Bacterial community structure and function are key determinants of antibiotic resistome dynamics. Although sulfur metabolism has been shown to modulate antibiotic resistance, its role in shaping the resistome within sulfate-reducing bacteria (SRB) remains poorly understood. Here, we used metagenomic sequencing to characterize the antibiotic resistome in SRB enriched from uranium-mining impacted soils and adjacent river sediments. Among the 343 subtypes of antibiotic resistance genes (ARGs) across 19 types, multidrug resistance genes were found to dominate SRB communities, particularly in the genus Desulfovibrio. Uranium mining stress markedly increased the abundance of plasmid by up to 259-fold, thereby enhancing the mobility of the antibiotic resistome in SRB. Additionally, a significant positive correlation was observed between sulfur-metabolic genes (e.g., dmsA/B) and ARGs (p < 0.01), suggesting a robust linkage between sulfur metabolism and the antibiotic resistome. Furthermore, the frequent co-occurrence of ARGs and heavy metal resistance genes on plasmids evidenced their co-selection via plasmid-mediated transfer in SRB. Collectively, our findings establish SRB as critical hubs for ARGs propagation in uranium mining areas, offering valuable insights for the risk assessment and management of emerging contaminants in heavy metal-impacted ecosystems.

Landfill leachate is a high-strength wastewater generated during municipal solid-waste disposal, and its composition and biodegradability vary strongly with landfill age. Dissolved organic matter (DOM) constitutes the dominant organic pool in leachate and influences treatment efficiency, toxicity, contaminant complexation, membrane fouling, concentrate management, and process sustainability. Recent ultrahigh-resolution mass spectrometry, especially Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS), combined with multidimensional spectroscopy, enables molecular-level characterization of leachate DOM and tracking of its evolution during landfill aging and treatment. This review synthesizes molecular-level evidence on leachate DOM evolution, transformation, and engineering regulation within a molecular evolution–process selectivity–engineering regulation framework. Available evidence indicates that, during landfill aging, leachate DOM shifts from protein- and aliphatic-enriched mixtures toward a more oxygenated, aromatic, heteroatom- or halogen-bearing, and persistent pool, and this age-dependent evolution underlies declining biodegradability and reshapes process selectivity. We further synthesize process-selective DOM behaviors across physicochemical separation, advanced oxidation, and biological conversion, and highlight paired mass differences-based reactionomics and interpretable machine learning to link molecular fingerprints with transformation pathways and key operational metrics. Finally, we highlight the need to clarify DOM–microbial interactions, reduce method-related biases, and translate molecular descriptors into practical monitoring and operating conditions. Overall, this review argues for moving leachate treatment beyond bulk-metrics-based process stacking toward molecularly informed treatment-train design under stringent discharge limits and management strategies directed toward zero liquid discharge.

The interaction between microplastics (MPs) and heavy metals in aquatic environments is well-documented to be modulated by coexisting ions. However, the impact of coexisting ions on the interaction between radioactive heavy metal and MPs at the atomic scale remains poorly understood. This study explored the mechanisms by which coexisting ions affect cesium (Cs+) adsorption on MPs through integrated batch adsorption experiments, characterization techniques, and density functional theory calculations. Our results demonstrate that, compared to pure water systems, polystyrene (PS) MPs exhibited significantly enhanced Cs+ adsorption capacity in simulated seawater (by up to 1.76 times), with NaCl identified as the primary contributor. Kinetic and isotherm models further revealed that NaCl significantly boosts Cs+ adsorption by PS MPs without altering the underlying physical multilayer adsorption mechanism. Surface characterization analysis indicated that NaCl can increase the adsorption sites for Cs+ by enhancing the surface roughness of PS MPs. Spectroscopic analysis suggested that the benzene rings of PS MPs play an important role in the Cs+ adsorption process. Density functional theory calculations further elucidated that the enhanced Cs+ adsorption capacity onto the benzene rings of PS MPs primarily stems from NaCl-induced amplification of dispersion (van der Waals), electrostatic, and particularly polarization effects. These findings provide first atomistic view of seawater ion-facilitated Cs+ adsorption on MPs, offering critical theoretical support for the ecological risk assessment of co-occurring MPs and radionuclides in marine ecosystems.

Microplastic (MP) biodegradation is critical for mitigating plastic pollution, yet the ecological mechanisms linking polymer properties to plastisphere microbiome assembly and catalytic function remain unclear. Using thermophilic composting as an accelerated model, we reveal a fundamental dichotomy in which biodegradable MPs (BMPs: polylactic acid [PLA] > polybutylene succinate [PBS] > poly (butylene adipate-co-terephthalate) [PBAT]) undergo rapid thermophilic degradation shaped by stronger environmental filtering of diverse degraders, whereas conventional MPs (CMPs: low-density polyethylene [LDPE]) exhibit delayed degradation with greater stochastic influence. Metagenomics uncovered 489 degradative genes predominantly distributed across uncultured taxa, enabling reconstruction of polymer-specific multi-enzyme pathways, supported by isolating 32 potential degraders (31 candidate novel). PLA/PBS degradation primarily relied on thermophilic-phase PLA depolymerase and cutinase, PBAT on late-stage polyesterase and PETase, and LDPE on alkane monooxygenase and laccase. Statistical modelling showed BMP degradation strongly associated with plastisphere-physicochemical interactions (> 90% variance), whereas CMP appeared primarily constrained by material properties (e.g., degrader succession in PLA, enrichment in PBS/PBAT, and high molecular weight in LDPE). Functionally dominant degraders (1.9% of total microbes) were estimated to contribute 52.4%-80.6% of biodegradation efficiency. This work elucidates the core polymer-plastisphere-functional nexus underlying MP biodegradation during composting, providing a predictive framework and microbial resource for targeted remediation.

Microplastics in aquatic environments facilitate the formation of specific plastisphere microbiomes and serve as potential hotspots for antibiotic resistance genes (ARGs) propagation. However, the systematic comparisons of ARG profiles on microplastics from different aquatic ecosystems remain limited, particularly the prevalent ARGs and their bacterial hosts. This study performed a comparative meta-analysis of existing metagenomic datasets to investigate the resistome between freshwater and seawater microplastics (FMP and SMP) and their driving factors. Our results revealed that the ARG profiles on both FMP and SMP were significantly distinct from their surrounding waterbody. Moreover, FMP exhibited a higher diversity and abundance of ARGs rather than SMP. Ten core ARGs were shared on FMP and SMP, while 23 core ARGs were exclusively detected on FMP. The bacterial community on microplastics exhibited an ecosystem-specific composition, and was identified as the primary determinant shaping the ARG profiles. Notably, more complex bacteria-ARG co-occurrence pattern was identified on FMP, involving a broader spectrum of core genera and potential pathogenic hosts (e.g., Mycobacterium, Streptomyces). Furthermore, a significant and specific correlation between mobile genetic elements and ARGs was identified on FMP but not SMP, suggesting a markedly elevated horizontal gene transfer potential, with mechanistic support from the concurrent enrichment of oxidative stress and SOS response genes on FMP. These findings provide a comprehensive characterization of ARGs on aquatic microplastics, and especially highlight the role of FMP in the ARG dissemination.

The plastisphere, the biofilm community on plastic debris, is recognized as a reservoir for antibiotic resistance genes (ARGs) and pathogens. However, the comparative risks of biodegradable (BPs) versus non-biodegradable (non-BPs) plastics remain unclear. This study tested the hypothesis that BPs and non-BPs foster distinct risk trajectories through distinct underlying mechanisms. We investigated microbial succession and the fate of ARGs and virulence factors (VFs) on polylactic acid (PLA, one of the BPs), polyvinyl chloride (PVC), and polystyrene (PS) during an 88-day in situ incubation in a tidal river. Metagenomic analysis revealed that PVC consistently harbored the highest abundance of ARGs and mobile genetic elements (MGEs), acting as a persistent hub for resistance, with multidrug resistance genes enriched up to 3.5-fold compared with river water. In contrast, the biodegradable PLA exhibited a distinctly transient risk profile during the mid-degradation stage, creating a hotspot for opportunistic pathogenic genera like Vibrio and Acinetobacter, coinciding with a significant spike in ARGs' abundance. Genome-resolved metagenomics further confirmed the co-localization of ARGs and VFs within high-risk metagenome-assembled genomes (MAGs). These findings demonstrate that both BPs and non-BPs pose significant but fundamentally different risks of ARGs and VFs. Risk assessments must therefore consider the entire lifecycle of plastics, accounting for the transient, degradation-driven hazards posed by BPs and the persistent, accumulative threats posed by non-BPs.

This study investigated the effects of different doses of biogas residue biochar (BRB) (5 g /L and 10 g/L) on the methanogenic performance and metabolic pathways during anaerobic digestion (AD) of food waste (FW) under a wide range of organic loading rate (OLR) (5, 10, 20, and 30 g volatile solid (VS)/L) conditions. The results indicated the cumulative methane yield was highest (375 +/- 8.40 mL/g VS) at an OLR of 10 g VS/L when no BRB was added, while suffered significant inhibition at higher OLRs (>10 g VS/L) due to volatile fatty acid (VFA) accumulation. BRB addition (5 g/L) significantly facilitated methane production by first enhancing organic matter degradation and VFA content (days 1---10), and then accelerating VFA consumption (days 18---50), with these beneficial effects becoming progressively more pronounced at higher OLRs (>5 g VS/L) in this study. Microbial and metabolic analysis revealed key microbial communities included Aminobacterium, Proteiniphilum, Clostridium_sensu_stricto_1, Syntrophomonas, and Methanosarcina were enriched, and methanol and methylamine/ dimethylamine/trimethylamine methanogenic pathways were enhanced under high OLR conditions with BRB addition. This study provides metabolic flexibility for maintaining stable methane production in response to high OLR while offering a closed-loop solution for digestate valorization.

Chain elongation (CE) is an effective strategy for converting organic wastes into value-added medium-chain fatty acids (MCFAs), wherein electron donors (EDs) dictate process efficiency. However, beyond substrate toxicity and limited reducing power, conventional EDs such as ethanol and lactate impose a chronic bioenergetic constraint: their minimal net ATP yield thermodynamically restricts CE strictly to the energy-neutral reverse β-oxidation (RBO) pathway. To overcome this bioenergetic bottleneck, this study investigated fructose as a high-energy-yielding multidimensional ED to drive n-caproate production from food waste in a mixed-culture system. Herein, the results demonstrated a dose-dependent enhancement of n-caproate, peaking at 12.38 g/L with a remarkable selectivity of 63.0 % (50 g/L fructose dosage). Mechanistically, fructose fermentation established an in-situ synergistic multi-ED microenvironment (fructose, ethanol, and lactate) that buffered toxicity and sustained robust reducing power. More critically, intensive glycolytic flux induced a hyper-energetic intracellular state characterized by abundant ATP and elevated NADH/NAD⁺ ratio. Meanwhile, the activities of key enzymes (e.g., phosphofructokinase and butyrate kinase) were significantly stimulated, redirecting carbon flow toward butyrate and n-caproate. This favorable energetic and metabolic environment further selectively enriched Limosilactobacillus spp., which glycolyzed fructose into essential carbon intermediates for CE. Finally, metagenomic profiling revealed that the fructose-induced ATP surplus profoundly enriched genes associated with the ATP-dependent fatty acid biosynthesis (FAB), while suppressing RBO-related genes. This uncovers a paradigm shift from the RBO-dominated route to a FAB-driven mechanism. These findings unravel how a targeted carbohydrate structurally rewires the thermodynamic hierarchy of CE pathways, providing novel mechanistic blueprints for upgrading complex organic wastes into high-value biochemicals.

Conjugative transfer of antibiotic resistance genes (ARGs) in aquatic environments severely exacerbates global health risks. While iron (oxyhydr)oxide minerals are well known to regulate ARGs conjugative transfer in bacteria, the roles of reduced iron minerals remain poorly understood. Here we demonstrate that low concentrations (25-50 mg/L) of nano-FeS improve ARGs transfer efficiency by up to 707.12 %. Nano-FeS and its oxidation-derived species, including extracellular reactive oxygen species (ROS), Fe2+, and mineral particles, trigger intracellular ROS production to initially strengthen bacterial adhesion. These factors further increase cell membrane permeability via physicochemical damage, thereby promoting plasmid transmembrane transfer. Meanwhile, moderate ROS accumulation also upregulates plasmid transport gene expression and provides metabolic energy for conjugation. Beyond these dominant physiological/biochemical responses, mineral particles bridge adjacent bacteria to facilitate intercellular contact. In contrast, high nano-FeS dosage (500 mg/L) reduces conjugation efficiency by 42.19 %-79.29 %. Nano-FeS and its oxidation-derived species impair cell adhesion and energy metabolism by inducing excessive intracellular ROS, and cause lethal membrane damage. Moreover, mineral particles exert a prominent coating effect that ultimately inhibits conjugative transfer. Notably, this bidirectional regulatory effect is consistently observed across various real aquatic matrices including paddy field pore water and pond bottom water. Our findings highlight that reduced iron minerals serve as redox-sensitive "switches" governing ARGs conjugation, providing new insights into iron chemistry for mitigating ARGs propagation in engineered and natural environments.

Nano zero-valent iron (nZVI) has emerged as an inorganic electron donor for denitrification in low carbon‑to‑nitrogen (C/N) wastewater, but its low electron utilization efficiency and nanotoxicity limit practical implementation. Inspired by microbial self-protection mechanisms, a robust bio-nano interface was engineered by coating nZVI with extracellular polymeric substances (EPS) from Shewanella oneidensis MR-1 (EPS@nZVI). The EPS@nZVI microbial combined system achieved 97.6% nitrate removal at a C/N ratio of 2, significantly outperforming systems with bare nZVI (60.2%). Mechanistically, the EPS coating served a dual function by acting as a redox-active "geobattery" while mitigating nZVI-induced nanotoxicity. By buffering electrons from rapid Fe⁰ corrosion, the EPS synchronized abiotic electron release with microbial uptake, redirecting electrons from hydrogen evolution to efficient biological utilization. Meanwhile, the EPS corona functions as a biocompatible shield that mitigates oxidative stress and membrane damage, thereby maintaining a metabolically active microbial community and foundational carbon metabolism. Multi-omics analyses revealed that EPS@nZVI selectively enriched electroactive taxa such as Geobacter, upregulated extracellular electron transfer and denitrification pathways, and reprogrammed microbial metabolism from stress response toward efficient energy harvesting. Collectively, the enhanced extracellular electron transfer efficiency and biocompatibility enabled by EPS@nZVI jointly governed the improved nitrate-reduction performance. This work demonstrates a bio-inspired strategy to rationally design nanomaterials that bridge the nano-bio interface, synchronizing abiotic electron supply with microbial metabolism for environmental remediation.

Valorizing food waste (FW) into medium-chain fatty acids (MCFAs) is a promising carbon-neutral technology, yet its industrial application is hampered by low electron transfer efficiency and poor long-term process stability. This study systematically investigated the efficacy and mechanisms of zero-valent iron (ZVI) and ferroferric oxide (Fe3O4) in enhancing caproic acid production from FW, with a focus on transitioning from batch optimization to sequencing batch operation. Batch experiments identified optimal dosages of 20 g/L for ZVI and 5 g/L for Fe3O4, boosting MCFA yields from non-detectable levels in the control (<2.5 mg COD/L) to 2.58 & times; 104 and 2.43 & times; 104 mg COD/L, respectively, with caproic acid accounting for 83.68% and 87.24%. Compared to batch mode, a sequential operation strategy involving sludge recycling demonstrated superior performance and increased MCFA yields by up to 53.2% and selectivity by 20.1%, as well as the dramatically shorted fermentation lag phase by 71%. Mecanistic analysis revealed that sequencing batch operation fostered a robust microbial consortium by progressively enriching key chain-elongating bacteria (e.g., Clostridia, Bacilli) and auxiliary hydrolytic/detoxifying microbes (e.g., Actinomycetes). This synergistic microbial community enhanced substrate conversion and system resilience. This work demonstrates a feasible strategy for achieving stable, efficient, and rapid start-up of caproic acid production from FW, and provides critical insights for its practical engineering application.

Microplastics (MPs) are known to host dense microbial biofilms and form the plastisphere, which serve as significant sites for various biogeochemical processes, including nitrogen transformation. The communication within these complex microbial communities is facilitated by quorum sensing (QS) signals. However, how this inter-bacteria signal crosstalk impacts the colonization and function of key microbes, such as denitrifiers, remains inadequately elucidated. This research delves into the impact of the external signaling molecule N-3-oxododecanoyl-L-homoserine lactone (C12-oxo-HSL) on biofilm development and denitrification processes by the model bacterium Paracoccus denitrificans (P. denitrificans) on microplastic surfaces. Treatment with 10 μM C12-oxo-HSL increased biofilm biomass 2.67-fold and nitrate removal rates 2.61-fold relative to controls, while planktonic biomass remained comparable to or lower than untreated samples, refuting the hypothesis that increased biofilm mass merely reflects accelerated planktonic growth. Transcriptomic analysis unveiled a sophisticated regulatory network. C12-oxo-HSL not only stimulated the expression of genes involved in initial adhesion and motility but also orchestrated a substantial upregulation of key energy metabolism pathways, including glycolysis, the tricarboxylic acid (TCA) cycle, and oxidative phosphorylation. Metabolic upregulation likely increased ATP availability for the augmented production of extracellular polymeric substances, ultimately leading to the formation of a more resilient and efficient biofilm structure. Our findings suggest a potential energy-centric mechanism where exogenous AHLs prime the cellular bioenergetic status to support the structural and functional demands of plastisphere colonization. This highlights the pivotal role of signal-mediated resource allocation in shaping the biogeochemical impact of microplastic pollution.

Microplastics (MPs) are pervasive contaminants in organic waste streams destined for anaerobic digestion (AD), yet their net effect on resource recovery remains a contentious issue with contradictory findings. To resolve this ambiguity, we conducted a robust three-level random-effects meta-analysis, synthesizing data from 55 studies, for disentangling the product-specific impacts of MPs on AD performance. Our analysis revealed that MPs shift carbon flow within AD: they suppress methanogenesis (-6.29% methane yield) while promoting acidogenesis (+23.73% total VFAs), with propionic, butyric, and valeric acids increasing by 12.74%, 14.55%, and 22.18%, respectively. This demonstrates that MPs do not simply inhibit AD but rather redirect its carbon flow, and this carbon rerouting is determined by polymer type. The effects of MPs on AD process could be conceptualized as novel hypothetical "Toxic Stress vs. Substrate Perturbation" models. Conventional polymers (e.g., polyvinyl chloride, polyethylene terephthalate) exert toxic stress, inhibiting methanogens and causing upstream VFA accumulation. Conversely, biodegradable polymers (e.g., polylactic acid, polybutylene adipate terephthalate) act as slow-release carbon sources, perturbing substrate availability to enhance methanogenesis. Furthermore, these effects are strongly modulated by MP concentration, size, and operational conditions like temperature, which can even reverse the inhibitory effects. This study reframes MPs from being simple inhibitors to active biogeochemical agents within engineered ecosystems. By clarifying MPs' product-specific effects, this study provides theoretical foundation of MPs affecting AD process, improving resilience and efficiency of AD-based resource recovery.

Food waste (FW) is a significant source of antibiotic resistance genes (ARGs) and anaerobic digestion is an effective strategy to limit the spread of antimicrobial resistance. In this study, ARGs diversity and abundance, along with their relationship to the microbial community were investigated by metagenomic and qPCR during thermophilic anaerobic co-digestion of FW, kitchen waste (KW) and garden waste (GW). Results indicate that R FK (FW + KW) and R FG (FW + GW) effectively reduced 9 and 13 representative ARG subtypes (removal rates exceeding 1 log unit), and completely eliminated 16 and 30 ARG subtypes, respectively, outperforming RF (FW). The Redundancy analysis indicated positive correlations between ARG removal rates and methane content, and negative correlations with volatile short-chain fatty acids and ammonia nitrogen. Procrustes and network centrality analyses suggested that removing resistant bacteria like Firmicutes and Bacteroidota in R FK and R FG contributed to efficient ARG removal. Co-digestion enhanced ARG elimination by improving reactor performance and altering bacterial communities.

The marine environment is grappling with microplastic (MP) pollution, necessitating an understanding of its distribution patterns, influencing factors, and potential ecological risks. However, the vast area of the ocean and budgetary constraints make conducting comprehensive surveys to assess MP pollution impractical. Interpretable machine learning (ML) offers an effective solution. Herein, we used four ML algorithms based on MP data calibrated to the size range of 20-5000 μm and considered various factors to construct a robust predictive ML model of marine MP distribution. Interpretation of the ML model indicated that biogeochemical and anthropogenic factors substantially influence global marine MP pollution, while atmospheric and physical factors exert lesser effects. However, the extent of the influence of each factor may vary within specific marine regions and their underlying mechanisms may differ across regions. The predicted results indicated that the global marine MP concentrations ranged from 0.176 to 27.055 particles/m3 and that MPs in the 20-5000-μm size range did not pose a potential ecological risk. The interpretable ML framework developed in this study covered MP data preprocessing, MP distribution prediction, and interpretation of the influencing factors of MPs, providing an essential reference for marine MP pollution management and decision making.

Azo dyes in textile wastewater present treatment challenges due to their structural complexity and resistance to biodegradation. While anaerobic digestion offers potential for azo dye degradation, its efficiency is limited by slow reaction kinetics and electron transfer constraints. This study demonstrated that nano zero-valent iron (nZVI) overcame these limitations through synergistic chemical and biological mechanisms. Using reactive orange 16 (RO16) as a representative azo dye, our results demonstrated that at the optimal concentration of 0.5 g/L, nZVI enhanced both RO16 degradation (98.4 % removal efficiency) and methane production (18.2 % increase) through chemical-biological synergy. First, nZVI rapidly cleaved azo bonds through chemical reduction, generating more biodegradable intermediates (2-phenylamine-5-nitrobenzenesulfonic acid and 4-vinylbenzenesulfonamide), thereby providing favorable substrates for subsequent microbial metabolism. Meanwhile, nZVI elevated the electron transfer system activity by up to 200 % and stimulated the production of humic acid-like substances, which functioned as electron shuttles to enhance direct interspecies electron transfer (DIET). At the community level, nZVI induced the enrichment of electroactive Georgenia (for dye degradation) by 99.9 % and DIET-capable methanogens by 55.8 %. Further gene expression analysis confirmed that nZVI upregulated critical functional genes, including those involved in acidogenic (phbB, 1.6-fold) and methanogenic (hmd, 1.7-fold) pathways, along with ABC transport genes (wzt, 1.2-fold) that potentially enhanced heme-dependent azoreductase production (hemH, 1.5-fold). Most remarkably, nZVI upregulated key electron transfer-related genes, particularly cytochrome oxidases (coxAC, 2.6-fold) and quinone biosynthesis (ubiC, 5.1-fold), thereby establishing a continuous conversion pathway from RO16 to methane. However, the beneficial effects of nZVI exhibited a concentration threshold, as elevated dose led to physical obstruction, reactive oxygen species overproduction (catE, 1.6-fold), and severe motility suppression, ultimately inhibiting methanogenesis. These insights advance fundamental understanding of bio-nano interactions in anaerobic environments and provide practical guidelines for implementing nZVI-enhanced treatment of refractory industrial wastewater.

Biodegradable plastics (BDPs) are an eco-friendly alternative to traditional plastics in organic waste, but their microbial degradation and impact on antibiotic resistance genes (ARGs) transmission during co-composting remain poorly understood. This study examines how alkaline-thermal pretreatment enhances BDPs degradation and influences the fate of ARGs and mobile genetic elements (MGEs) in co-composting. Pretreatment with 0.1 mol/L NaOH at 100℃ for 40 minutes increased the surface roughness and hydrophilicity of BDPs while reducing their molecular weight and thermal stability. Incorporating pretreated BDPs film (8 g/kg-TS) into the compost reduced the molecular weight of the BDPs by 59.70 % during the maturation stage, facilitating compost heating and prolonging the thermophilic stage. However, incomplete degradation of BDPs releases numerous smaller-sized microplastics, which can act as carriers for microorganisms, facilitating the dissemination of ARGs across environments and posing significant ecological and public health risks. Metagenomic analysis revealed that pretreatment enriched plastic-degrading bacteria, such as Thermobifida fusca, on BDPs surfaces and accelerated microbial plastic degradation during the thermophilic stage, but also increased ARGs abundance. Although pretreatment significantly reduced MGEs abundance (tnpA, IS19), the risk of ARGs dissemination remained. Three plastic-degrading bacteria (Pigmentiphaga sp002188465, Bacillus clausii, and Bacillus altitudinis) were identified as ARGs hosts, underscoring the need to address the risk of horizontal gene transfer of ARGs associated with pretreatment in organic waste management.

This study systematically evaluated the efficacy of feedstock-derived biochars (maize straw, rice husk, bamboo) in mitigating polystyrene microplastic (PSMP)-induced inhibition of food waste anaerobic digestion performance and antibiotic resistance gene (ARG) dissemination. Biochar addition increased cumulative methane production by 4.3%-8.3% and reduced total ARG absolute abundance by 35.5%-72.1%. Maize straw-derived biochar demonstrated superior mitigation capacity, attributed to its elevated specific surface area, functional group density, and electrical conductivity compared to other biochar. Mechanistically, biochar alleviated PSMP-induced inhibition of organic conversion and acid accumulation through metabolic pathway enhancement. Biochar enhanced methanogenesis by facilitating direct interspecies electron transfer and enriching diverse methanogenic archaea, thereby promoting metabolic pathway diversification. Additionally, biochar reduced ARG abundance through direct adsorption, reactive oxygen species suppression, selective inhibition of potential host bacteria, and horizontal gene transfer interference. This study confirmed that biochar addition simultaneously mitigates PSMP-induced suppression of methanogenesis and ARG propagation while elucidating the underlying mechanisms.

The bioconversion of food waste by black soldier fly larvae (BSFL) has garnered increased attention in recent years. However, nutrient-rich BSFL frass produced after larval harvesting does not meet the standard for organic fertilizer and requires secondary composting. This study investigated the co-composting of BSFL frass with different types of pig manure, including fresh (FR) and stored for 10 days (FM), to explore the microbial mechanisms enhancing humification and nitrogen retention using rice bran as a bulking agent. Results indicated FM achieved the longest thermophilic phase, exceeding 50 °C for 15 days and 55 °C for 8 days, along with the highest germination index (64.41 ± 2.13 %) and nitrogen content (4.09 ± 0.21 %). Ultraviolet-visible (UV-Vis) spectroscopy results demonstrated that FM facilitated the most effective humification process, with three-dimensional fluorescence spectrometer (3D-EEM) analyses confirming a greater humic acid formation. Microbial profiling revealed a predominant bacterial succession, with key populations including Bacillus spp., Micrococcales, Saccharomonospora, and uncultured Sphingobacteriaceae. Functional predictions based on PICRUSt2 analysis indicated nitrogen assimilation and fixation were enhanced, while denitrification was suppressed, thereby minimizing nitrogen loss. This study provides a viable strategy for integrating insect-based bioconversion with livestock manure composting to achieve high-value organic waste recycling.

Microplastics (MPs) are emerging pollutants that play an important role in the spread of highly toxic heavy metals. Although the pH has been shown to exert a substantial impact on the adsorption capacity of MPs towards heavy metals, the intricate mechanisms underlying how pH functions in the adsorption of radioactive heavy metals by MPs remain largely elusive. Here, we combined batch experiments and density functional theory calculations to investigate the adsorption behavior of radioactive uranium (U) on virgin and aged (modified with -OH or -COOH groups) polystyrene (PS) MPs at pH ranging from 3.0 to 9.0. The kinetic data showed that the U adsorption capacities of virgin PS and PS-COOH MPs were in the order of pH 7.0 > pH 8.2 > pH 4.5 > pH 9.0 > pH 3.0, whereas U adsorption on PS-OH MPs displayed a trend of pH 8.2 > pH 9.0 > pH 7.0 > pH 4.5 > pH 3.0. These outcomes were confirmed by X-ray photoelectron spectroscopy and binding energy analysis. Compared to virgin PS MPs, the higher U adsorption on aged MPs might be attributed to electrostatic attraction between deprotonated -COOH and (UO2)(3)(OH)(5)(+) at pH 7.0 for the PS-COOH MPs and between -OH and (UO2)(4)(OH)(7)(+) or (UO2)(3)(OH)(7)(-) at pH 8.2 for the PS-OH MPs. Intermolecular interaction calculations demonstrated that hydrogen bonding interaction driven by electrostatic and polarization energies contributed to the improved U adsorption amount of the PS-COOH MPs at pH 7.0 and the PS-OH MPs at pH 8.2. Our understanding of the mechanisms by which pH regulates U adsorption by MPs is critical for evaluating the fate and hazard of co-existing radionuclides and MPs in aquatic environments.