Search Results (72)

The rapid expansion of global aquaculture has led to wastewater enriched with nitrogen, phosphorus, organic matter, antibiotics, and heavy metals, posing serious risks such as eutrophication, ecological imbalance, and public health threats. Conventional physical, chemical, and biological treatments face limitations including high cost, secondary pollution, and insufficient efficiency, limiting sustainable wastewater management. Algal–bacterial symbiotic systems (ABSS) provide a sustainable alternative, coupling the metabolic complementarity of microalgae and bacteria for effective pollutant mitigation and concurrent biomass valorization. Immobilizing microbial consortia within carrier materials enhances system stability, tolerance to environmental changes, and scalability. This review systematically summarizes the pollution characteristics and ecological risks of aquaculture effluents, highlighting the limitations of conventional treatment methods. It focuses on the metabolic cooperation within ABSS, including nutrient cycling and pollutant degradation, the impact of environmental factors, and the role of immobilization carriers in enhancing system performance and biomass resource valorization. Despite their potential, ABSS still face challenges related to mass transfer limitations, complex microbial interactions, and difficulties in scale-up. Future research should focus on improving environmental adaptability, regulating microbial dynamics, designing intelligent and cost-effective carriers, and developing modular engineering systems to enable robust and scalable solutions for sustainable aquaculture wastewater treatment. Full article

Bottom sediments play a central role in regulating contaminant dynamics in aquatic systems. They act as both storage sites and reactive zones where contaminants undergo transformation, sequestration, or remobilization. Contaminants primarily enter sediments through anthropogenic activities, including agricultural runoff, industrial effluents, wastewater discharge, urban runoff, and mining operations. This review focuses on six major contaminant groups, including nutrients, heavy metals, pharmaceutical residues, pesticides, polycyclic aromatic hydrocarbons, and microplastics, and examines the mechanistic processes that govern their fate in sediments. The main mechanisms includesorption–desorption on minerals and organic materials, sedimentation, and redox processes that regulate metal immobilization and sulfide formation. The persistence and mobility of contaminants are also influenced by synergistic or antagonistic interactions among pollutants, microbial transformation of organic compounds, and oxidative degradation of microplastics by reactive oxygen species. Contaminants can affect benthic communities by causing toxic effects and oxygen depletion. They also may alter microbial and macrofaunal populations and contribute to bioaccumulation and biomagnification. Ultimately, these insights are important for predicting contaminant behavior and assessing ecological risks, which directly informs the development of effective environmental monitoring programs and sustainable sediment remediation strategies for the long-term protection of aquatic ecosystems. Full article

This study systematically explores the mechanisms and application potential of biochar in remediating heavy metal-contaminated soils. Particular emphasis is placed on the role of raw materials and pyrolysis conditions in modulating key physicochemical properties of biochar, including its aromatic structure, porosity, cation exchange capacity, and ash content, which collectively enhance heavy metal immobilization. The direct remediation mechanisms are categorized into six pathways: physical adsorption, electrostatic interactions, precipitation, ion exchange, organic functional group complexation, and redox reactions, with particular emphasis on the reduction in toxic Cr⁶⁺ and the oxidation of mobile As³⁺. In addition to direct interactions, biochar indirectly facilitates remediation by enhancing soil carbon sequestration, improving soil physicochemical characteristics, stimulating microbial activity, and promoting plant growth, thereby generating synergistic effects. The study evaluates combined remediation strategies integrating biochar with phytoremediation and microbial remediation, highlighting their enhanced efficiency. Moreover, practical challenges related to the long-term stability, ecological risks, and economic feasibility in field applications are critically analyzed. By synthesizing recent theoretical advancements and practical findings, this research provides a scientific foundation for optimizing biochar-based soil remediation technologies. Full article

Microbial spores are increasingly recognized as multifunctional platforms for enzyme immobilization, combining natural resilience with biotechnological versatility. Their inherent structural complexity enables high enzyme load, thermal and chemical stability, and robustness to be repeatedly used under industrially relevant conditions, largely widening their application scope. This review explores the growing role of spore-based systems in biocatalysis, from naturally active spores to engineered microbial hosts capable of producing immobilized enzymes in situ. Compared to conventional immobilization techniques, spore-based strategies offer simplified workflows, reduced environmental impact, and greater sustainability. Recent innovations also extend beyond traditional applications, introducing artificial spores and incorporating spores into biocomposite materials and biosensors. These developments reflect a shift from basic enzyme stabilization research toward scalable solutions in waste remediation, polymer degradation, green chemistry, and synthetic biology. Overall, spore-enabled biocatalysis represents a modular and robust toolset for advancing industrial biotechnology and sustainable manufacturing, instrumental in achieving a circular and bioeconomy. Full article

Poplar (Populus L. species), a fast-growing temperate species, forms plantations with high productivity and biomass, with its litter sustaining key functions in nutrient cycling, microbial diversity, and carbon storage. Litter microbial communities drive decomposition, particularly in early stages, this initial phase is characterized by the leaching of water-soluble carbon and nutrients from the litter, which creates a readily available resource pulse that facilitates rapid microbial colonization and activation. This process is followed by the activation of microbial enzymes and the immobilization of nutrients, collectively initiating the breakdown of more recalcitrant litter materials. Under rising global nitrogen deposition, we conducted a field randomized block experiment in 13-year-old pure poplar (Populus deltoides L. ‘35’) stands, with three nitrogen addition treatments: N0 (0 g N·m⁻²·yr⁻¹), N2 (10 g N·m⁻²·yr⁻¹), and N4 (30 g N·m⁻²·yr⁻¹). In the initial phase of litter decomposition, we measured the soil properties and litter traits, the litter microbial community composition, and its taxonomic and phylogenetic diversity indices. The results indicate that nitrogen addition altered microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), soil NO₃⁻-N, and accelerated litter decomposition rates. The microbial community in leaf litter responded to nitrogen addition with increased phylogenetic clustering (higher OTU richness and NRI), which suggests that environmental filtering exerted a homogenizing selective pressure linked to both soil and litter properties, whereas the microbial community in branch litter responded to nitrogen addition with increased taxonomic diversity (higher OTU richness, Shannon, ACE, and Chao1), a pattern associated with litter properties that likely alleviated nitrogen limitation and created opportunities for more taxa to coexist. The observed differences in response stem from distinct substrate properties of the litter. This study elucidates microbial taxonomic and phylogenetic diversity responses to nitrogen addition during litter decomposition, offering a scientific foundation for precise microbial community regulation and sustainable litter management. Full article

Pyrochar has been identified as a favorable soil conditioner that can effectively ameliorate soil acidification. Hydrochar is considered a more affordable carbon material than pyrochar, but its effect on the process of soil acidification has yet to be investigated. An indoor incubation and a soil column experiment were conducted to study the effect of rice straw hydrochar application on nitrification and NO₃⁻-N leaching in acidic red soil. Compared to the control and pyrochar treatments, respectively, hydrochar addition mitigated the net nitrification rate by 3.75–48.75% and 57.92–78.19%, in the early stage of urea fertilization. This occurred mainly because a greater amount of dissolved organic carbon (DOC) was released from hydrochar than the other treatments, which stimulated microbial nitrogen immobilization. The abundances of ammonia-oxidizing archaea and ammonia-oxidizing bacteria were dramatically elevated by 25.62–153.19% and 12.38–22.39%, respectively, in the hydrochar treatments because of DOC-driven stimulation. The cumulative leaching loss of NO₃⁻-N in soils amended with hydrochar was markedly reduced by 43.78–59.91% and 61.70–72.82% compared with that in the control and pyrochar treatments, respectively, because hydrochar promoted the soil water holding capacity by 2.70–9.04% and reduced the residual NO₃⁻-N content. Hydrochar application can dramatically diminish total H⁺ production from soil nitrification and NO₃⁻-N leaching. Thus, it could be considered an economical soil amendment for ameliorating soil acidification. Full article

Long-term monoculture of poplar plantations for industrial material production has been widely reported to cause severe soil degradation, while the presence of understory vegetation might enhance soil nitrogen (N) transformation and supply. This study employed a field experiment using a randomized block design with three blocks and four understory treatments, including understory removal, N-fixing species planting, single-species retention, and diverse vegetation retention, in poplar plantations on a mid-latitude alluvial plain in China over 6 years to assess the effects of different species and richness of understory on soil N transformation and related microbial traits via ¹⁵N assays and shotgun metagenomics. The results showed that understory removal significantly reduced soil N transformation rates, bacterial abundance, and gene abundance associated with N transformation. Compared to a single-species understory, retaining a diverse understory with high species richness significantly increased soil gross N transformation rate of mineralization by 149%, nitrification by 221%, and immobilization by 85%; comprehensively enriched dominant bacterial phyla; and elevated gene abundances of gdh_K15371, ureB, hao, and amoA_B associated with N transformation. No significant difference in N transformation rates existed between N-fixing species planting treatment and single-species retention treatment, while N-fixing species planting treatment specifically promoted the soil bacterial phyla Nitrospirae and Chloroflexi, and increased the gene abundances of gdh_K15371 and hao. These findings demonstrate that both introducing N-fixing species and an increase in species richness of the understory effectively promoted soil N transformation but that different underlying mechanisms existed. Planting N-fixing species selectively increased the soil bacterial phyla of Nitrospirae and Chloroflexi, whereas the increase in species richness broadly enriched soil bacterial diversity, thereby inducing the enrichment of the functional genes and enhancing soil N transformation. In conclusion, both planting N-fixing species and retaining diverse understory vegetation were effective strategies for maintaining sustainable management of poplar plantations by increasing soil N availability. Full article

Microbial remediation of Cr(VI)-polluted wastewater offers an effective and sustainable green method. In this study, a novel strain Priestia megaterium strain BM.1 that was capable of reducing Cr(VI) was domesticated. In order to improve its Cr(VI) reduction and adsorption performance, calcium-modified hydrochar (HC-Ca) was utilized to immobilize the strain to obtain the composite material BM.1-Ca. The BM.1-Ca composite achieved a Cr(VI) removal efficiency of 97% at an initial concentration of 60 mg/L within 60 h, representing a 1.96-fold enhancement compared to BM.1 alone and demonstrating significantly improved microbial Cr(VI) removal capacity. The addition of HC-Ca was instrumental in maintaining the stable Cr(VI) removal efficiency of BM.1 in the presence of altered incubation environments and interference from co-existing ions. The reduction in Cr(VI) by BM.1 and the immobilization of Cr(III) on the surface of BM.1-Ca are the main removal mechanisms of Cr(VI). Analysis of microbial oxidative stress and extracellular polymers showed that HC-Ca was able to attenuate the oxidative stress of BM.1 as well as promote the secretion of extracellular polymers. This study reveals the intrinsic mechanism of the novel material BM.1-Ca for remediation of Cr(VI) pollution in water bodies and provides an effective method for bioremediation of Cr(VI). Full article

This study investigates the enhancement of nitrogen removal performance in an intermittent biological sponge iron system (BSIS) through the immobilization of aerobic denitrifying bacteria. The aim is to improve the efficiency of simultaneous nitrification and denitrification (SND) in the BSIS by optimizing the microbial community involved in nitrogen conversion. The immobilization technique not only stabilizes the microbial activity and abundance of aerobic denitrifying bacteria, but also promotes a more efficient denitrification process. The optimal material ratio of polyvinyl alcohol–sodium alginate gel beads was determined as 10 g/100 mL PVA, 4 g/100 mL SA, 2 g/100 mL CaCl₂, and 2 g/100 mL of bacterial suspension, achieving a maximum NO₃⁻-N removal rate of 91.73%. A response surface model (RSM), established for the operational conditions, (shaker speed, temperature, and pH) showed a high fitting degree (R2 = 0.9960) and predicted the optimal conditions for maximum NO₃⁻-N removal as 109.24 rpm, 23.6 °C, and pH 7.9. Compared to R1 (47.82%), R3 achieved a higher average total nitrogen (TN) removal rate of 95.49%, following the addition of immobilized aerobic denitrifying bacteria to the BSIS. Full article

Amperometric biosensors (ABSs) and enzymatic biofuel cells (BFCs) share several fundamental principles in their functionality, despite serving different primary purposes. Both devices rely on biorecognition, redox reactions, electron transfer (ET), and advanced electrode materials, including innovative nanomaterials (NMs). ABSs and BFCs, utilizing microbial oxidoreductases in combination with electroactive NMs, are both efficient and cost-effective. In the current study, several laboratory prototypes of BFCs have been developed with bioanodes based on yeast flavocytochrome b₂ (Fcb₂) and alcohol oxidase (AO), and a cathode based on fungal laccase. For the first time, BFCs have been developed featuring anodes based on Fcb₂ co-immobilized with redox NMs on a glassy carbon electrode (GCE), and cathode-utilizing laccase combined with gold–cerium–platinum nanoparticles (nAuCePt). The most effective lactate BFC, which contains gold–hexacyanoferrate (AuHCF), exhibited a specific power density of 1.8 µW/cm². A series of BFCs were developed with an AO-containing anode and a laccase/nAuCePt/GCE cathode. The optimal configuration featured a bioanode architecture of AO/nCoPtCu/GCE, achieving a specific power density of 3.2 µW/cm². The constructed BFCs were tested using lactate-containing food product samples as fuels. Full article

Widespread use of pesticides in agriculture causes adverse impacts on non-target organisms and environmental pollution. Efficient and sustainable pesticide removal alternatives must be developed to reduce pesticide environmental impacts. Recently, bioremediation based on immobilized microorganisms has been proposed as an environmentally friendly and cost-effective approach for pesticide degradation in water. Agro-industrial wastes are produced in large quantities in crop fields; their high availability, low cost, and potential for reuse make them ideal support materials for microbial immobilization. This systematic review, conducted through the PRISM 2020 methodology, compiles recent research on using agro-industrial waste to immobilize microorganisms for pesticide degradation. The identified studies highlight corn straw as the most studied agro-industrial waste, while the organophosphorus insecticides, chlorpyrifos, and methyl parathion were the most representative pesticides; in the identified studies, pesticide degradation was conducted mainly by bacteria of the Acinetobacter, Bacillus, and Pseudomonas genera. Overall, microbial immobilization significantly enhanced pesticide degradation, rendering it a viable bioremediation strategy for pesticide-contaminated water. Full article

Microbial-induced carbonate precipitation technology allows concrete to detect and diagnose cracks autonomously. However, the concrete’s compact structure and alkaline environment necessitate the adoption of a proper carrier material to safeguard microorganisms. In this study, various bacterial strains, including Bacillus subtilis, Bacillus sphaericus, and Bacillus megaterium, were immobilized in lightweight expanded clay aggregates (LECA) to investigate their effect on the self-healing performance, mechanical strength, and freeze–thaw durability. Self-healing concrete specimens were prepared using immobilized LECA, directly added bacterial spores, polyvinyl acetate (PVA) fibers, and air-entraining admixture (AEA). The pre-cracked prisms were monitored for 224 days to assess self-healing efficiency through ultrasonic pulse velocity (UPV) and surface crack analysis methods. A compressive strength restoration test was conducted by pre-loading the cube specimens with 60% of the failure load and re-testing them after 28 days for strength regain. Additionally, X-ray diffraction and scanning electron microscopy (SEM) were conducted to analyze the precipitate material. The findings revealed that self-healing efficiency improved with the biomineralization activity over the healing period demonstrated by the bacterial strains. Compression and flexural strengths decreased for the bacterial specimens attributed to porous LECA. However, restoration in compression strength and freeze–thaw durability significantly improved for the bacterial mixes compared to control and reference mixes. XRD and SEM analyses confirmed the formation of calcite as a self-healing precipitate. Overall, results indicated the superior performance of Bacillus megaterium followed by Bacillus sphaericus and Bacillus subtilis. The findings of the current study provide important insights for the construction industry, showcasing the potential of bacteria to mitigate the degradation of concrete structures and advocating for a sustainable solution that reduces reliance on manual repairs, especially in inaccessible areas of the structures. Full article

Although bioremediation is considered the most environmentally friendly and sustainable technique for remediating contaminated soil and water, it is most effective when combined with physicochemical methods, which allow for the preliminary removal of large quantities of pollutants. This allows microorganisms to efficiently eliminate the remaining contaminants. In addition to requiring the necessary genes and degradation pathways for specific substrates, as well as tolerance to adverse environmental conditions, microorganisms may perform below expectations. One typical reason for this is the high toxicity of xenobiotics present in large concentrations, stemming from the vulnerability of bacteria introduced to a contaminated site. This is especially true for planktonic bacteria, whereas bacteria within biofilms or microcolonies have significant advantages over their planktonic counterparts. A physical matrix is essential for the formation, maintenance, and survival of bacterial biofilms. By providing such a matrix for bacterial immobilization, the formation of biofilms can be facilitated and accelerated. Therefore, bioremediation combined with bacterial immobilization offers a comprehensive solution for environmental cleanup by harnessing the specialized metabolic activities of microorganisms while ensuring their retention and efficacy at target sites. In many cases, such bioremediation can also eliminate the need for physicochemical methods that are otherwise required to initially reduce contaminant concentrations. Then, it will be possible to use microorganisms for the remediation of higher concentrations of xenobiotics, significantly reducing costs while maintaining a rapid rate of remediation processes. This review explores the benefits of bacterial immobilization, highlighting materials and processes for developing an optimal immobilization matrix. It focuses on the following four key areas: (i) the types of organic pollutants impacting environmental and human health, (ii) the bacterial strains used in bioremediation processes, (iii) the types and benefits of immobilization, and (iv) the immobilization of bacterial cells on various carriers for targeted pollutant degradation. Full article

Herein, biochars derived from corn stalks, rice husks, and bamboo powder were modified by nitric acid oxidation and sodium hydroxide alkali activation to identify efficient and cost-effective polycyclic aromatic hydrocarbon-adsorbent and microbial-immobilized carriers. The surface characterization and adsorption investigation results suggested that acid/alkali modification promoted the phenanthrene removal ability in an aqueous solution of biochars via facilitating π–π/n–π electron donor–acceptor interactions, electrostatic interactions, hydrogen bonds, and hydrophobic interactions. Subsequently, the degrading bacteria Rhodococcus sp. DG1 was successfully immobilized on the rice husk-derived biochar with nitric acid oxidation (RBO), which exhibited the maximum phenanthrene adsorption efficiency (3818.99 µg·g⁻¹), abundant surface functional groups, and a larger specific surface area (182.6 m²·g⁻¹) and pore volume (0.141 m³·g⁻¹). Degradation studies revealed that the microorganisms immobilized on RBO by the adsorption method yielded a significant phenanthrene removal rate of 80.15% after 30 days, which was 38.78% higher than that of the control. Conversely, the polymer gel network-based microenvironment in the microorganism-immobilized RBO by the combined adsorption–embedding method restricted the migration and diffusion of nutrients and pollutants in the reaction system. This study thus introduces an innovative modified biochar-based microbial immobilization technology characterized by a simple design, convenient operation, and high adsorption efficiency, offering valuable insights into material selection for PAH contamination bioremediation. Full article

The processes of coal mining and washing generate a substantial amount of coal gangue. During prolonged outdoor storage, this waste can lead to both direct and indirect environmental pollution, as well as geological hazards. Recent research has indicated that the redox processes of coal gangue are regulated by microorganisms. Techniques such as the application of biocides and the facilitation of microbial interactions have proven effective in controlling the acidic pollution of coal gangue in the short term. However, conventional doping methods that couple sulfate-reducing bacteria with biocides face challenges, including a short effective duration and poor stability. To address these issues, this study utilized corn straw biochar as a microbial attachment material and incorporated water-retaining agents as slow-release biocide carriers, resulting in the development of an environmentally friendly microbial remediation material. This study selected 0.6 g of biochar produced from the pyrolysis of corn straw at 700 °C to immobilize sulfate-reducing bacteria. Additionally, 0.6 g of polyacrylamide was used to prepare a slow-release bactericide with 100 mL of a sodium dodecyl sulfate solution at a concentration of 50 mg·L⁻¹. The composite remediation material successfully raises the pH of weathered coal gangue leachate from 4.32 to 6.88. Its addition notably reduces the sulfate ion concentration in the weathered coal gangue, with sulfate content decreasing by 86.45%. Additionally, the composite material effectively lowers the salinity of the weathered coal gangue. The composite immobilizes heavy metal ions within the weathered coal gangue, achieving an approximate removal rate of 80% over 30 days. Following the introduction of the composite material, significant changes were observed in the dominant microbial communities and population abundances on the surface of the coal gangue. The composite demonstrated the ability to rapidly, sustainably, and effectively remediate the acidification pollution associated with coal gangue. Full article