Adjusting the Structure-Activity Relationship of MOFs to Obtain Electrocatalysts with Higher Hydrogen Evolution and Urea Oxidation Performance by Introducing Different Linkers.

Three kinds of metal-organic frameworks possessing analogous structures were prepared by regulating the structure units of organic linkers. MOF/nickel foam electrocatalysts were formed by in situ hydrothermal growth of MOFs on a clean supported substrate nickel foam (NF), and the corresponding composites were prepared. We phosphatated them and obtained the heterojunction catalyst. Different structure units in the ligand have significant influences on the phosphating, resulting in heterogeneous materials that are not quite the same. Among them, heterogeneous materials with Co2P and NiP have the best catalytic performance. We also studied the urea oxidation reaction (UOR) properties of the materials and proved that it is feasible to improve the UOR performance of MOF/NF composites by regulating the structure units in the organic linkers. The results provided an idea for the reasonable selection of organic ligands to construct MOFs to regulate the electrocatalytic performance.

Enhanced synergistic catalysis of bisphenol A in river water using an anti-aging photocatalytic membrane.

Bisphenol A (BPA), as an endocrine disruptor, poses a potential threat to ecosystems and human health in aquatic environments. Membrane catalytic systems can accelerate the degradation of BPA and facilitate its conversion into harmless compounds. Nevertheless, the complex nature of the water environments and the limited stability of catalysts often result in challenges such as catalyst aging and deactivation. Herein, an anti-aging multifunctional AgFeO2 catalytic material with electron transfer membrane support was prepared for synergistic catalysis of low-energy LED light (12 W) excitation and peroxydisulfate (PDS) activation. The anti-aging photocatalytic membrane completely degraded 10 ppm of BPA within 30 min, and did not show significant aging after the long-term synergistic catalytic process. In addition, actual river water was employed to assess the aging process and catalytic efficiency in a practical environment. A 60.79 cm2 photocatalytic membrane completely purified 10 L of BPA polluted river water, while the total organic carbon content decreased by 50 %. This was mainly due to the synergistic catalytic effect of the membrane, which boosted photoelectron transfer through electron transfer shortcuts, thereby enhancing persulfate activation. Overall, the multifunctional membrane provides an effective strategy for achieving a long-lasting catalytic effect and controlling photocatalyst aging in practice.

3D-printed controllable bio-accelerators with sustained release property to boost chromium (VI) inhibited denitrification recovery.

Although soluble bio-accelerators have proven effective in mitigating Cr(VI) inhibition within denitrification system, issues persist in immobilizing bio-accelerators and making them slow-release for sustained regulation. In this study, a novel strategy was proposed to fabricate immobilized bio-accelerators with controlled structure, sustained release property by 3D printing technology. Notably, the sustained release of bio-accelerators from 3D-printed bio-accelerators (3DP-B) lasted for at least 144 h. Compared to control group, 3DP-B with basic components (3DP-BB) shortened the recovery time by 1.4 folds, and the COD and NO3--N removal efficiency was 36.5 % and 38.0 % higher than that of natural recovery. Correspondingly, the activity of key enzymes (nitrate reductase, nitrite reductase, nitric oxide reductase, and nitrous oxide reductase), electron transfer system activity and extracellular polymer substances of denitrification biofilm maintained at relatively high levels. Furthermore, introducing 60 mg·L-1 anthraquinone-2,6-disulfonate (AQDS) into the ink showed noticeable superiority on the bio-inhibition release over 1000 mg·L-1 AQDS. The released AQDS facilitated the electron transport capacity by 1.25 times compared with control group. The groundbreaking findings of this study could advance the development of 3D printing technology and utilization of bio-accelerators in the field of wastewater treatment.

Apoptosis and its role in postmortem meat tenderness: A comprehensive review.

Tenderness is considered a crucial attribute of postmortem meat quality, directly influencing consumers' preferences and industrial economic benefits. The degradation of myofibrillar proteins by endogenous enzymes within muscle fibers is believed to be the most effective pathway for meat tenderization. After animals are slaughtered and exsanguinated, there is a significant accumulation of reactive oxygen species (ROS), and a dramatic depletion of adenosine triphosphate (ATP) in muscle, leading to inevitable cell death. Caspases are activated in postmortem muscle cells, which disrupt the cell structure and improve meat tenderness through protein hydrolysis. In this review, we systematically summarized the three primary types of cell death studied in postmortem muscle: apoptosis, autophagy and necrosis. Furthermore, we emphasized the molecular mechanisms of apoptosis and its corresponding apoptotic pathways (mitochondrial apoptosis, death receptors, and endoplasmic reticulum stress) that affect meat tenderness during muscle conversion to meat. Additionally, factors affecting apoptosis were comprehensively discussed, such as ROS, heat shock proteins, calcium (Ca2+)/calpains, and Bcl-2 family proteins. Finally, this comprehensive review of existing research reveals that apoptosis is mainly mediated by the mitochondrial pathway. This ultimately leads to myofibrillar proteins degradation through caspase activation, improving meat tenderness. This review summarizes the research progress on postmortem muscle apoptosis and its molecular mechanisms in meat tenderization. We hope this will enhance understanding of postmortem meat tenderness and provide a theoretical basis for meat tenderization techniques development in the future.

Interaction of poly dimethyl diallyl ammonium chloride with sludge components: Anaerobic digestion performance and adaptive changes of anaerobic microbes.

The wide utilization of poly dimethyl diallyl ammonium chloride (polyDADMAC) in industrial conditions leads to its accumulation in waste activated sludge (WAS), thereby affecting subsequent WAS treatment processes. This work investigated the interaction between polyDADMAC and WAS components from the perspective of anaerobic digestion (AD) performance and anaerobes adaptability variation. The results showed that polyDADMAC decreased the content of biodegradable organic substrates (i.e., soluble protein and carbohydrate) by binding with the functional groups and then settling to the solid phase, thus impeding the subsequent utilization. Higher concentrations of polyDADMAC prompted an initial protective response of excreting organic substrates into extracellular environment, but its toxicity to archaea was irreversible. Consequently, polyDADMAC inhibited the processes of AD and induced a 30 % reduction in methane production with 0.05 g polyDADMAC/g total suspended solid (TSS) addition. Changes in microbial community structure indicated that archaea involved in methane production (e.g., Anaerolineaceae sp. and Methanosaeta sp.) were inhibited when exposed to polyDADMAC. However, several adaptive bacteria with the ability of utilizing complex organics and participating in nitrogen cycle (e.g., Aminicenantales sp. and Ellin6067 sp.) were enriched with the above dosage. Specifically, the decreased abundance of genes relevant to methane metabolism pathway (i.e., mer and cdh) and increased abundance of genes involved in metabolism of cofactors and vitamins (e.g., nad and thi) indicated the toxicity of polyDADMAC and the irritant response of microflora. Moreover, polyDADMAC underwent degradation in AD system, resulting in a 12 % reduction in 15 days, accompanied by an increase in the -NO2 functional group. In general, this study provided a thorough understanding of the interaction between polyDADMAC and WAS components, raising concerns regarding the elimination of endogenous pollutants during AD.

Interspecific competition enhances microcystin production by Microcystis aeruginosa under the interactive influences of temperature and nutrients.

Global warming and eutrophication contribute to frequent occurrences of toxic algal blooms in freshwater systems globally, while there is a limited understanding of their combined impacts on toxin-producing algal species under interspecific competitions. This study investigated the influences of elevated temperatures, lights, nutrient enrichments and interspecific interactions on growth and microcystin (MC) productions of Microcystis aeruginosa in laboratory condition. Our results indicated that elevated temperatures and higher nutrient levels significantly boosted biomass and specific growth rates of Microcystis aeruginosa, which maintained a competitive edge over Chlorella sp. Specifically, with phosphorus levels between 0.10 and 0.70 mg P L-1, the growth rate of Microcystis aeruginosa in mixed cultures increased by 23 %-52 % compared to mono-cultures, while the growth rate of Chlorella sp. shifted from positive in mono-cultures to negative in mixed cultures. Redundancy and variance partition analyses suggested that Chlorella sp. stimulate MC production in Microcystis aeruginosa and nutrient levels outshine temperature for toxin productions during competition. Lotka‒Volterra model revealed a positive correlation between the intensities of competitions and MC concentration. Our findings indicate that future algal bloom mitigation strategies should consider combined influence of temperature, nutrients, and interspecific competition due to their synergistic effects on MC productions.

3D printing for constructing biocarriers using sodium alginate/ε-poly-l-lysine ink: Enhancing microbial enrichment for efficient nitrogen removal in wastewater.

The microbial enrichment of traditional biocarriers is limited due to the inadequate consideration of spatial structure and surface charging characteristics. Here, capitalizing on the ability of 3D printing technology to fabricate high-resolution materials, we further designed a positively charged sodium alginate/ε-poly-l-lysine (SA/ε-PL) printing ink, and the 3D printed biocarriers with ideal pore structure and rich positive charge were constructed to enhance the microbial enrichment. The rheological and mechanical tests confirmed that the developed SA/ε-PL ink could simultaneously satisfy the smooth extrusion for printing process and the maintenance of 3D structure. The utilization of the ε-PL secondary cross-linking strategy reinforced the 3D mechanical structure and imparted the requisite physical properties for its application as a biocarrier. Compared with traditional sponge carriers, 3D printed biocarrier had a faster initial attachment rate and a higher biomass of 14.58 ± 1.18 VS/cm3, and the nitrogen removal efficiency increased by 53.9 %. Besides, due to the superior electrochemical properties and biocompatibility, the 3D printed biocarriers effectively enriched the electroactive denitrifying bacteria genus Trichococcus, thus supporting its excellent denitrification performance. This study provided novel insights into the development of new functional biocarriers in the wastewater treatment, thereby providing scientific guidance for practical engineering.

Harnessing Risk Assessment for Thrombosis and Bleeding to Optimize Anticoagulation Strategy in Nonvalvular Atrial Fibrillation.

BACKGROUND: Oral anticoagulation (OAC) following catheter ablation (CA) of nonvalvular atrial fibrillation (NVAF) is essential for the prevention of thrombosis events. Inappropriate application of OACs does not benefit stroke prevention but may be associated with a higher risk of bleeding. Therefore, this study aims to develop clinical data-driven machine learning (ML) methods to predict the risk of thrombosis and bleeding to establish more precise anticoagulation strategies for patients with NVAF. METHODS: Patients with NVAF who underwent CA therapy were enrolled from Southwest Hospital from 2015 to 2023. This study compared eight ML algorithms to evaluate the predictive power for both thrombosis and bleeding. Model interpretations were recognized by feature importance and SHapley Additive exPlanations methods. With potential essential risk factors, simplified ML models were proposed to improve the feasibility of the tool. RESULTS: A total of 1,055 participants were recruited, including 105 patients with thrombosis and 252 patients with bleeding. The models based on XGBoost achieved the best performance with accuracies of 0.740 and 0.781 for thrombosis and bleeding, respectively. Age, BNP, and the duration of heparin are closely related to the high risk of thrombosis, whereas the anticoagulation strategy, BNP, and lipids play a crucial role in the occurrence of bleeding. The optimized models enrolling crucial risk factors, RF-T for thrombosis and Xw-B for bleeding, achieved the best recalls of 0.774 and 0.780, respectively. CONCLUSION: The optimized models will have a great application potential in predicting thrombosis and bleeding among patients with NVAF and will form the basis for future score scales.

New insights into N2O emission and electron competition under different chemical oxygen demand to nitrogen ratios in a biofilm system.

Nitrous oxide (N2O) is a greenhouse gas that could accumulate during the heterotrophic denitrification process. In this study, the effects of different chemical oxygen demand to nitrogen ratio (COD/N) on N2O production and electron competition was investigated. The electron competition was intensified with the decrease of electron supply, and Nos had the best electron competition ability. The model simulation results indicated that the degradation of NOx-Ns was a combination of diffusion and biological degradation. As reaction proceeding, N2O could accumulate inside biofilm. A thinner biofilm and a longer hydraulic retention time (HRT) might be an effective way to control N2O emission. The application of mathematical model is an opportunity to gain deep understanding of substrate degradation and electron competition inside biofilm.

Discordant High Remnant Cholesterol With LDL-C Increases the Risk of Stroke: A Chinese Prospective Cohort Study.

BACKGROUND: Previous studies focusing on assessing the effects of remnant cholesterol (RC) and low-density lipoprotein cholesterol (LDL-C) on stroke may not consider their mutual influence. We aimed to explore the associations of RC and discordant high RC with LDL-C with stroke, ischemic stroke (IS), and hemorrhagic stroke. METHODS: This prospective cohort study was conducted based on 3 cohorts of the China-PAR (Prediction for Atherosclerotic Cardiovascular Disease Risk in China) project. RC was calculated as non-high-density lipoprotein cholesterol minus LDL-C estimated by Martin/Hopkins equations. Concordant/discordant categories for RC versus LDL-C were determined based on cut-points of 130 mg/dL for LDL-C and equivalent percentile (32.50 mg/dL) for RC. Cox models were used to estimate adjusted hazard ratios and 95% CIs for incident stroke. RESULTS: Among 113 448 participants recruited at baseline, a total of 98 967 participants were eligible for the final analysis (mean age of 51.44 years; 40.45% were men). During 728 776.87 person-years of follow-up, 2859 stroke cases, 1811 IS cases, and 849 hemorrhagic stroke cases were observed. RC was positively associated with stroke and IS, but not hemorrhagic stroke, with adjusted hazard ratios (95% CIs) of 1.06 (1.02-1.10), 1.09 (1.04-1.13), and 0.95 (0.88-1.03) for per SD increase in RC. Compared with low LDL-C/low RC group, low LDL-C/high RC group had higher risks of stroke (adjusted hazard ratio, 1.15 [95% CI, 1.02-1.30]) and IS (1.19, 1.03-1.38), while high LDL-C/low RC group had no increased risk of stroke (1.07 [0.95-1.20]) and IS (1.09 [0.94-1.25]). CONCLUSIONS: Higher RC was associated with increased risks of stroke and IS but not hemorrhagic stroke. Discordantly high RC, not discordantly high LDL-C, conferred higher risks of stroke and IS. Our findings support further lowering RC by interventions to reduce residual IS risk.

Discovery, identification and mechanism of chemosensitivity-relate biomarker inter-α-trypsin inhibitor heavy chain 4 in metastatic colorectal cancer.

Predictive biomarkers of response to chemotherapy in patients with metastatic colorectal cancer (mCRC) are needed to better characterize tumors and enable more tailored therapies. Here we used serum proteomics to screen for chemotherapy predictive markers. We found that higher baseline serum inter-α-trypsin inhibitor Heavy Chain 4 (ITIH4) expression in newly diagnosed mCRC patients was associated with poorer response to standard first-line chemotherapy. In addition, the higher expression of ITIH4 in CRC tissue also suggested poorer prognosis mCRC patients. Moreover, the overexpression of ITIH4 could promote the proliferation of CRC cells and reduce the sensitivity of CRC cells to 5-fluorouracil (5-FU) by inhibiting apoptosis in vivo and vitro. Through RNA-seq combined with bioinformatics analysis, we speculated that ITIH4 may activate phosphatidyl 3-kinase-protein kinase B (PI3K-AKT) pathway to inhibit apoptosis, thereby reducing the sensitivity of CRC cells to 5-FU. In conclusion, our findings unveil that ITIH4 is associated with CRC resistance to 5-FU, and may serve as a potential predictive biomarker for the sensitivity of advanced CRC patients to standard first-line chemotherapy regimens, and also provide a potential therapeutic target to render 5-FU resistance in CRC patients.

Sulforaphane Ameliorate Cadmium-Induced Blood-Thymus Barrier Disruption by Targeting the PI3K/AKT/FOXO1 Axis.

Cadmium (Cd) is a transition metal ion that is extremely harmful to human and animal biological systems. Cd is a toxic substance that can accumulate in the food chain and cause various health issues. Sulforaphane (SFN) is a natural bioactive compound with potent antioxidant properties. In our study, 80 1 day-old chicks were fed with Cd (140 mg/kg BW/day) and/or SFN (50 mg/kg BW/day) for 90 days. The blood-thymus barrier (BTB) is a selective barrier separating T-lymphocytes from blood and cortical capillaries in the thymus cortex. Our research revealed that Cd could destroy the BTB by downregulating Wnt/ß-catenin signaling and induce immunodeficiency, leading to irreversible injury to the immune system. The study emphasizes the health benefits of SFN in the thymus. SFN could ameliorate Cd-triggered BTB dysfunction and pyroptosis in the thymus tissues. SFN modulated the PI3K/AKT/FOXO1 axis, improving the level of claudin-5 (CLDN5) in the thymus to alleviate BTB breakdown. Our findings indicated the toxic impact of Cd on thymus, and BTB could be the specific target of Cd toxicity. The finding also provides evidence for the role of SFN in maintaining thymic homeostasis for Cd-related health issues.

Inhibitory mechanism of Cr(VI) on sulfur-based denitrification: Bio-toxicity, bio-electron characteristics, and microbial evolution.

Sulfur-based denitrification is a promising technology for efficient nitrogen removal in low-carbon wastewater, while it is easily affected by toxic substances. This study revealed the inhibitory mechanism of Cr(VI) on thiosulfate-based denitrification, including bio-toxicity and bio-electron characteristics response. The activity of nitrite reductase (NIR) was more sensitive to Cr(VI) than that of nitrate reductase (NAR), and NIR was inhibited by 21.32 % and 19.86 % under 5 and 10 mg/L Cr(VI), resulting in 10.12 and 15.62 mg/L of NO2--N accumulation. The biofilm intercepted 36.57 % of chromium extracellularly by increasing 25.78 % of extracellular polymeric substances, thereby protecting microbes from bio-toxicity under 5 mg/L Cr(VI). However, it was unable to resist 20-30 mg/L of Cr(VI) bio-toxicity as 19.95 and 14.29 mg Cr/(g volatile suspended solids) invaded intracellularly, inducing the accumulation of reactive oxygen species by 165.98 % and 169.12 %, which triggered microbial oxidative-stress and damaged the cells. In terms of electron transfer, S2O32- oxidation was inhibited, and parts of electrons were redirected intracellularly to maintain microbial activity, resulting in insufficient electron donors. Meanwhile, the contents of flavin adenine dinucleotide and cytochrome c decreased under 5-30 mg/L Cr(VI), reducing the electron acquisition rate of denitrification. Thermomonas (the dominant genus) possessed denitrification and Cr(VI) resistance abilities, playing an important role in antioxidant stress and biofilm formation. ENVIRONMENTAL IMPLICATION: Sulfur-based denitrification (SBD) is a promising method for nitrate removal in low-carbon wastewater, while toxic heavy metals such as Cr(VI) negatively impair denitrification. This study elucidated Cr(VI) inhibitory mechanisms on SBD, including bio-toxicity response, bio-electron characteristics, and microbial community structure. Higher concentrations Cr(VI) led to intracellular invasion and oxidative stress, evidenced by ROS accumulation. Moreover, Cr(VI) disrupted electron flow by inhibiting thiosulfate oxidation and affecting electron acquisition by denitrifying enzymes. This study provided valuable insights into Cr(VI) toxicity, which is of great significance for improving wastewater treatment technologies and maintaining efficient and stable operation of SBD in the face of complex environmental challenges.

Bio-promoter mediated denitrification recovery from Cd(II) stress: Microbial activity resilience, electron behavior enhancement and microbial community evolution.

Denitrification is fragile to toxic substances, while currently there are few regulation strategies for toxic substance-stressed denitrification. This study proposed a combined bio-promoter composed of basic bio-promoter (cytokinin, biotin, L-cysteine, and flavin adenine dinucleotide) and phosphomolybdic acid (PMo12) to recover cadmium(II) (Cd(II)) stressed denitrification. By inhibiting 58.02% and 48.84% of nitrate reductase and nitrite reductase activities, Cd(II) caused all the influent nitrogen to accumulate as NO3--N and NO2--N. Combined bio-promoter shortened the recovery time by 21 cycles and improved nitrogen removal efficiency by 10% as the synergistic effect of basic bio-promoter and PMo12. Basic bio-promoter enhanced antioxidant enzyme activities for reactive oxygen species clearance and recovered 23.30% of nicotinamide adenine dinucleotide for sufficient electron donors. Meanwhile, PMo12 recovered electron carriers contents, increasing the electron transfer activity by 60.81% compared with self-recovery. Bio-promoters enhanced the abundance of denitrifiers Seminibacterium and Dechloromonas, which was positively correlated with rapid recovery of denitrification performance.

Graphite-N reinforced sludge biochar electrode: A experimental and DFT theoretical analysis of efficient evolution and in-situ utilization of H2O2.

Rational reuse of municipal sludge to produce electro-Fenton electrode can not only save resources, but also produce superior peroxide and degradation pollutants simultaneously. Herein, a novel electro-Fenton electrode derived from sludge biochar loaded on Ni foam (SBC@Ni) was constructed via high temperature pyrolysis and chemical coating for efficient H2O2 evolution and pollutant degradation. Systematic experiments and density functional theory calculations (DFT calculation) explained that the production of graphite C and graphite N during high-temperature pyrolysis of municipal sludge can greatly enhance the oxygen reduction reaction of SBC@Ni electrode and promote the evolution of H2O2. And the hybrid heterojunctions, such as FeP, also played a key role in electrocatalytic processes. Notably, the electrode still exhibited excellent performance after 1000 linear scans and 12 h of continuous current stimulation, which demonstrated the excellent stability of the electrode. Moreover, SBC@Ni electrode can not only effectively oxidize 4-chlorophenol through the electro-Fenton effect, but also fully mineralize organic matter, indicating promising environmental application. The free radical quenching experiment also revealed that the ·OH is the main active species for 4-CP degradation in SBC@Ni electro-Fenton system.

Interpretation of Frequency Effect for High-Strength Steels with Three Different Strength Levels via Crystal Plasticity Finite Element Method.

The fatigue behavior of a high-strength bearing steel tempered under three different temperatures was investigated with ultrasonic frequency and conventional frequency loading. Three kinds of specimens with various yield strengths exhibited obvious higher fatigue strengths under ultrasonic frequency loading. Then, a 2D crystal plasticity finite element method was adopted to simulate the local stress distribution under different applied loads and loading frequencies. Simulations showed that the maximum residual local stress was much smaller under ultrasonic frequency loading in contrast to that under conventional frequency at the same applied load. It was also revealed that the maximum local stress increases with the applied load under both loading frequencies. The accumulated plastic strain was adopted as a fatigue indicator parameter to characterize the frequency effect, which was several orders smaller than that obtained under conventional loading frequencies when the applied load was fixed. The increment of accumulated plastic strain and the load stress amplitude exhibited a linear relationship in the double logarithmic coordinate system, and an improved fatigue life prediction model was established.

Efficient electrosynthesis of HO2- from air for sulfide control in sewers.

Electrochemically in-situ generation of oxygen and caustic soda is promising for sulfide management while suffers from scaling, poor inactivating capacity, hydrogen release and ammonia escape. In this study, the four-compartment electrochemical cell efficiently captured oxygen molecules from the air chamber to produce HO2- without generating toxic by-products. Meanwhile, the catalyst layer surface of PTFE/CB-GDE maintained a relatively balanced gas-liquid micro-environment, enabling the formation of enduring solid-liquid-gas interfaces for efficient HO2- electrosynthesis. A dramatic increase in HO2- generation rate from 453.3 mg L-1 h-1 to 575.4 mg L-1 h-1 was attained by advancement in operation parameters design (flow channels, electrolyte types, flow rates and circulation types). Stability testing resulted in the HO2- generation rate over 15 g L-1 and the current efficiency (CE) exceeding 85%, indicating a robust stable operational capacity. Furthermore, after 120 mg L-1 HO2- treatment, an increase of 11.1% in necrotic and apoptotic cells in the sewer biofilm was observed, higher than that achieved with the addition of NaOH, H2O2 method. The in-situ electrosynthesis strategy for HO2- represents a significance toward the practical implementation of sulfide abatement in sewers, holding the potential to treat various sulfide-containing wastewater.

How halogenated aromatic compounds affect the electron supply and consumption in glucose supported denitrification?

Halogenated aromatic compounds possess bidirectional effects on denitrifying bio-electron behavior, providing electrons and potentially interfering with electron consumption. This study selected the typical 4-chlorophenol (4-CP, 0-100 mg/L) to explore its impact mechanism on glucose-supported denitrification. When COD(glucose)/COD(4-CP)=28.70-3.59, glucose metabolism remained the dominant electron supply process, although its removal efficiency decreased to 73.84-49.66 %. When COD(glucose)/COD(4-CP)=2.39-1.43, 4-CP changed microbial carbon metabolism priority by inhibiting the abundance of glucose metabolizing enzymes, gradually replacing glucose as the dominant electron donor. Moreover, 5-100 mg/L 4-CP reduced adenosine triphosphate (ATP) by 15.52-24.67 % and increased reactive oxygen species (ROS) by 31.13-63.47 %, causing severe lipid peroxidation, thus inhibiting the utilization efficiency of glucose. Activated by glucose, 4-CP dechlorination had stronger electron consumption ability than NO2--N reduction (NO3--N > 4-CP > NO2--N), combined with the decreased nirS and nirK genes abundance, resulting in NO2--N accumulation. Compared with the blank group (0 mg/L 4-CP), 5-40 mg/L and 60-100 mg/L 4-CP reduced the secretion of cytochrome c and flavin adenine dinucleotides (FAD), respectively, further decreasing the electron transfer activity of denitrification system. Micropruina, a genus that participated in denitrification based on glucose, was gradually replaced by Candidatus_Microthrix, a genus that possessed 4-CP degradation and denitrification functions after introducing 60-100 mg/L 4-CP.

Enhancement of bio-promoters on hexavalent chromium inhibited sulfur-driven denitrification: repairing damage, accelerating electron transfer, and reshaping microbial collaboration.

Proposing recovery strategies to recover heavy-metal-inhibited sulfur-driven denitrification, as well as disclosing recovery mechanisms, can provide technical support for the stable operation of bio-systems. This study proposed an effective bio-promoter (mediator-promoter composed of L-cysteine, biotin, cytokinin, and anthraquinone-2,6-disulfonate) to recover Cr(VI) inhibited sulfur-driven denitrification, which effectively reduced the recovery time of NO3--N reduction (18-21 cycles) and NO2--N reduction (27-42 cycles) compared with self-recovery. The mediator-promoter repaired microbial damage by promoting intracellular chromium efflux. Moreover, the mediator-promoter reduced the accumulated reactive oxygen species by stimulating the secretion of antioxidant enzymes, reaching equilibrium in the oxidative-antioxidant system. To improve electron transmission, the mediator-promoter restored S2O32- oxidation to provide adequate electron donors and increased electron transfer rate by increasing cytochrome c levels. Mediator-promoter boosted the abundance of Thiobacillus (sulfur-oxidizing bacterium) and Simplicispira (denitrifying bacterium), which were positively correlated, facilitating the rapid denitrification recovery and the long-term stable operation of recovered systems.