Bioresource Technology最新文献

Biomineralization influences the structural stability, biomass retention, and mass transfer of anaerobic ammonium oxidation (anammox) granules, yet size-associated mineral differences under low-phosphate conditions remain insufficiently resolved. Mature granules from a long-term upflow anaerobic sludge blanket reactor operated at 2.7 mg P L^-1 were separated into five size fractions (<0.6, 0.6-1.18, 1.18-2.36, 2.36-4.0, and >4.0 mm) and characterized using integrated mineralogical, spectroscopic, and microbial analyses. Ash contents ranged from 65.29 to 74.43%, while specific anammox activity increased with granule size. Short-term assays showed apparent decreases in dissolved Ca²⁺ and phosphate, with net Ca/P removal ratios above 4, indicating that stoichiometric hydroxyapatite (HAP) precipitation alone could not account for the observed aqueous changes. Calcite-rich particles were recovered from fine or peripheral material, whereas internally recovered particles contained HAP with features consistent with carbonate substitution. Tightly bound extracellular polymeric substances (EPS) were more abundant and protein-rich than loosely bound EPS and exhibited greater Ca²⁺-binding capacity. Larger granules showed higher relative abundances of several heterotrophic taxa, while the dominant anammox genus remained comparatively stable, suggesting size-associated differentiation of microbial partners potentially involved in organics and nitrogen turnover. These findings connect size-associated mineral differences with EPS binding properties, microbial community composition, and anammox activity, informing the evaluation of granule management under low-phosphate conditions.

Composite polluted wastewater (CPW) containing ammonium nitrogen (NH₄⁺-N) and Cu²⁺ discharged from industrial and agricultural activities poses severe threats to ecological environments and human health. Although nitrification and biomineralization technologies have been separately applied to the removal of NH₄⁺-N and Cu²⁺, nitrate accumulation was a potential drawback of the former, while high toxicity of Cu²⁺ may triggered bacterial denaturation in the latter treatment system. In the present study, Bacillus megaterium was used to simultaneously remove NH₄⁺-N and Cu²⁺ from CPW via heterotrophic nitrification-aerobic denitrification (HNAD) and microbially-induced phosphate precipitation (MIPP). Kinetic analyses revealed that the optimal cultivation conditions for Bacillus megaterium included an initial NH₄⁺ concentration of 100 mg/L, an initial Cu²⁺ concentration of 100 mg/L, and an initial pH of 7, with corresponding removal efficiencies of 99.7% for both NH₄⁺ and Cu²⁺. Microscopic characterizations demonstrated that the bacteria converted NH₄⁺ into N₂ through the HNAD process and simultaneously generated alkalinity required for the MIPP process, thereby removing Cu²⁺ via adsorption and coprecipitation. Furthermore, the removal of NH₄⁺ inhibited the formation of copper-ammonia complexes. This work provides a novel insight into the practical application of integrated HNAD and MIPP technologies for the simultaneous remediation of CPW co-contaminated with NH₄⁺-N and Cu²⁺.

Bio-production of the high-value health-promoting metabiotic indole-3-lactate (3-ILA) by lactic acid bacteria (LAB) and bifidobacteria remains constrained to micromolar levels. This limitation is largely due to pyruvate outcompeting indole-3-pyruvate (3-IPYA) for LDH and NADH, leading to lactate accumulation and suppressed 3-ILA synthesis. In this study, previously developed high-glucose-adaptive Lactiplantibacillus plantarum strains LP-D-4G and LP-D-10E were evaluated as chassis for enhanced 3-ILA production. Compared with the parental strain, the adaptive strains exhibited increased l-tryptophan (l-Trp) utilization and 3-ILA production during resting-cell bioconversion, together with altered pyruvate-derived product distributions and intracellular NAD(H) profiles. Systematic genome mining and heterologous expression in Escherichia coli identified five active lactate dehydrogenases (LDH2/3/5/6/7) and one aromatic-amino-acid aminotransferase (ArAT2). Co-expression of LDH7 and ArAT2 in strain LP-D-4G achieved 6.06 mM 3-ILA, 0.95 mol/mol l-Trp conversion, and a 3-ILA/(3-ILA + lactate) ratio of 0.31 mol/mol in whole-cell bioconversion. Furthermore, optimization of l-Trp and glucose feeding strategies improved 3-ILA production. In a scaled-up 150-mL fed-batch system, strain LP-D-4G overexpressing LDH7 and ArAT2 produced 20.09 mM 3-ILA at 96 h, representing the highest titer reported to date for LAB-based 3-ILA production. At peak, 3-ILA yield, productivity, and the 3-ILA/(3-ILA + lactate) ratio reached 0.84 mol/mol l-Trp, 69.45 mg/L/h, and 0.25 mol/mol, respectively. This study establishes a food-grade platform for bioactive 3-ILA production and demonstrates an effective strategy to reduce lactate and enhance 3-ILA by combining a high-glucose-adaptive chassis with pathway reinforcement.

Developing non-precious cathode catalysts for neutral oxygen reduction is critical to improving microbial fuel cell performance. Here, NH₄Cl-assisted secondary pyrolysis was used to reconstruct ZIF-67-derived Co/N-doped carbon and regulate Co/N surface environments. The optimized CoNC-1 combined an open porous framework, abundant defects, improved wettability, and favorable pyridinic N/Co-N_x-containing surface configurations. Density functional theory indicated adsorbate-induced Co 3d redistribution and a theoretical overpotential of 0.244 V for the four-electron oxygen reduction pathway at the Co-N-C model site. In PBS condition, CoNC-1 delivered a half-wave potential of 0.592 V vs. RHE, a limiting current density of 6.37 mA·cm^-2, an H₂O₂ yield of 5.18%, and an electron-transfer number of approximately 3.90. As an air-cathode catalyst, CoNC-1 achieved a maximum power density of 681.5 ± 5.99 mW m^-2, 87.2% COD removal, and 15.3% coulombic efficiency. These results demonstrate that coupling framework reconstruction with surface Co/N regulation improves neutral ORR and wastewater-to-electricity conversion.

Anaerobic digestion (AD) is a promising method for treating organic waste, but it requires thorough management. While it is known that organic loading fluctuations affect anaerobic digestion, their specific impact has not been verified. Therefore, this study hypothesized that the response to overload differs depending on the organic loading rate (OLR) strategy to which anaerobic digesters are adapted. To test this hypothesis, sequencing batch reactors were operated using whey as the substrate. Five operational conditions were compared under three fixed OLRs of 0.25, 1.0, and 2.0 g COD/L∙day (i.e., low-L, medium-M, and high-H, respectively) and two dynamic OLR regimes of stepwise oscillation (SO; M-L-M-H conditions) and drastic oscillation (DO; L-H conditions). After the initial operation period, all reactors were subjected to the same overload, recovery, and treatment (C-control, B-bioaugmentation). The LB and SOB reactors showed marked pH decreases and caproic acid accumulation, whereas the HB and DOB reactors showed delayed propanoic acid degradation. In contrast, the MB reactor exhibited superior performance in terms of volatile fatty acid (VFA) removal and pH recovery on D159. The microbial community changed dynamically according to the OLR history. PICRUSt2 analysis suggested that syntrophic VFA degradation and amino acid metabolism were affected by the OLR histories. Network analysis revealed putative associations between minor syntrophic acetate-oxidizing bacteria and Methanosarcina during recovery. Additionally, the connection of protein-related consortia (Aminobacterium-Methanomassiliicoccus) was inferred by network analysis. Overall, the results of this study indicate that prior OLR history shapes overload resilience by altering VFA degradation trajectories and microbial recovery patterns.

The reducing capacity (RC) and microbially mediated electron-transfer capacity (ETC) of compost-derived fulvic acid (FA) are closely related to its molecular structure and may influence Fe biogeochemical cycling. However, how these redox functions evolve with FA structure during composting remains poorly understood. Using Fe(III) as a prevalent environmental electron acceptor, this study innovatively quantified the reducing capacity(RC) and microbially mediated electron-transfer capacity(ETC) of FA throughout a full-scale municipal solid waste (MSW) composting process and linked these functions to structural evolution characterized by multidimensional spectroscopy. Compost-derived FA exhibited Fe(III)-form- and electron-transfer-role-dependent redox behavior. Its inorganic reducing capacity decreased significantly during composting, whereas its organic reducing capacity remained relatively stable and was consistently higher (mean IRC: 1.89 mmol e^- g^-1C, mean ORC: 3.21 mmol e^- g^-1C). In contrast, ETCs mediated by Shewanella oneidensis MR-1 and SP200 showed no significant temporal trends, with FA facilitating electron transfer more effectively to inorganic than to organically complexed Fe(III) in both bacterial systems. Multidimensional spectroscopic analyses revealed that variations in RC and ETC were associated with the evolution of fluorescent components, functional groups, and hydrogen-containing structures, while the structural correlates of ETC differed between MR-1 and SP200. These findings establish a structure-redox linkage for compost-derived FA under full-scale composting conditions and provide a functional perspective beyond conventional compositional characterization, supporting the evaluation of its potential roles in Fe cycling and other environmentally relevant redox processes.