Full article

The contamination of natural waters with heavy metals is a global problem. Biosorption is an environmentally friendly and effective technology that offers advantages when metals are present in low concentrations. It also facilitates the recovery and conversion of metals, which are valuable resources. The removal capacity of Ag(I) and Zn(II) ions by Staphylococcus epidermidis CECT 4183 and the ability of its cell extract to synthesize Ag/AgCl and ZnO nanoparticles were investigated. Their biocidal capacity was evaluated. The factors involved were optimized and the mechanisms were studied. The optimal conditions for Ag(I) biosorption were pH 4.5 and a biomass dose of 0.8 g/L. For Zn(II), the biomass dose was 0.2 g/L and pH 4.2. A maximum biosorption capacity (Langmuir model) of 47.43 and 65.08 mg/g, respectively, was obtained. The cell extract promoted the synthesis of Ag/AgCl and ZnO nanoparticles with average sizes below 35 nm. The ZnO nanoparticles exhibited excellent inhibitory properties against planktonic cells of five microbial strains, with MIC values ranging from 62.5 to 250 µg/mL. Their response to biofilms remained between 70% and 100% inhibition at low concentrations (125 µg/mL). The studied bacteria show potential to remove heavy metals and promote the environmentally friendly synthesis of biocidal nanoparticles. Full article

Climate change will have a significant impact on saltwater intrusion in coastal aquifers between now and 2150. Global sea levels are predicted to rise somewhere between 0.5 and 1.8 m. To mitigate sea level rise, coastal aquifers will require intensive management to avoid inland migration of seawater that could impact water supplies. In addition to reducing pumping of freshwater, the construction and operation of salinity barriers will be required in many locations. Eleven types of salinity barriers were investigated, including physical barriers (curtain wall and grout curtains), infiltration canals filled with freshwater paralleling the coastline, injection of freshwater (treated surface water or wastewater), pumping or abstraction barriers, mixed injection and abstraction barriers, combined abstraction, desalination, and recharge (ADR), ADR hybrid barriers using various water sources including desalinated water and treated wastewater, compressed air barriers, aquifer storage and recovery dual use systems, biofilm barriers, and clay swelling or dispersion barriers. Feasibility of the use of each salinity barrier type was evaluated within the context of the most recent projections of sea level changes. Key factors used in the evaluation included local hydrogeology, land surface slope, water use, the rate of sea level rise, technical feasibility (operational track record), and economics. Full article

The majority of extant studies concentrate on the reactivation of dormant Anammox biomass or the recovery of activity under specific storage conditions. Research on rehabilitation strategies for anaerobic ammonium oxidation (Anammox) systems is limited, with the exception of research on inhibitory factors. The recovery characteristics of biofilm systems after collapse induced by varying degrees of ammonia-nitrogen and small-molecular organic compound composite shocks have not been thoroughly elucidated. This study addresses the collapse of Anammox biofilm systems caused by sodium acetate inhibition through multi-phase rehabilitation strategies, stoichiometric analysis, and microbial community succession dynamics. Two regression algorithms—Support Vector Regression (SVR) and eXtreme Gradient Boosting (XGBoost)—were employed to construct predictive models for Total Nitrogen Removal Efficiency (TNRE) and Total Nitrogen Removal Rate (TNRR) in the CANON system, with model performance evaluated via coefficient of determination (R²) and root mean square error (RMSE). Results demonstrated that after terminating moderate-to-high sodium acetate dosing (300 mg/L and 500 mg/L), reactors R300 and R500 achieved TNRE recovery to 57.98% and 58.86%, respectively, and TNRR of 0.281 and 0.275 kgN/m³·d within 60–100 days, indicating the reversibility of high-concentration sodium acetate inhibition but a positive correlation between recovery duration and inhibition intensity. Microbial community analysis revealed that Planctomycetota (including Candidatus_Kuenenia) rebounded to 46–49% relative abundance in R100, synchronized with TNRE improvement. In contrast, R300 and R500 exhibited ecological niche replacement of denitrifiers (Denitratisoma) and partial TNRE restoration despite enhanced performance. Model comparisons showed SVR outperformed XGBoost in TNRE prediction, whereas XGBoost demonstrated superior TNRR prediction accuracy with R² approaching 1 and RMSE nearing 0, significantly surpassing SVR. This work provides critical insights into recovery mechanisms under organic inhibition stress and establishes a robust predictive framework for optimizing nitrogen removal performance in CANON systems. Full article

Volatile organic compounds (VOC) are major contributors to the burgeoning air pollution issue, predominantly from industrial areas, with well-documented environmental and health risks, which demand efficient and sustainable control policies. This review analyzes the current technological challenges and investigates recent developments in biological treatment technologies for VOC-contaminated off-gases, including biofilters, biotrickling filters, and bioscrubber, as well as emerging technologies, such as bioaugmentation and microbial fuel cells (MFCs). Operational performance, economic feasibility, and adaptability to various industrial applications are assessed, alongside opportunities for integration with other technologies, including energy recovery technologies. Biological systems offer considerable advantages regarding cost savings and lower environmental impacts and enhanced operational flexibility, particularly when combined with innovative materials and microbial optimization techniques. Nevertheless, challenges persist, such as choosing the best treatment settings suited to different VOC streams and addressing biofilm control concerns and scalability. Overall, biological VOC treatments are encouraging sustainable solutions, though continued research into reactor design, microbial dynamics, and MFC-based energetic valorization is essential for broader industrial application. These insights cover advancements and highlight the continuous need for innovative prowess to forge sustainable VOC pollution control. Full article

Biofilm formation on orthopedic joint implants complicates diagnosis of periprosthetic joint infections (PJIs). Sonication of explanted orthopedic implants for diagnostic enhances pathogen detection, but it shows limitations in sensitivity and handling. We investigated whether the biosurfactant saponin could improve bacterial recovery from orthopaedic implants and thereby enhance infection diagnosis ex vivo. Orthopaedic material discs of 1 cm diameter were contaminated with different clinical bacterial PJI isolates. Biofilms of Staphylococcus epidermidis, Staphylococcus aureus, Escherichia coli, Cutibacterium avidum, and Cutibacterium acnes were grown on the discs, which were then treated with either saline solution or various concentrations of saponin. Next, the discs were vortexed or sonicated. Colony-forming units (CFUs) enumeration and time-to-positivity of liquid cultures were determined. Additionally, a novel 3D PJI soft tissue in vitro model was established to validate these findings in a more representative scenario. Median CFU enumeration showed that 0.001% (w/v) saponin as compared to saline solution increased CFUs recovery by 2.2 log₁₀ for S. epidermidis, 0.6 log₁₀ for S. aureus, 0.6 log₁₀ for C. avidum, 1.1 log₁₀ for C. acnes, and 0.01 log₁₀ for E. coli. Furthermore, saponin treatment resulted in a >1 log₁₀ increase in S. epidermidis CFU recovery from implants in the 3D tissue model compared to standard saline sonication. With that, we propose a novel two-component kit, consisting of a saponin solution and a specialized transportation box, for the efficient collection, transportation, and processing of potentially infected implants. Our data suggest that biosurfactants can enhance bacterial recovery from artificially contaminated orthopedic implants, potentially improving the diagnosis of PJIs. Full article

The objective of this study was an assessment of the anti-biofilm properties of fluoride non-thermal atmospheric plasma (FNTAP) generated using argon and hydrocarbon fluoride gas 1,1,1,2-tetrafluoroethane (TFE). These properties were evaluated by measuring the destruction and recovery of in vitro dual-species biofilms of Streptococcus mutans and Streptococcus sanguinis exposed to FNTAP at 5 or 10 standard cubic centimeters per minute (sccm) or argon non-thermal atmospheric plasma (ArNTAP) for 1 or 2 min, using resazurin-based reagent viability assays, colony forming units (CFU), culture media pH and live/dead staining. Both ArNTAP and FNTAP resulted in significant immediate reductions in bacterial load as compared to the control. Although ArNTAP did not significantly reduce biofilm regrowth, FNTAP treatment showed a bacterial load reduction of more than 5 log units of biofilm regrowth. FNTAP treatments significantly reduced the acidification of the culture medium after recovery incubation, indicating reduced living bacteria, with a pH of 6.92 ± 0.02 and 6.90 ± 0.03, respectively, for the 5 sccm and 10 sccm FNTAP treatments, as compared to a pH of 5.83 ± 0.26 for the ArNTAP treatment, and a significantly acidic pH of 4.76 ± 0.04 for the no-treatment groups. Our results suggest that FNTAP has exceptional anti-biofilm effects, and future directions of our research include the assessment of potential applications of FNTAP in clinical settings. Full article

An epilithic algal matrix (EAM) exhibits rapid expansion, recovery capacity, and high adaptability, leading to widespread distribution in degraded coral reef habitats. However, limited research on the dynamic processes of succession hinders a comprehensive understanding of EAM formation. To examine the influence of succession processes and environmental factors on the composition of EAM microbial communities, a three-factor (time × depth × attached substrate type) crossover experiment was conducted in the Luhuitou Reef Area, Sanya, China. Microbial community compositions were analyzed through 16S rRNA gene amplicon sequencing. The community was predominantly composed of proteobacteria (61.10–92.75%), cyanobacteria (2.47–23.54%), bacteroidetes (0.86–8.49%), and firmicutes (0.14–7.76%). Successional processes were found to significantly shape the EAM-associated microbial communities in the Luhuitou Reef Area. Proteobacteria played a crucial role in biofilm formation during this process, while cyanobacteria contributed to the structural complexity of microhabitats within the EAM. A chaotic aggregation stage of approximately one month was observed before transitioning into an expansion stage, eventually stabilizing into a low-diversity community. Although the relatively smooth substrate supported high biodiversity, microorganisms displayed no preference for the three different substrates. While no significant differences in community composition were observed at small-scale depths, cyanobacteria and bacteroidetes showed positive correlations with light and temperature, respectively. The EAM-associated microbial community exhibited higher complexity in the shallower regions under increased light intensity and temperature. Given the characteristics of the microbial community succession process, continuous monitoring of changes in microbial community structure and key taxa (such as proteobacteria and cyanobacteria) during EAM formation is recommended. Full article

This study aimed to examine the impacts of hydraulic retention time (HRT) and organic loading rate (OLR) on the alginate-like exopolymers’ (ALEs) recovery potential from a biofilm-based process. A lab-scale moving bed biofilm reactor (MBBR) was operated under different HRT (12.0, 6.0, and 2.0 h) and OLR (1.0, 2.0, and 6.0 kg COD/m³/d) conditions. The results demonstrated that the reduction in HRT and increase in OLR had remarkable effects on enhancing ALE production and improving its properties, which resulted in the ALE yield increasing from 177.8 to 221.5 mg/g VSS, with the protein content rising from 399.3 to 494.3 mg/g ALE and the enhanced alginate purity by 39.8%, corresponding to the TOC concentration increasing from 108.3 to 157.0 mg/g ALE. Meanwhile, to illustrate different ALE recovery potentials, microbial community compositions of the MBBR at various operational conditions were also assessed. The results showed that a higher relative abundance of EPS producers (29.86%) was observed in the MBBR with an HRT of 2.0 h than that of 12.0 h and 6.0 h, revealing its higher ALE recovery potential. This study yields crucial results in terms of resource recovery for wastewater reclamation by providing an effective approach to directionally cultivating ALEs. Full article

Microalgae microbial fuel cells (pMFCs) are distinguished by their ability to combine waste utilization with the simultaneous recovery of energy and valuable materials. The generation of high current density is linked to the efficient electron transfer to the anode via the anodic biofilm and the high photosynthetic activity of the microalgae cultivated in the cathode chamber. This review explores the impact of wastewater type on energy production and wastewater treatment. Additionally, it discusses the challenges related to microalgae growth in the cathode chamber, the necessity of aeration, and the sequestration of carbon dioxide from the anode chamber. The efficiency of microalgae in utilizing nutrients from various types of wastewater is also presented. In conclusion, the comparison between wastewater treatment and energy balance in pMFCs and conventional wastewater treatment plants is provided. On average, MFCs consume only 0.024 kW or 0.076 kWh/kg COD, which is approximately ten times less than the energy used by activated sludge bioprocesses. This demonstrates that MFCs offer highly efficient energy consumption compared to traditional wastewater treatment systems while simultaneously recovering energy through exoelectrogenic, bioelectrochemical processes. Full article

Optimal product synthesis in bioelectrochemical systems (BESs) requires a comprehensive understanding of the relationship between external voltage and microbial yield. While most studies assume constant growth yields or rely on empirical estimates, this study presents a novel thermodynamic model, linking anodic oxidation and cathodic carbon dioxide (${CO}_2$) reduction to methane (${CH}_4$) by growing microbial biofilm. Through integrating theoretical Gibbs free energy calculations, the model predicts electron and proton transfers for autotrophic methanogen and anode-respiring bacteria (ARB) growth, accounting for varying applied voltages and substrate concentrations. The findings identify an optimal applied cathodic potential of −0.3 V vs. the standard hydrogen electrode (SHE) for maximizing ${CH}_4$ production under standard conditions (pH 7, 25 °C, 1 atm) regardless of ohmic losses. The model bridges the stoichiometry of anodic and cathodic biofilms, addressing research gaps in simulating anodic and cathodic biofilm growth simultaneously. Additionally, sensitivity analyses reveal that lower substrate concentrations require more negative voltages than standard condition to stimulate microbial growth. The model was validated using experimental data, demonstrating reasonable predictions of biomass growth and ${CH}_4$ yield under different operating voltages in a multi substrate system. The results show that higher voltage inputs increase biomass yield while reducing ${CH}_4$ output due to non-optimal voltage. This validated model provides a tool for optimizing BES performance to enhance ${CH}_4$ recovery and biofilm stability. These insights contribute to finding optimum voltage for the highest ${CH}_4$ production for energy efficient ${CO}_2$ reduction for scaling up BES technology. Full article

The rapid development of the residential and industrial sectors produces a huge amount of treated domestic wastewater. The treated wastewater is discharged and could affect the environment in the long term. Improving the quality of treated domestic wastewater for water reclamation would benefit both sectors. This study aims to determine the efficiency of the biofilm-phytoremediation integration process in reclaiming domestic wastewater. A cuboid-shaped reactor was filled with 15 L of domestic wastewater, utilizing water hyacinth and a polyethylene carrier as supporting media for the process. The integrated reactor is tested in two phases: the initial adaptation of bacteria with domestic and synthetic wastewater (Phase I) and the integration process of biofilm-phytoremediation, based on the factors of NH₃-N concentration and hydraulic retention time (HRT), for 24 to 48 h (Phase II). In Phase II, pollutant removal was observed at varying NH₃-N concentrations: C1 (11–13 mg/L), C2 (9–11 mg/L), and C3 (3–5 mg/L). The study’s findings indicate a consistent performance in the first phase, with removal rates for COD and NH₃-N ranging between 86.7–100.0% and 79.0–99.6%, respectively. The reactor effectively removed pollutants at varying concentrations of NH₃-N, with average removal up to 100% (COD), 99% (NH₃-N), and 80% (PO₄³⁻). This integrated reactor shows the finest treated water quality outcomes for non-potable water recovery, as well as offers an alternative to resolve water scarcity for use in various sectors. Full article

Heavy metal pollution from industrial activities and poor waste disposal poses significant environmental and health threats to humans and animals. This calls for sustainable approaches to the cleanup of heavy metals. This review explores metal tolerance mechanisms of bacteria such as the formation of biofilms, efflux systems, and enzymatic detoxification. These mechanisms allow bacteria communities to adapt and survive in contaminated environments. These adaptations are enhanced by mutations in the bacteria genes and by horizontal gene transfers, enabling bacteria species to survive under environmental stress while simultaneously contributing to nutrient cycling and the decomposition of organic matter. This review further explores the symbiotic interactions between bacteria, plants, and animals. These relationships enhance the metal tolerance ability of the different living organisms involved and are also very important in the bioremediation and phytoremediation of heavy metals. Plant growth-promoting rhizobacteria, Rhizobium, and Bacillus species are very important contributors to phytoremediation; they improve heavy metal uptake, improve the growth of roots, and plants resilience to stress. Moreover, this review highlights the importance of genetically engineered bacteria in closed-loop systems for optimized metal recovery. This offers environmentally friendly and sustainable options to the traditional remediation methods. Engineered Cupriavidus metallidurans CH34 and Pseudomonas putida strain 15420352 overexpressing metallothioneins have shown enhanced metal-binding capabilities, which makes them very effective in the treatment of industrial wastewaters and in biosorption applications. The use of engineered bacteria for the cleanup of heavy metals in closed-loop systems promotes the idea of a circular economy by recycling metals, thus reducing environmental waste. Multidisciplinary research that integrates synthetic biology, microbial ecology, and environmental science is very important for the advancement of metal bioremediation technologies. This review’s analysis on bacterial metal tolerance, symbiosis, and bioengineering strategies offers a pathway to effective bioremediation options, for the reclamation of heavy metal-polluted environments while promoting sustainable environmental practices. Full article