Search Results (131)

In bioleaching processes, the use of microbial consortia establishes a favourable environment that supports the growth and activity of multiple microorganisms, thereby enhancing their synergistic interactions during leaching. Mineral dissolution efficiency is consistently higher in consortia than in monocultures. Acidithiobacillus thiooxidans and Acidithiobacillus ferrooxidans exhibit metabolic complementarity and synchrony, including interactions with thermophilic microorganisms. Bioleaching is typically conducted under highly acidic conditions (pH 1–2), where microorganisms utilize essential resources such as nutrients and oxygen, while tolerating elevated concentrations of heavy metals. This review aims to examine the characteristics and current applications of microbial consortia, with particular emphasis on their interactions with heavy metals, the behaviour of their exopolysaccharides (EPS) under toxic conditions, their role in bioremediation across diverse environmental systems, and their potential for industrial implementation. Microbial consortia represent a high-value biotechnological tool in both mining and environmental remediation. Their synergistic interactions enable enhanced efficiency in the bioleaching of sulphide minerals, promoting the mobilization of both economically valuable and contaminant metals, and significantly outperforming individual cultures. Consequently, microbial consortia constitute a versatile, resilient, and eco-efficient platform for metal recovery and the mitigation of environmental liabilities. This review focuses on the applications of bacterial consortia in bioleaching processes and highlights their potential for emerging and future use. Full article

Micro- and nanoplastics (MNPs) are increasingly contaminating atmospheric particulates, yet their influence on PM_2.5 chemistry and toxicity remains poorly understood. This study investigates how secondary MNPs derived from common products (water bottles, coffee cups, and food plates) alter the properties of PM_2.5. We evaluated PM_2.5 leaching characteristics, oxidative potential, inflammatory activity, and bacterial-based cytological and metabolomic responses after 24 h of exposure to three MNP doses. MNPs markedly altered PM_2.5 chromophoric composition, with bottle-derived (PET) MNPs inducing the strongest increases in aromaticity, humification, and slope factor, followed by coffee cups (PLA/paper) and food plates (PP). These leaching shifts aligned with polymer-specific redox behaviors: bottle-derived MNPs enhanced antioxidant enrichment at high PM_2.5, whereas cup-derived MNPs produced the most pronounced protein-denaturation-based inflammatory activity. Escherichia coli assays showed non-linear growth responses, elevated reactive oxygen species, altered carbohydrate secretion, and membrane and protein perturbations that paralleled PM_2.5 chemical reactivity. FTIR metabolomic fingerprints revealed dose- and polymer-dependent disruptions in polysaccharide, lipid, and protein domains. Overall, the results demonstrate a mechanistic cascade in which MNP exposure reshapes PM_2.5 chemistry, amplifies oxidative and inflammatory potential, and culminates in measurable cytological and metabolic stress, with polymer identity (PET > PLA/paper > PP) as the dominant driver. Full article

This study investigates the mechanical properties, moisture stability, and environmental safety of microbial-induced carbonate precipitation (MICP)-treated phosphogypsum (PG)-based mixtures (MPGT) for road base utilization. Optimal cementation solution concentrations and bacterial-to-cementation solution ratios were determined via unconfined compressive strength (UCS), California bearing ratio (CBR), and splitting tensile strength tests. Durability was compared with untreated mixtures, and enhancement mechanisms were analyzed using XRD, SEM, and FTIR. Additionally, toxicity leaching tests evaluated environmental safety. Results indicated optimal parameters of 2.0 mol/L cementation solution and a 2:1 bacterial/cementation solution ratio for maximum mechanical strength. Under these conditions, MPGT durability significantly improved compared to untreated mixtures. Mechanism analysis revealed that MICP-generated calcium carbonate coats PG particles and fills voids, enhancing strength and durability. Furthermore, F⁻ and PO₄³⁻ leaching concentrations were significantly reduced. In summary, MICP improves the mechanical performance, durability, and environmental safety of PG-based mixtures, promoting PG recycling in road engineering. Full article

Jurassic–Cretaceous marine–continental carbonate–evaporitic sequences in the Neuquén Basin of Argentina host numerous stratabound Ba–Sr deposits. Mineralization (Sr–barite, Ba–celestine, and minor Pb–Zn–Cu–Fe sulphides) occurs as bedding parallel lenses and crosscutting veins. The stratiform mineralization is formed by replacements of carbonate and gypsum beds and often exhibits typical zebra textures. Dissolution processes associated with Neogene regional uplift produced karstic cavities where a new generation of barite was deposited. Regionally, W to E distribution of carbonates/evaporites and that of Ba–Sr deposits is coincidental. Lower Cretaceous Sr–Ba deposits are spatially related to large N-S reverse faulting, frequently limited to the eastern limb of the folded structures. Average δ¹⁸O and δ³⁴S of stratiform and crosscutting vetiform mineralization do not differ significantly, suggesting a common source of sulphate and cations. Deposits spatially linked to areas with magmatic activity and those that are not have similar isotopic values, compatible with bacterial and/or thermochemical reduction of contemporaneous seawater sulphate, although sulphides only occur in deposits with evidence of nearby magmatic activity. Thermal convection of basinal brines leached metals from the Mesozoic sedimentary pile; Ba and Sr were extracted from siliciclastic and carbonate rocks, and sulphur from evaporite layers. Fluids related to Tertiary magmatism helped producing an epithermal mineral association composed of barite, quartz, adularia, and minor sulphides/sulphosalts hosted by veins. Arroyo Nuevo mine (Ba) is different, as it seems to be the product of hydrothermal SedEx deposition onto the anoxic seafloor. Full article

Mafic mine tailings are highly resistant to bioleaching due to their silicate-rich composition, low sulfide content, and strong buffering capacity. This study aimed to assess the potential use of heterotrophic bioleaching to promote the release of metals from mafic tailings by evaluating the organic acid production and leaching capabilities of indigenous bacterial isolates and a known lactic acid producer, Lactiplantibacillus plantarum ATCC 8014. Indigenous acid-producing heterotrophic bacteria were isolated from a vanadium-titanium-bearing magnetite tailings in Québec, Canada, and screened for organic acid production in various culture media. The most active bacteria were L. plantarum and two isolates identified by their 16S rRNA gene as Enterococcus (CBGM-1C) and Acetobacter (BL-F) sp. They produced significant quantities of lactic acids, followed by acetic, citric, and gluconic acids during glucose metabolism, through fermentative or oxidative pathways. A two-step bioleaching process was implemented, consisting of an initial organic acid production phase followed by tailings leaching at 5% pulp density over 10 days at 30 °C. Metal solubilization and mineralogical analyses demonstrated strain-dependent and metal-specific mobilization, with zinc being the only element efficiently leached (up to ~74% recovery by L. plantarum). XRD analyses confirmed partial dissolution and reduced crystallinity of key silicate phases without secondary mineral formation. These findings indicate that heterotrophic leaching can selectively mobilize more labile metals such as Zn from alkaline, silicate-rich tailings, although its overall efficiency for refractory elements remains limited under the tested conditions. Full article

To facilitate the large-scale recycling of phosphogypsum (PG) as a construction material and mitigate the environmental safety concerns associated with its stockpiling or discharge, this study proposes an innovative approach. The method employs modified (acid-treated) basalt fibers (MBF) synergistically combined with microbially induced carbonate precipitation (MICP) technology for PG solidification. This synergistic MBF–MICP treatment not only enhances the strength and further improves the toughness of the solidified PG but also effectively immobilizes heavy metals within the PG matrix. Bacterial attachment tests conducted on fibers subjected to various pretreatment conditions revealed that the maximum bacterial adhesion occurred on fibers treated with a 1 mol/L acid concentration for 2 h at 40 °C. However, MICP mineralization experiments performed on these pretreated fibers determined the optimal pretreatment conditions for mineralization efficiency to be an acid concentration of 0.93 mol/L, a treatment duration of 0.96 h, and a temperature of 30 °C. Unconfined compressive strength (UCS) tests and calcium carbonate content measurements identified the optimal reinforcement parameters for MBF–MICP-solidified PG as a fiber length of 9 mm and a fiber dosage of 0.4%. Furthermore, comparative analysis demonstrated that the UCS and toughness of MBF–MICP-solidified PG were superior to those of bio-cemented PG specimens treated with unmodified fibers or without any fiber reinforcement. It was found by scanning electron microscopy that there was an obvious phosphogypsum particle-fiber-calcium carbonate precipitation interface in the sample, and the fiber had a bridging effect. Finally, heavy metal leaching tests conducted on the solidified PG confirmed that the leached heavy metal concentrations were below the detection limit, complying with national discharge standards. Full article

Excessive nitrogen fertilization can degrade soil quality by inducing nutrient leaching, disrupting the microbial balance, and impairing plant reproductive growth, ultimately reducing crop yields. Optimizing nitrogen application rates and integrating humic acid fertilizers are promising strategies for enhancing soil fertility and improving agricultural productivity. The experimental design included four nitrogen application rates (N0:0 kg ha⁻¹, N1:120 kg ha⁻¹, N2:150 kg ha⁻¹, and N3:180 kg ha⁻¹) with and without humic acid (H: 1500 kg ha⁻¹). Key findings revealed that: (1) The combined application of humic acid (1500 kg ha⁻¹) and medium nitrogen (150 kg ha⁻¹) significantly increased the contents of soil organic carbon (SOC), total nitrogen (TN), available phosphorus (AP), and available potassium (AK) by an average of 21.7% (p < 0.05), 90.5% (p < 0.01), 59.4% (p < 0.05), and 11.3% (p < 0.05), respectively (two-year mean), with significant interactive effects between nitrogen and humic acid on nutrient accumulation; (2) humic acid supplementation significantly increased soil bacterial abundance and diversity: under the combined treatment of medium nitrogen (150 kg ha⁻¹) and humic acid, the bacterial Ace index (indicating species richness) and Shannon index (indicating community diversity) increased by an average of 0.76% and 0.30%, respectively, compared with the single medium nitrogen treatment (p < 0.05), promoting a more balanced microbial community; and (3) quinoa yields improved by 24.62–66.83% with humic acid application, with the highest yield increase observed under the moderate nitrogen rate (150 kg ha⁻¹) in combination with humic acid. These results demonstrate that integrating humic acid with optimized nitrogen fertilization (150 kg ha⁻¹ N + 1500 kg ha⁻¹ HA) can effectively improve soil nutrients and enhance quinoa productivity. The increases in soil total nitrogen (TN, p < 0.01), available phosphorus (AP, p < 0.05), bacterial Shannon index (p < 0.05), and quinoa yield (p < 0.01) under this combined treatment were all significantly higher than those under single nitrogen fertilization or humic acid application, confirming the synergistic effect of the two fertilizers. Full article

Exposure to PM2.5 and its associated micropollutants, including micro- and nanoplastics, has been strongly linked to adverse health effects in humans. The risk posed by micro/nanoplastics can be attributed to the particles themselves and their ability to leach into the surrounding environment. However, the impact of micro/nanoplastics on the surrounding environment through leaching is still underestimated. In this study, we conducted ex situ experiments involving micro/nanoplastics and PM2.5 at various particulate matter mass concentrations and exposure times (1–336 h). The micro/nanoplastics were then removed from the PM2.5 media, and the aromaticity, light absorption, zeta potential, and oxidative potential of the PM2.5 were measured. Furthermore, the toxicity of the PM2.5 was investigated using a bacterial model by Staphylococcus aureus. Changes in the aromaticity, light absorption, zeta potential, and oxidative potential of PM2.5 indicated the impact of the micro/nanoplastics on the PM2.5. For example, PM2.5 exhibited higher aromaticity in the initial exposure stages (2–4% and 9–11%), whereas its light absorption (0.5–6-fold) increased with prolonged exposure to micro/nanoplastics. Overall, more negative zeta potentials and higher oxidative inputs (~6–40%) were obtained in PM2.5 after micro/nanoplastic treatment. The bacterial model revealed that the viability and biofilm formation of bacteria were affected by PM2.5 exposed to micro/nanoplastics, compared to PM2.5 not exposed to micro/nanoplastics, for example, 0.5–2-fold higher bacterial activity with longer MNP exposure and 4–39% higher biofilm formation. Furthermore, the oxidative stress-related bacterial indicators were primarily influenced by the aromaticity, zeta potential, and oxidative potential of PM2.5. The results of this study suggest that the bacterium Staphylococcus aureus can adapt to PM2.5 contaminated with micro/nanoplastics. Therefore, this study highlights the potential impact of micro/nanoplastics on bacterial adaptation to environmental contaminants and antibiotic resistance via PM2.5. Full article

Nutrient cycling has barely been studied in acidic environments and may have an important influence on the evolution of the microbial communities. In this research, we studied nutrient sources and fluxes in acidic metal-mine pit lakes to evaluate their relationship with the lakes’ microbial ecology. Nutrient concentrations (including phosphorus, nitrogen, and dissolved inorganic carbon) increase with depth in all the studied pit lakes. Phosphorus comes mainly from the leaching of the host rock and is rapidly scavenged from the aqueous phase in the oxygenic and Fe(III)-rich mixolimnion due to adsorption on ferric precipitates (schwertmannite, jarosite), which leads to an important P-limitation in the photic zone. Below the chemocline, however, the sum of phosphorus inputs (e.g., settling of algal biomass, desorption from the ferric compounds, microbial reduction of Fe(III)-sediments) sharply increases the concentration of this element in the anoxic monimolimnion. Nitrogen is very scarce in the host rocks, and only a limited input occurs via atmospheric deposition followed by N-uptake by algae, N-fixation by acidophilic microorganisms, sedimentation, and organic matter degradation in the sediments. The latter process releases ammonium to the anoxic monimolimnion and allows some nitrogen cycling in the chemocline. Soluble SiO₂ in the mixolimnion is abundant and does not represent a limiting nutrient for diatom growth. Differences in phytoplankton biomass and extent of bacterial sulfate reduction between relatively unproductive lakes (San Telmo) and the more fertile lakes (Cueva de la Mora) are likely caused by a P-limitation in the former due to the abundance of ferric iron colloids in the water column. Our results suggest that phosphorus amendment in the photic zone could be an efficient method to indirectly increase acidity-consuming and metal-sequestering bacterial metabolisms in these lakes. Full article

De-sealing, or depaving, is increasingly adopted to restore soil permeability and support green infrastructure, yet its potential to recover soil functions remains insufficiently understood. This study reports one year of soil monitoring following the de-sealing of a brownfield site in Milan (Italy). It compares the evolution of pedoclimatic parameters in sealed and de-sealed soils and assesses the suitability of recycled aggregates (RAs) from demolition waste as a soil-forming material. Buried sensors continuously recorded pedoclimatic parameters, temperature, water content, and oxygen concentration, while periodic sampling was carried out to analyse soil chemical properties, bacterial community composition, and the quality of percolation water (heavy metal content). De-sealing immediately improved pedoclimatic conditions, enhancing soil aeration, water regulation, and heat exchange capacity. No significant variation was detected in soil chemical properties, apart from pH fluctuations linked to the leaching of alkaline ions from concrete-based RAs. The presence of RAs caused no adverse effects on either soil or percolation water. Bacterial community composition was strongly associated with soil organic carbon, C:N ratio, and soil water content, without showing clear temporal trends. Overall, the study demonstrates that de-sealing rapidly triggers soil functional recovery and that, when properly characterised for composition and contamination risk, RAs pose no evident threat to the surrounding environment. Full article

Biochar is increasingly recognized as a multifunctional soil amendment that improves soil fertility, nutrient cycling, and crop productivity. Studies across field, greenhouse, and incubation settings show that biochar enhances nutrient retention, reduces leaching, and regulates carbon, nitrogen, and phosphorus cycling. Its effects are shaped by intrinsic physicochemical properties and interactions with soil minerals, microbial communities, and enzymatic processes. Short-term benefits of biochar applications often include improved nutrient adsorption and water regulation, while long-term applications support stable soil organic matter formation, root development, and fertilizer use efficiency. Biochar also reshapes soil microbial diversity and activity. Beneficial bacterial groups such as Proteobacteria and Actinobacteria, along with fungi such as Mortierella, respond positively, enhancing nitrogen fixation, phosphorus solubilization, and organic matter decomposition. Meanwhile, biochar applications could suppress pathogens. Enzyme activities, including urease and phosphatase, are typically stimulated, driving nutrient mobilization. Yet outcomes remain context-dependent, with biochar feedstock, application rate, soil conditions, and crop type influencing results; excessive use may suppress enzymatic activity, reduce nutrient availability, or shift microbial communities unfavorably. Practically, biochar can improve fertilizer efficiency, restore degraded soils, and reduce greenhouse gas emissions, contributing to climate-smart agriculture. Future work should prioritize long-term, multi-site trials and advanced analytical tools to refine sustainable application strategies. Full article

The cardinal Physiology of Gut Health in monogastric animals such as swine and poultry is vital. It is critical for digestive efficiency, immune status, and production levels. This system is related not only to the digestion and absorption of nutrients from feed ingredients contributing to growth and feed utilization efficiency but also to having a strategic microbiota that supports immunity and pathogen resistance, as well as metabolic support. Gut disease, for example, bacterial, viral, or parasitic infection, diet, or stress, can reduce nutrient digestion and absorption. They can also suppress the immune system and render patients more prone to disease. These are efficiency degradations and increase veterinary and husbandry costs. In addition, nutrient absorption because of deteriorated gut health can affect the environment in different ways: removal of nutrients through leaching and the release of gases (including CH₄ and NH₄). These pressures have led to a focus on the gut in animal research to improve the welfare of animals and ensure sustainable practices in animal production. Recent studies have included the use of probiotics, prebiotics, and other feed additives to enhance the positive effects of the gut microbiota. These are also intervention points to increase nutrient absorption and animal well-being, in turn sustainability. Such approaches are expected to promote a stable microbial community with less dependence on the use of antibiotics, less waste generation, and less environmental impact from animal farming. This review provides a critical evaluation of the current literature on gut health in monogastric livestock, with pigs and poultry as the principal focus. We also considered the impact of gut health on production efficiency and Environmental sustainability. Current progress in nutritional modulation of gut health for increased productivity, enhanced animal welfare, and better profitability are presented. Gut-related biological mechanisms are linked to practical nutritional strategies, and subsequently to animal welfare, production efficiency, and environmental effects, offering a coherent concept for moving from mechanism to system-level sustainability. Full article

The efficiency of the sorption–biological method for treatment of oil-polluted coastal substrates (soil and sand) of the Barents Sea under low temperature (10 °C) using the active hydrocarbon-oxidizing bacterial strain Rhodococcus erythropolis HO-KS22 was assessed in the laboratory. The highest rate of hydrocarbon degradation was in sand polluted with a low-density oil emulsion and in soil polluted with a medium-density oil emulsion. Sorption–biological treatment increased the rate of hydrocarbon degradation in sand by 3–4 times during the first month and enhanced the overall efficiency by 20% over a three-month period. The use of sorbents (granular activated carbon, thermally activated vermiculite and peat) both in sand and soil prevents secondary pollution of coastal ecosystems, since it significantly reduces the hydrocarbons’ desorption and their leaching by water. Rhodococcus erythropolis HO-KS22, in combination with sorbents, can be applied during the biological remediation of coastal sandy substrates following the initial removal of emergency oil spills. However, for biological treatment of oil-polluted soils of the Barents Sea coast, further selection of active strains of hydrocarbon-oxidizing bacteria resistant to low pH values and temperatures typical for this region is necessary. The use of microbiological preparations without taking into account the soil and climatic factors of the region may be ineffective, which will increase the cost of remediation of the territory without significantly improving its condition. Full article

Bioleaching, mediated by selected microflora, offers a more environmentally friendly and cost-effective alternative to traditional mining techniques by transforming metals from sulfide ores into water-soluble forms. Pyrite ores often contain valuable rare or noble metals, such as gold (Au), silver (Ag), nickel (Ni), and cobalt (Co), which can be leached through the metabolic activity of specific chemoautotrophic microorganisms. This study investigates the adaptation process of the Acidithiobacillus ferriphilus bacterial strain, originally isolated from acid mine drainage (AMD), for the bioleaching of pyrite. The progress of the bioleaching process was evidenced by the release of iron (3.6 mg/mL) and significant quantities of gold (0.21 mg/L, equivalent to 3 g/t) into the post-culture liquid. The results indicate that the most effective bioleaching was achieved during the final adaptation stage, utilizing a medium with 7% pyrite content and a 0.75% supplement of an easily accessible energy source in the form of iron sulfate. These findings confirm the potential of the A. ferriphilus strain for pyrite bioleaching. Full article

Antimicrobial materials are gaining significant interest as awareness of pathogens spread through contact becomes increasingly prevalent. While various compounds with antibacterial properties have been explored as active ingredients in such materials, many are prone to leaching, leading to undesirable risks to the environment and to human health. Herein, we develop and test a multilayered plastic film filled with silver nanoparticles, long known to be potent antibacterial agents, supported in a silica matrix. Cross-linked methacrylate layers on both sides of these nanostructures prevent leaching even after several uses, making the material essentially benign. Furthermore, we derive silica from rice husk, an abundant and affordable agricultural waste product. Our findings demonstrate that initial irradiation of the material with UVA light facilitates the photothermal migration of nanoparticles towards the material’s surface, thereby significantly enhancing its antimicrobial properties. Remarkably, after just 5 min of visible light irradiation, the material exhibits over 99.999% inhibition of bacterial growth. This environmentally friendly plastic composite harnesses visible light to actively combat bacteria, providing an exciting proof-of-concept for future applications in antimicrobial coatings. Full article