Soluble Products Research Articles

Critical minority fractions causing membrane fouling in reclaimed water: Fouling characteristics, mechanisms and control strategies

In regard to membrane-based technologies of wastewater reclamation, the reported key foulants were faced with dilemma that they could not be effectively separated and extracted from reclaimed water for thorough investigation. In this study, the crucial foulants were proposed as “critical minority fraction (FCM)”, representing the fraction with molecular weight (MW) > 100 kDa which could be easily separated by physical filtration using MW cut-off membrane of 100 kDa with fairly high recovery ratio. FCM with low dissolved organic carbon (DOC) concentration (∼1 mg/L) accounted for less than 20% of the total DOC in reclaimed water, while contributed to more than 90% of the membrane fouling, and thus FCM could be considered as a “perfect criminal” causing membrane fouling. Furthermore, pivotal fouling mechanism was attributed to the significant attractive force between FCM and membranes, which led to severe fouling development due to the aggregation of FCM on membrane surface. Fluorescent chromophores of FCM were concentrated in regions of proteins and soluble microbial products, with proteins and polysaccharides accounted for 45.2% and 25.1% of the total DOC, specifically. FCM was further fractionated into six fractions, among which hydrophobic acids and hydrophobic neutrals were the dominant components in terms of DOC content (∼80%) as well as fouling contribution. Regarding to these pronounced properties of FCM, targeted fouling control strategies including ozonation and coagulation were applied and proved to achieve remarkable fouling control effect. High-performance size-exclusion chromatography results suggested that ozonation achieved distinct transformation of FCM into low MW fractions, while coagulation removed FCM directly, thus leading to effective fouling alleviation. Therefore, the investigation of the critical foulants was expected to help glean valuable insight into the fouling mechanism and develop targeted fouling control technologies in practical applications.

Application of Encapsulated Quorum Quenching Strain Acinetobacter pittii HITSZ001 to a Membrane Bioreactor for Biofouling Control

Quorum quenching (QQ) is a novel anti-biofouling strategy for membrane bioreactors (MBRs) used in wastewater treatment. However, actual operation of QQ-MBR systems for wastewater treatment needs to be systematically studied to evaluate the comprehensive effects of QQ on wastewater treatment engineering applications. In this study, a novel QQ strain, Acinetobacter pittii HITSZ001, was encapsulated and applied to a MBR system to evaluate the effects of this organism on real wastewater treatment. To verify the effectiveness of immobilized QQ beads in the MBR system, we examined the MBR effluent quality and sludge characteristics. We also measured the extracellular polymeric substances (EPS) and soluble microbial products (SMP) in the system to determine the effects of the organism on membrane biofouling inhibition. Additionally, changes in microbial communities in the system were analyzed by high-throughput sequencing. The results indicated that Acinetobacter pittii HITSZ001 is a promising strain for biofouling reduction in MBRs treating real wastewater, and that immobilization does not affect the biofouling control potential of QQ bacteria.

New recommendation for the thermal conductivity of irradiated (U, Pu)O2 fuels under fast reactor conditions. Comparison with recent experimental data

New experimental results obtained at the Joint Research Centre in Karlsruhe (JRC-Karlsruhe) within the European Sustainable Nuclear Industrial Initiative Plus project (ESNII+) were used to develop an updated recommendation for the thermal conductivity of (U, Pu)O2 fuels irradiated in fast reactor (FR) conditions. Fresh and irradiated FR fuels were characterised, and their thermal diffusivity and heat capacity were measured by the laser flash technique. The thermal conductivity of those fuels was calculated, using hydrostatic density measurements when available or using calculated density.The thermal conductivity model, developed in this work, describes different effects induced by irradiation on the degradation of thermal conductivity: soluble fission products (FPs), precipitated FPs, radiation damage, and porosity. Those effects are considered in separate corrective factors, which depend on the chemical composition of the irradiated fuel, its microstructure, and the temperature. To estimate these parameters, thermomechanical calculations (PLEIADES-GERMINAL V2) and thermochemical calculations (Thermo-Calc V4.1 with the TAF-ID V11 database) were carried out in conjunction. The data provided for each fuel sample consisted of fuel temperature, burn-up, end-of-life (EOL) isotopic composition, molar fraction of the dissolved FPs in the matrix, molar fraction of the oxide, and the metallic precipitated phases, density, produced and released fission gases.In this work, we showed a clear discrepancy between the experimental data and the most widely used thermal conductivity model for irradiated fuels (Lucuta et al., 1996). Lucuta's model was then modified and a new recommendation for FR (U, Pu)O2 fuels was provided. This work demonstrates that by introducing the neodymium content as the parameter driving the thermal conductivity of the matrix, a better agreement between the model and the experimental data can be achieved. This paper discusses the uncertainties related to the irradiation conditions and the data provided by the GERMINAL-Thermo-Calc calculation.

Simulation of Co-60 uptake on stainless steel and alloy 690 using the OSCAR v1.4 code integrating an advanced dissolution-precipitation model

The contamination of a nuclear cooling system by activated corrosion products (ACPs) is a process that involves many different mechanisms all interacting with each other. One of the most important mechanisms is dissolution-precipitation. This governs the transfer of soluble corrosion products between the circulating water and the immobile oxidized surfaces, and is strongly dependent on the water chemistry. The dissolution-precipitation model was improved in version 1.4 of the OSCAR computer code, which simulates the ACPs transfer in nuclear reactor systems. The OSCAR v1.4 code is now able to better calculate the incorporation of minor species (e.g., a cobalt isotope) into oxides using the chemistry module, PHREEQCEA, which determines the composition of an ideal solid solution and the equilibrium concentrations of elements in the aqueous solution. This model was challenged by comparing the results obtained using OSCAR v1.4 with the experimental results of a test performed in a dedicated loop by Studsvik Nuclear AB. Finally, with this model, the OSCAR v1.4 code accurately reproduces soluble 60Co uptake on stainless steel and alloy 690 under various experimental conditions (pH, Zn injection and flow rate).

Biochar Addition in Membrane Bioreactor Enables Membrane Fouling Alleviation and Nitrogen Removal Improvement for Low C/N Municipal Wastewater Treatment

Membrane bioreactors (MBRs) are frequently used to treat municipal wastewater, but membrane fouling is still the main weakness of this technology. Additionally, the low carbon-nitrogen (C/N) ratio influent has been shown to not only increase the membrane fouling, but also introduce challenges to meet the effluent discharge standard for nitrogen removal. Herein, the authors addressed the challenges by adding cost-effective biochar. The results suggested that the biochar addition can enable membrane fouling alleviation and nitrogen removal improvement. The reduced membrane fouling can be ascribed to the biochar adsorption capacity, which facilitates to form bigger flocs with carbon skeleton in biochar as a core. As a result, the biochar addition significantly altered the mixed liquor suspension with soluble microbial product (SMP) concentration reduction of approximately 14%, lower SMP protein/polysaccharide ratio from 0.28 ± 0.02 to 0.22 ± 0.03, smaller SMP molecular weight and bigger sludge particle size from 67.68 ± 6.9 μm to 113.47 ± 4.8 μm. The nitrogen removal is also dramatically improved after biochar addition, which can be due to the initial carbon source release from biochar, and formation of aerobic-anaerobic microstructures. Microbial diversity analysis results suggested more accumulation of denitrification microbes including norank_f__JG30-KF-CM45 and Plasticicumulans. Less relative abundance of Aeromonas after biochar addition suggested less extracellular polymer substance (EPS) secretion and lower membrane fouling rate.

Effect of starch-coated magnetic particles on treatment performance and membrane fouling in membrane bioreactor for low carbon/nitrogen municipal wastewater treatment

Membrane bioreactor (MBR) is an attractive sewage treatment technology but the major weakness remains in membrane fouling. Nowadays, magnetic activated sludge process with magnetic particle addition has been extensively investigated for membrane fouling mitigation due to the excellent magnetic bio-effect. However, the bioeffect is still limited and further study to enhance the fouling control is needed. Herein, the starch-coated magnetic particles (MsP) were fabricated and utilized to alleviate membrane fouling and enhance the treatment performance for low carbon/nitrogen municipal wastewater treatment. The MsP addition in MBR can effectively mitigate the membrane fouling which might be due to the magnetic bio-effect and enhanced bioflocculation, leading to the lower soluble microbial product (SMP) concentration from 17.3 ± 1.7 to 13.1 ± 0.7 mg L−1, higher microbial dehydrogenase activity from 234.65 ± 11.21 to 430.57 ± 39.48 mgTF gVSS−1h−1, bigger sludge particle size and more extracted extracellular polymer substances (EPS) secretion in the bulk sludge. Additionally, MsP particle can facilitate to form an aerobic and anoxic microenvironment, which is conducive to improve the nitrogen removal for low carbon/nitrogen municipal wastewater treatment. Microbial diversity analyses revealed that MsP addition enriched Flavobacterium sp, leading to more EPS secretion and therefore enhance the hydrophobic property and aggregation ability of sludge flocs to mitigate membrane fouling. Rhodobacter sp was also accumulated, indicating better denitrification process for total nitrogen removal. This study provided evidence for the efficiency of adding MsP to MBR in order to suppress membrane fouling and improve nitrogen removal for low carbon/nitrogen municipal wastewater treatment.

A tailored and rapid approach for ozonation catalyst design

Catalytic ozonation is widely employed in advanced wastewater treatment owing to its high mineralization of refractory organics. The key to high mineralization is the compatibility between catalyst formulation and wastewater quality. Machine learning can greatly improve experimental efficiency, while fluorescence data can provide additional wastewater quality information on the composition and concentration of organics, which is conducive to optimizing catalyst formulation. In this study, machine learning combined with fluorescence spectroscopy was applied to develop ozonation catalysts (Mn/γ-Al2O3 catalyst was used as an example). Based on the data collected from 52 different catalysts, a machine-learning model was established to predict catalyst performance. The correlation coefficient between the experimental and model-predicted values was 0.9659, demonstrating the robustness and good generalization ability of the model. The range of the catalyst formulations was preliminarily screened by fluorescence spectroscopy. When the wastewater was dominated by tryptophan-like and soluble microbial products, the impregnation concentration and time of Mn(NO3)2 were less than 0.3 mol L−1 and 10 h, respectively. Furthermore, the optimized Mn/γ-Al2O3 formulation obtained by the model was impregnation with 0.155 mol L−1 Mn(NO3)2 solution for 8.5 h and calcination at 600 °C for 3.5 h. The model-predicted and experimental values for total organic carbon removal were 54.48% and 53.96%, respectively. Finally, the improved catalytic performance was attributed to the synergistic effect of oxidation (•OH and 1O2) and the Mn/γ-Al2O3 catalyst. This study provides a rapid approach to catalyst design based on the characteristics of wastewater quality using machine learning combined with fluorescence spectroscopy.

The Potential Influence of Advanced Glycation End Products and (s)RAGE in Rheumatic Diseases.

Advanced glycation end products (AGEs) are a class of compounds formed by nonenzymatic interactions between reducing sugars and proteins, lipids, or nucleic acids. AGEs can alter the protein structure and activate one of their receptors, specifically the receptor for advanced glycation end products (RAGE). These phenomena impair the functions of cells, extracellular matrix, and tissues. RAGE is expressed by a variety of cells and has been linked to chronic inflammatory autoimmune disorders such as rheumatoid arthritis, systemic lupus erythematosus, and Sjögren's syndrome. The soluble (s)RAGE cleavage product is a positively charged 48-kDa cleavage product that retains the ligand binding site but loses the transmembrane and signaling domains. By acting as a decoy, this soluble receptor inhibits the pro-inflammatory processes mediated by RAGE and its ligands. In the present review, we will give an overview of the role of AGEs, sRAGE, and RAGE polymorphisms in several rheumatic diseases. AGE overproduction may play a role in the pathogenesis and is linked to accelerated atherosclerosis. Low serum sRAGE concentrations are linked to an increased cardiovascular risk profile and a poor prognosis. Some RAGE polymorphisms may be associated with increased disease susceptibility. Finally, sRAGE levels can be used to track disease progression.

Characterization of DOM and disinfection by-products precursors in biological activated carbon filter backwash water from drinking water treatments

Abstract Biological activated carbon filter backwash water (BAC FBW) removes pollutants from BAC filters in drinking water treatment plants. Characterizing the dissolved organic matter (DOM) in BAC FBW is of great significance for the recycling and treatment of backwash water. DOM pollution was monitored over a year using three-dimensional excitation–emission matrix fluorescence spectra. The dissolved organic carbon (DOC) concentration and fluorescence results showed that the DOC concentration reached the lowest value of 1.95 mg/L in the summer. The relative abundances of fluorescence components had a direct relationship with temperature variations. The soluble microbial products were enhanced greatly during cold seasons, while fulvic-acid-like and humic-acid-like compounds remained constant. Disinfection by-products (DBPs) formation potential and cytotoxicity were evaluated. The total haloacetonitriles (HANs), trihalomethanes (THMs), halonitromethanes (HNMs), and haloacetaldehyde (HALs) formation potentials ranged from 35.5 to 47.3 μg/L, 95.1 to 126 μg/L, 4.95 to 8.06 μg/L, and 43.4 to 53.0 μg/L in BAC FBW, respectively. Among all DBPs included in the calculation, the order of contribution to cytotoxicity was HANs > HALs > THMs > HNMs, respectively. Especially, HANs were much higher than the other DBPs, which should be controlled to avoid the biological risk of effluent quality.

Removal effect of trihalomethanes (THMs) and halogenated acetic acids (HAAs) precursors in reclaimed water by polyaluminum chloride (PACl) coagulation.

This study analyzed the removal effect of various doses of polyaluminum chloride (PACI) on wastewater treatment plants at pH 7. The sewage plant's secondary effluent organic matter (EfOM) separates into four components: hydrophobic base (HOB), hydrophilic (HI), hydrophobic acid (HOA), and hydrophobic neutral (HON). The removal effect for various forms of organic waste is optimum at 16 mg/L and that halogenated acetic acids (HAAs) and trihalomethanes (THMs) are formed simultaneously. After PACI treatment, hydrophobic organic compounds were converted to humic acid (HA), fulvic acid (FA), soluble microbial products (SMPs), and other HI organic compounds, increasing the amount of HAAs produced by HI fractions. Removal rate of hydrophobic organic compounds, particularly HON, is 92.8% when using PAC. Moreover, after EfOM coagulation, most HAAs are trichloroacetic acid (TCAA), followed by bromochloroacetic acid (BCAA) and bromodichloroacetic acid (BDCAA). Only HOB can produce monochloroacetic acid (MCAA), whereas HA and SMPs with HOA are primary components of dichloroacetic acid (DCAA). The toughest removable byproduct of THMs is CHBr3, and after condensation of each THM component, only HOA and HON produce CHBr3, while HI produces only a minimal quantity of CHBrCl2 and CHCl3.This finding is critical for understanding how disinfection byproducts are produced after chlorinating EfOM.

The impact of sunlight on fouling behaviors and microbial communities in membrane bioreactors

Membrane fouling is a significant obstacle to applying membrane bioreactors (MBRs) for wastewater treatment. Here we report the impact of sunlight irradiation on membrane fouling, biopolymers, signal molecules, and microbial communities in MBRs. The degradation of signal molecules, which induce membrane biofouling, occurred through solar photolysis in batch tests. However, MBR sludge exposed to sunlight exhibited different biological behaviors creating more soluble microbial products (SMP) and signal molecules (particularly autoinducer-2). Cell lysis and deflocculation occurred when the MBR mixed liquor was exposed to sunlight. MBR fouling rates coincided with the temporal concentration profiles of SMP and signal molecules. Sunlight caused drastic changes in the MBR microbial community, stimulating the preferential growth of specific bacteria (e.g., Deinococcus Runella, Flavitalea, Glaiimonas, and Rurimicrobium). The nonmetric multidimensional scaling analysis of the MBR community structures with and without sunlight irradiation showed two distinct microbial community clusters and their reversibility. Network analysis based on Spearman's rank correlations revealed that with sunlight irradiation, fouling rates had significant positive connections with SMP proteins and the Flavitalea genus. The findings of this study demonstrate that sunlight is a considerable factor affecting membrane fouling and microbial ecology in MBRs, needing shade for fouling mitigation and sustainable operation.

Trem2 H157Y increases soluble TREM2 production and reduces amyloid pathology

BackgroundThe rare p.H157Y variant of TREM2 (Triggering Receptor Expressed on Myeloid Cells 2) was found to increase Alzheimer’s disease (AD) risk. This mutation is located at the cleavage site of TREM2 extracellular domain. Ectopic expression of TREM2-H157Y in HEK293 cells resulted in increased TREM2 shedding. However, the physiological outcomes of the TREM2 H157Y mutation remain unknown in the absence and presence of AD related pathologies.MethodsWe generated a novel Trem2 H157Y knock-in mouse model through CRISPR/Cas9 technology and investigated the effects of Trem2 H157Y on TREM2 proteolytic processing, synaptic function, and AD-related amyloid pathologies by conducting biochemical assays, targeted mass spectrometry analysis of TREM2, hippocampal electrophysiology, immunofluorescent staining, in vivo micro-dialysis, and cortical bulk RNA sequencing.ResultsConsistent with previous in vitro findings, Trem2 H157Y increases TREM2 shedding with elevated soluble TREM2 levels in the brain and serum. Moreover, Trem2 H157Y enhances synaptic plasticity without affecting microglial density and morphology, or TREM2 signaling. In the presence of amyloid pathology, Trem2 H157Y accelerates amyloid-β (Aβ) clearance and reduces amyloid burden, dystrophic neurites, and gliosis in two independent founder lines. Targeted mass spectrometry analysis of TREM2 revealed higher ratios of soluble to full-length TREM2-H157Y compared to wild-type TREM2, indicating that the H157Y mutation promotes TREM2 shedding in the presence of Aβ. TREM2 signaling was further found reduced in Trem2 H157Y homozygous mice. Transcriptomic profiling revealed that Trem2 H157Y downregulates neuroinflammation-related genes and an immune module correlated with the amyloid pathology.ConclusionTaken together, our findings suggest beneficial effects of the Trem2 H157Y mutation in synaptic function and in mitigating amyloid pathology. Considering the genetic association of TREM2 p.H157Y with AD risk, we speculate TREM2 H157Y in humans might increase AD risk through an amyloid-independent pathway, such as its effects on tauopathy and neurodegeneration which merit further investigation.

Fast Upcycling of Poly(ethylene terephthalate) into Catalyst-Free Vitrimers

We reported a catalyst-free technique to fabricate transesterification-based poly(ethylene terephthalate) (PET) vitrimers via melt reacting PET with N,N′-tetraglycidyldiaminodiphenyl methane (TGDDM) in several minutes. We investigated the effect of TGDDM content on the reaction mechanism and chemical structure of the final products in detail. At low TGDDM content (≤0.5 wt %), branched thermoplastic PET was obtained by the chain-extension reaction between carboxyl groups of PET and epoxy groups of TGDDM. At medium TGDDM content (0.7–1.0 wt %), PET vitrimers with relatively low cross-link density were achieved through the cross-linking reaction between original carboxyl plus hydroxyl groups of PET and epoxy groups of TGDDM. At high TGDDM content (1.2–2.0 wt %), soluble chain-extended products were first formed through reacting original carboxyl and hydroxyl groups of PET with part of epoxy groups of TGDDM, and PET vitrimers were then obtained after the excess epoxy groups were consumed by the newly formed functional groups, which were generated by thermal decomposition of ester groups of PET under catalyzation of tertiary amines of TGDDM moieties. The cross-linked network structure endowed the PET vitrimers with enhanced heat resistance and creep resistance. The obtained PET vitrimers could relax stress rapidly and showed excellent processability and weldability, owing to the fast transesterification between hydroxyl and ester groups under catalyzation of internal tertiary amines. We believe that the facile fabrication technique showed great potentiality for upcycling of PET into vitrimers in large-scale production.

Spectrophotometric Determination of Cefixime by Oxidative Coupling Reaction with 4-Aminophenol in the Presence of Potassium periodate

This work involves a new simple, rapid and sensitive spectrophotometric method for the determination of Cefixem. The method based on the oxidative coupling reaction between Cefixime and 4-Aminophenol using Potassium periodate as oxidizing agent to form a violet color water soluble product that has a maximum absorption at 537 nm. The optimum conditions were:, pH 6.5, temperature between 25-30 oC. Beer’s law is obeyed in a concentration range of 4 to 30 µg / ml with a molar absorptivity of 6749.75 L.mol-1. cm-1. The relative error was 0.729 to - 0.752 % and a relative standard deviation of 0.556 to 0.861% ,DL= 0.136 µg / ml. The proposed method has been successfully applied to the determination of Cefixime in SAMAXIME Capsules with recovery of not less than 98.1%.

Critical role of extracellular DNA in the establishment and maintenance of anammox biofilms

Anaerobic ammonium oxidation (anammox) has been widely used for the sustainable removal of nitrogen from wastewater. Extracellular DNA (exDNA), as one of the main components of biofilms, not only determines the initial formation process, but also allows the three-dimensional structure to be maintained. Since the effects of exDNA on anammox biofilm formation are still poorly understood, this study elucidated the effects of exDNA on different stages of anammox biofilm establishment and maintenance under static conditions and its mechanism. The results revealed that exDNA mainly affected the maintenance stage of anammox biofilm formation. Compared with the absence of exDNA, nitrogen removal efficiency in the presence of exDNA was 6.17 % higher; the number of bacteria cells attached to the carrier was 2.23 times that in the absence of exDNA. The spatiotemporal distribution of bacteria was revealed by fluorescence in situ hybridization. After 30 days, the relative abundances of anammox in biofilms were 6.19 % and 0.4 % in the presence and absence of exDNA, respectively, indicating its positive role in anammox bacteria (AnAOB) adhesion and biofilm formation. The presence of exDNA in extracellular polymeric substances (EPS) promotes the synthesis of proteins and soluble microbial products. According to the extended Derjaguin−Landau−Verwey−Overbeek (X − DLVO) theory, the presence of exDNA also reduced the Lewis acid–base interaction energy and created favorable thermodynamic conditions for AnAOB adhesion. These findings advance our understanding of the role of exDNA in anammox-mediated biofilm formation and offer insights into the mechanism of exDNA in the establishment and maintenance stages.

Synergistic effects of simultaneous coupling ozonation and biodegradation for coking wastewater treatment: Advances in COD removal, toxic elimination, and microbial regulation

Coking wastewater contains high concentrations of cyanide, phenols, pyridine, quinoline, and polycyclic aromatic hydrocarbons. Its high toxicity and low biodegradability leads to long hydraulic retention time of biological process and high cost of advanced oxidation process. In this study, the simultaneous combination of ozonation and biodegradation (SCOB) was proposed to treat coking wastewater. Through this process, ozonation breaks the refractory organics, and the biodegradable intermediates are rapidly mineralized by microorganisms protected by porous carriers. Thus, the performances of SCOB, individual biodegradation and ozonation systems were compared. The long-term stability of the SCOB system was evaluated, the contributions of ozonation and biodegradation were analyzed, and their synergistic mechanisms were elaborated. Results showed that biological activity was inhibited in the biodegradation system, and chemical oxygen demand (COD) removal was only 27.6% for the ozonation system. COD and total phenol removal of SCOB system reached 48.5% and 79.3%, respectively, and its kinetic degradation constant of COD was 55.6% higher than that of the ozonation system. Ozonation contributed to the oxidation of organics with unsaturated functional groups as well as soluble microbial products (SMPs), causing the effluent toxicity and chroma to decrease by 82.7% and 270 times, respectively. The higher abundances of microorganisms and functions were enriched in the core of carrier, which became dominant region for biodegradation. Consequently, COD removal of the SCOB system stabilized at >80% for real coking wastewater treatment, confirming its promising potential for the treatment of highly polluted industrial wastewater.

Effect of branching in zwitterionic polymer brushes grafted from PES UF membrane surfaces via AGET-ATR(c)P

This research explored the relationship between the antifouling behavior of porous ultrafiltration (UF) membranes and linear or branched brushes adorning their surfaces. Polyethersulfone UF membranes were functionalized via one-pot lithiation/acylation to enable surface-initiated activators generated by electron transfer for atom transfer radical (co)polymerization of sulfobetaine methacrylate (SBMA) and N,N′-methylenebisacrylamide (MBAm). Changing the SBMA/MBAm ratio and polymerization time grafted brushes at different branching and thicknesses. Surface analyses verified differences in brush architecture and that the degree of grafting increased with grafting time – it was higher for linear brushes than branched ones. Colloidal probe lateral force atomic force microscopy (LFM) showed ideal hydration–lubrication propensity of the lower branching degree poly(SBMA-co-MBAm) over pristine, linear poly(SBMA), and higher branching poly(SBMA-co-MBAm)-grafted membranes. Sharp-tip LFM predicted a critical size of <15 nm for penetrating the branched brush layers. Fouling experiments with bovine serum albumin (∼10 nm) and dextran (∼18 nm) revealed that linear and branched modifications had significantly less fouling than the pristine membrane. An optimal degree of branching can limit foulant adsorption, but fouling could be enhanced if the polymers' hydration capacity was diminished relative to a less dense network. Fouling experiments with soluble microbial products further demonstrated the branched membrane's high antifouling activity.

Insight into the effects and mechanism of cellulose and hemicellulose on anaerobic digestion in a CSTR-AnMBR system during swine wastewater treatment

The cellulose and hemicellulose content in swine wastewater significantly affected the performance of a continuous stirred tank reactor-anaerobic membrane bioreactor (CSTR-AnMBR). When the influent content of cellulose and hemicellulose was controlled at 3.88 ± 0.89 and 9.72 ± 2.05 g/L, respectively, the CSTR-AnMBR showed a low methane yield (0.04–0.06 L CH4/g COD) at both HRT of 12 d and HRT 30 d. The functional microbes preferred to use the freshly added degradable COD, and the decomposition of refractory COD was paused. Meanwhile, the AnMBR unit was troubled by rapidly growing membrane fouling. The trans-membrane pressure increased with a rate of 1.63 kPa/d (HRT = 12d), and 0.99 kPa/d (HRT = 30 d) exacerbated the reactor performance. In high cellulose and hemicellulose-containing environments, the cellulolytic and hemicellulolytic microbes, including Bacteroidetes and Proteobacteria, were stimulated to a certain extent. In addition, cellulose and hemicellulose up-regulated the gene expression for sugar and amino acid metabolism, decreasing the abundance of metabolism related to methane production. When the influent content of cellulose and hemicellulose decreased to 0.62 ± 0.12 and 0.77 ± 0.30 g/L, respectively, the system's performance was significantly improved, microorganisms produced less low-molecular-weight soluble microbial products, which also reduced membrane fouling risk. This study provides significant guidance for treating livestock manure with the CSTR-AnMBR system.

Investigating the effects of cyclic topology on the performance of a plastic degrading enzyme for polyethylene terephthalate degradation

Agitation is a commonly encountered stress for enzymes during all stages of production and application, but investigations that aim to improve their tolerance using topological engineering have yet to be reported. Here, the plastic-degrading enzyme IsPETase was cyclized in a range of topologies including a cyclic monomer, cyclic dimer and catenane using SpyTag/SpyCatcher technologies, and their tolerance towards different stresses including mechanical agitation was investigated. The cyclic dimer and catenane topologies were less susceptible to agitation-induced inactivation resulting in enhancement of polyethylene terephthalate (PET) degradation. While contrary to conventional belief, cyclic topologies did not improve tolerance of IsPETase towards heat or proteolytic treatment, the close proximity of active sites in the dimeric and catenane variants was found to enhance PET conversion into small soluble products. Together, these findings illustrate that it is worthwhile to explore the topology engineering of enzymes used in heterogeneous catalysis as it improves factors that are often overlooked in homogeneous catalysis studies.

A Highly Reversible Lithium–Carbon Dioxide Battery Based on Soluble Oxalate

Li–CO2 batteries that integrate energy storage with CO2 fixation are expected to be a promising technology in the pursuit of carbon neutrality. However, cathode passivation and structural damage caused by the solid discharge product Li2CO3 are major challenges hindering the practical implementation of Li–CO2 batteries. To address these challenges, herein, a breakthrough Li–CO2 battery leading to a soluble and easily-decomposed discharge product, C2O42–, driven by regulating the solvation sheath of Li+, has been achieved by introducing the high-polarity dimethyl sulfoxide electrolyte. Experimental results and theoretical calculations show that the increased Li+ interaction and electrolyte molecule can induce the solution-phase formation of stabilized C2O42–, while simultaneously suppressing direct reduction of CO2 to Li2CO3. The tough problems with Li–CO2 batteries caused by solid products are effectively solved by production of soluble C2O42–, which provides a promising solution for research on non-aqueous metal–air batteries.