Soluble Products Research Articles

Is Oral Vaccination against Escherichia coli Influenced by Zinc Oxide?

Although zinc oxide has been banned at therapeutic doses in the EU, its use is still legal in most countries with industrial pig farming. This compound has been shown to be very effective in preventing E. coli-related diseases. However, another strategy used to control this pathogen is vaccination, administered parenterally or orally. Oral vaccines contain live strains, with F4 and F18 binding factors. Since zinc oxide prevents E. coli adhesion, it is hypothesised that its presence at therapeutic doses (2500 ppm) may alter the immune response and the protection of intestinal integrity derived from the vaccination of animals. A group of piglets were orally vaccinated at weaning and divided into two subgroups; one group was fed a feed containing 2500 ppm zinc oxide (V + ZnO) for the first 15 days post-vaccination (dpv) and the other was not (V). Faeces were sampled from the animals at 6, 8, 11, 13, and 15 dpv. Unvaccinated animals without ZnO in their feed (Neg) were sampled simultaneously and, on day 15 post-vaccination, were also compared with a group of unvaccinated animals with ZnO in their feed (ZnO). Differences were found in E. coli excretion, with less quantification in the V + ZnO group, and a significant increase in secretory IgA in the V group at 8 dpv, which later equalised with that of the V + ZnO group. There was also some difference in IFNα, IFNγ, IL1α, ILβ, and TNFα gene expression when comparing both vaccinated groups (p < 0.05). However, there was no difference in gene expression for the tight junction (TJ) proteins responsible for intestinal integrity. Although some differences in the excretion of the vaccine strain were found when comparing both vaccinated groups, there are no remarkable differences in immune stimulation or soluble IgA production when comparing animals orally vaccinated against E. coli in combination with the presence or absence of ZnO in their feed. We can conclude that the immune response produced is very similar in both groups.

Endoglucanase effects on energy consumption in the mechanical fibrillation of cellulose fibers into nanocelluloses

Enzymatic processing is considered a promising approach for advancing environmentally friendly industrial processes, such as the use of endoglucanase (EG) enzyme in the production of nanocellulose. However, there is ongoing debate regarding the specific properties that make EG pretreatment effective in isolating fibrillated cellulose. To address this issue, we investigated EGs from four glycosyl hydrolase (GH) families (5, 6, 7, and 12) and examined the roles of the three-dimensional structure and catalytic features, with a focus on the presence of a carbohydrate binding module (CBM). Using eucalyptus Kraft wood fibers, we produced cellulose nanofibrils (CNFs) through mild enzymatic pretreatment, followed by disc ultra-refining. Comparing the results with the control (without pretreatment), we observed that GH5 and GH12 enzymes (without CBM) reduced fibrillation energy by approximately 15 %. The most significant energy reduction, 25 and 32 %, was achieved with GH5 and GH6 linked to CBM, respectively. Notably, these CBM-linked EGs improved the rheological properties of CNF suspensions without releasing soluble products. In contrast, GH7-CBM exhibited significant hydrolytic activity, resulting in the release of soluble products, but did not contribute to a reduction in fibrillation energy. This discrepancy can be attributed to the large molecular weight and wide cleft of GH7-CBM, which led to the release of soluble sugars but had little impact on fibrillation. Our findings suggest that the improved fibrillation observed with EG pretreatment is primarily driven by efficient enzyme adsorption on the substrate and modification of the surface viscoelasticity (amorphogenesis), rather than hydrolytic activity or release of products.

Evaluating the potential of off-line methodologies to determine sludge filterability from different municipal wastewater treatment systems

This study aimed to evaluate the capability of different methodologies for determining sludge filterability and estimate filtration resistance during real filtration processes. Three filterability methods were applied during this study: capillary suction time (CST), time to filter (TTF), and specific resistance to filtration (SRF). These methods were evaluated using three different sludge sources: aerobic activated sludge, supernatant from a primary settler further concentrated by ultrafiltration membranes (PSE), and digestate from the anaerobic co-digestion of microalgae and primary sludge. These sludge sources were taken from systems treating municipal wastewater entering to a full-scale wastewater treatment facility. The capability of CST, TTF and SRF to estimate total suspended solids (TSS) and soluble microbial products (SMP) concentrations was also assessed, while validating the results obtained with the real filtration process of the operated membrane-based systems. The results suggested that both TSS and SMP concentrations significantly affect filterability. However, each sludge filterability was mainly dominated by one of these parameters (TSS or SMP), being the biological sludge more influenced by the SMP content, while the PSE filterability was mainly controlled by the TSS concentration. SRF method resulted in poor correlations between filterability and TSS and SMP concentrations, especially regarding SMP. CST method resulted in good correlations for all treated sludge regardless the TSS and SMP concentration. However, when treating sludge without an important biological activity (e.g. PSE), TTF method was identified as the best option due to its better correlation with the experimentally determined sludge filtration resistance.

Effects of raw water quality on the adsorptive removal of 2-methylisoborneol by powdered activated carbon under non-equilibrium conditions

Abstract Natural organic matter contained in natural water inhibits the adsorptive removal of 2-methylisoborneol (2-MIB) by powdered activated carbon (PAC). We investigated the relationship between water-quality indices and the adsorptive removal of 2-MIB by PAC. We collected three different raw water (i.e., two lake water and one river water) samples twice per month for 10 months. We characterized the raw water using total organic carbon concentration, ultraviolet absorption at 254 nm, electrical conductivity, and excitation–emission matrix analysis. The results were compared with 2-MIB removal rates evaluated from PAC adsorption experiments and revealed that there was no universal indicator that could explain the trends of the 2-MIB removal rate during the overall experimental period. The correlation trends between 2-MIB removal rates and water-quality indices differed significantly between the high and low water-temperature periods. Several water-quality indices related to the organic matter associated with biological processes, especially algal activities (i.e., soluble microbial products, chlorophylls, and phycocyanin), exhibited significant correlations with the 2-MIB removal rates (|R| &amp;gt; 0.7) under certain conditions (e.g., high lake-water temperature). Both the parallel factor (PARAFAC) analysis and fluorescence regional integration (FRI) method could evaluate such behaviors after including the regions associated with algal organic matter in the calculation.

Subcritical water hydrolysis of chia seed proteins and their functional characteristics

Deoiled chia flour is an important protein-rich by-product of the chia oil industry. This work used green process subcritical water hydrolysis to hydrolyse chia seed protein from deoiled chia flour and compared it with alkali hydrolysis. The yields of total protein, total amino acids, and reducing sugars in the soluble hydrolysate products were examined in relation to the effects of the extraction conditions (reaction time and temperature). Hydrolysates generated at 225 °C after 30 min of hydrolysis exhibited the highest protein content (213.76 ± 0.44 mg/g of chia protein concentrate) and total free amino acid content (44.26 ± 0.79 mg/g of chia protein concentrate), while the highest extent of extraction (62.72 ± 1%), and degree of hydrolysis (13.85 ± 0.50%) was observed at 200 °C after 30 min of hydrolysis. Alkali hydrolysis exhibited significantly (p < 0.05) lower protein hydrolysis (10.66 ± 0.51%) and total free amino acids (22.66 ± 0.53 mg/g of CPC) than subcritical water hydrolysis. SEM, elemental analysis and XRD conferred the degradation of CPC and provided strong evidence in supporting subcritical water hydrolysis for chia seeds. Subcritical water hydrolysates can be envisioned to develop functional foods from chia seeds.

Evaluation of Efficiently Removing Secondary Effluent Organic Matters (EfOM) by Al-Based Coagulant for Wastewater Recycling: A Case Study with an Industrial-Scale Food-Processing Wastewater Treatment Plant.

The reuse of wastewater has been identified as an important initiative for the sustainable development of the environment; thus, the removal of secondary effluent organic matter (EfOM) to ensure the safety of reused wastewater is the key step and a subject of extensive research. In this study, Al2(SO4)3 and anionic polyacrylamide were selected as coagulant and flocculant, respectively, for the treatment of secondary effluent from a food-processing industry wastewater treatment plant to meet the standard regulatory specifications for water reuse. In this process, the removal efficiencies of chemical oxygen demand (COD), components with UV254, and specific ultraviolet absorbance (SUVA) were 44.61%, 25.13%, and 9.13%, respectively, with an associated reduction in chroma and turbidity. The fluorescence intensities (Fmax) of two humic-like components were reduced during coagulation, and microbial humic-like components of EfOM had a better removal efficiency because of a higher Log Km value of 4.12. Fourier transform infrared spectroscopy showed that Al2(SO4)3 could remove the protein fraction of the soluble microbial products (SMP) of EfOM by forming a loose SMP protein complex with enhanced hydrophobicity. Furthermore, flocculation reduced the aromaticity of secondary effluent. The cost of the proposed secondary effluent treatment was 0.034 CNY t-1 %COD-1. These results demonstrate that the process is efficient and economically viable for EfOM removal to realize food-processing wastewater reuse.

A common mechanism of Sec61 translocon inhibition by small molecules.

The Sec61 complex forms a protein-conducting channel in the endoplasmic reticulum membrane that is required for secretion of soluble proteins and production of many membrane proteins. Several natural and synthetic small molecules specifically inhibit Sec61, generating cellular effects that are useful for therapeutic purposes, but their inhibitory mechanisms remain unclear. Here we present near-atomic-resolution structures of human Sec61 inhibited by a comprehensive panel of structurally distinct small molecules-cotransin, decatransin, apratoxin, ipomoeassin, mycolactone, cyclotriazadisulfonamide and eeyarestatin. All inhibitors bind to a common lipid-exposed pocket formed by the partially open lateral gate and plug domain of Sec61. Mutations conferring resistance to the inhibitors are clustered at this binding pocket. The structures indicate that Sec61 inhibitors stabilize the plug domain in a closed state, thereby preventing the protein-translocation pore from opening. Our study provides the atomic details of Sec61-inhibitor interactions and the structural framework for further pharmacological studies and drug design.

Xylanase-assisted adsorption process for high purity sugar stream development from hydrolysis liquor of kraft-based dissolving pulp production process

This paper proposed a novel xylanase-assisted activated carbon process to produce a high-purity sugar stream from pre-hydrolysis liquid (PHL) of the kraft-based dissolving pulp production process. The results showed that the enzymatic hydrolysis could effectively improve the lignin removal and sugar purity at pH 5 and 50 °C. It was observed that the cleavage of lignin-carbohydrate complex (LCC) by enzyme led to more sugar and soluble lignin production in PHL. The main mechanisms involved are the reduced pore clog due to the lignin converted from colloidal to dissolved state at higher pH, lower sugar loss obtained by the reduction of polymerization degree of poly-sugars in PHL and also the removal of the lignin disconnected from the LCC. FTIR NMR, particle size, BET, and SEM analyses confirmed that the induced soluble lignin could be adsorbed by activated carbon effectively without blocking its pores, which improved the selectivity and productivity of activated carbon for removing lignin and generating higher purity sugar stream (97.5 wt. %). Based on the promising results and simplicity of the proposed operations, the introduced process may be attractive to the industry for generating high-purity sugars at an industrial scale.

Cationic polymer precipitation for enhanced impurity removal in downstream processing.

Precipitation can be used for the removal of impurities early in the downstream purification process of biologics, with the soluble product remaining in the filtrate through microfiltration. The objective of this study was to examine the use of polyallylamine (PAA) precipitation to increase the purity of product via higher host cell protein removal to enhance polysorbate excipient stability to enable a longer shelf life. Experiments were performed using three monoclonal antibodies (mAbs) with different properties of isoelectric point and IgG subclass. High throughput workflows were established to quickly screen precipitation conditions as a function of pH, conductivity and PAA concentrations. Process analytical tools (PATs) were used to evaluate the size distribution of particles and inform the optimal precipitation condition. Minimal pressure increase was observed during depth filtration of the precipitates. The precipitation was scaled up to 20L size and the extensive characterization of precipitated samples after protein A chromatography showed >75% reduction of host cell protein (HCP) concentrations (by ELISA),>90% reduction of number of HCP species (by mass spectrometry), and >99.8% reduction of DNA. The stability of polysorbate containing formulation buffers for all three mAbs in the protein A purified intermediates was improved at least 25% after PAA precipitation. Mass spectrometry was used to obtain additional understanding of the interaction between PAA and HCPs with different properties. Minimal impact on product quality and <5% yield loss after precipitation were observed while the residual PAA was <9 ppm. These results expand the toolbox in downstream purification to solve HCP clearance issues for programs with purification challenges, while also providing important insights into the integration of precipitation-depth filtration and the current platform process for the purification of biologics.

Insight into the corrosion resistance of Mo-added NiCrBSi coating in simulated waste incineration environment

The corrosion resistance of Ni40AA and Ni40AA-Mo coatings on 304SS substrate was evaluated in molten NaCl-Na2SO4-KCl-K2SO4 salts at 600 ℃. In the oxidizing-chloridizing environment, results showed that Cr or Cr-rich oxides would react with molten salts and generate chlorides or chromates (Na2Cr2O4; K2CrO4). After adding Mo, the dissolved Cr in soluble corrosion products was significantly reduced. Mo substituted Cr to react with molten salts and reduced the depletion of Cr, which benefited the accumulation of Cr-rich oxides. Therefore, adding Mo enhanced the corrosion resistance of Ni40AA, reducing the corrosion weight gain by approx. 50% and the thickness loss by 1/3.

Anaerobic membrane bioreactor for real antibiotic pharmaceutical wastewater treatment: Positive effect of fouling layer on antibiotics and antibiotic resistance genes removals

Anaerobic membrane bioreactor (AnMBR) is a potential candidate for high-strength pharmaceutical wastewater treatment. However, its contribution to reduce the antibiotic and antibiotic resistance genes (ARGs) is still largely unclear. Herein, this study investigated the antibiotics and ARGs removal in AnMBR for real high-strength antibiotic (levofloxacin (LEV)) pharmaceutical wastewater treatment, focusing on the positive effect of membrane fouling layers (biofilms). Results indicated that membrane biofilm has a positive effect on AnMBR treatment with improved COD and LEV removal efficiency by 12% and 10%, respectively. This might be ascribed to the enhanced biodegradation ability of the organic matter by the biofilm due to the enrichment of fermentation bacteria (Anaerobium), hydrogen-producing bacteria (Clostridium_sensu_stricto_1) and hydrogenotrophic methanogenic archaea (Methanobacterium and Methanobrevibacter). Importantly, the membrane biofilm can also effectively mitigate the ARGs (qnrS, qnrA) and class 1 integrator (intI1) dissemination and the absolute abundance of ARGs in the medium fouling (MF) biofilm effluent was 0.27 orders of magnitude lower than that of low fouling (LF) biofilm effluent. This can be explained by the variation of membrane surface becoming more hydrophobic in MF than LF biofilm with increased contact angle and more negative surface zeta potential, suggesting higher adsorption and adhesion properties. The strong correlation between extracellular polymer substance (EPS) and soluble microbial product (SMP) contents and qnrA, qnrS and intI1 further indicated the important role of EPS and SMP in membrane biofilm on ARGs reduction. Furthermore, the entrapment of ARGs potential hosts bacteria of Comamonas and Enterococcus with high biofilm formation potential also attributed to the improved ARGs removal with the increase of membrane fouling degree. Our findings suggest that AnMBR is effective for antibiotic pharmaceutical wastewater treatment and membrane biofilm has a positive effect on antibiotic and ARGs removal, which promotes the AnMBR application in the pharmaceutical industry.

Molecular insights towards changing behaviors of organic matter in a full-scale water treatment plant using FTICR-MS

The changing behavior of organic matter in a full-scale water treatment process was characterized based on the three-dimensional excitation-emission matrix (3D-EEM) and Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS). Polyaluminum chloride (PAC) as a coagulant can help to effectively remove soluble microbial by-products-like and aromatic protein-like substances during coagulation and sedimentation, corresponding to tannin and coagulated aromatic regions. The leakage of soluble microbial products during sand filtration resulted in an increase in the intensity of biomass-like regions. Nitrogen-containing compounds have higher weighted average value of double bond equivalents (DBEw) and the modified aromaticity index (AImod-w) than nitrogen-free compounds. Water treatment can preferentially remove unsaturated nitrogen-containing compounds with more O atoms and higher-oxidation-state carbon. The dissolved organic carbon (DOC) and UV254 were not correlated well with changes in nitrogen-containing compounds due to the preferential removal of nitrogen-containing compounds. This study revealed the specificity of organic matter removal during water treatment, and it was helpful in optimizing treatment processes for various raw water to ensure water quality.

Fouling and clogging behavior of porous membrane during biogas recovery from submerged granular anaerobic membrane bioreactor permeate; long-term stability analysis

This work investigated the fouling and clogging behavior of the porous polypropylene (PP) membrane during the long-term (1032 h.) biogas recovery operation of the ultrafiltration effluent discharged from an in-house granular anaerobic membrane bioreactor (G-AnMBR) unit. The study implemented different cleaning strategies, evaluated performance loss and recovery due to fouling and cleaning, and characterized the fouling. The normalized CH4 flux dropped by 54 % while the liquid pressure drop increased from 10 to 800 mbar after 312 h. operation. Acid cleaning (AC) with citric acid solution was found to be very effective in removing both reversible and irreversible fouling and restoring the initial membrane performance. Ca2+, and CO32−, were found to be the major inorganic fouling elements. The organic fouling consisted of 79 % aromatic proteins, 17 % fulvic-like substances, and 4 % soluble microbial products. Evidence of biofouling was confirmed by COD and DOC analysis and by detecting nucleic acids in the FTIR analysis.

Comparative study on biohydrogen production by newly isolated Clostridium butyricum SP4 and Clostridium beijerinckii SP6

The hydrogen-producing bacteria SP4 and SP6 were isolated from the compost and identified by 16S rRNA gene sequencing as Clostridium butyricum and Clostridium beijerinckii, respectively. A comparative study on the biohydrogen-producing activity of the isolated strains was carried out using mono-, di- and tri-saccharides belonging to both hexoses (maltose, glucose, mannose, fructose, lactose, galactose, sucrose, raffinose, cellobiose) and pentoses (xylose). To assess the biotechnological significance, real wastewater rich in sugars (cheese whey, confectionery wastewater, sugar beet processing wastewater) was also used as a substrate. C. butyricum SP4 fermented sugars with a yield of 0.93–1.52 mol H2/mol hexose (pentose); the maximum yield was obtained from fructose, the minimum – from raffinose and cellobiose. The most preferred substrate for C. beijerinckii SP6 was sucrose with a yield of 1.76 mol H2/mol hexose, while cellobiose yielded only 0.64 mol H2/mol hexose. Overall, the efficiency of converting wastewater to H2 by C. butyricum SP4 was also slightly lower (66–93 ml H2/g chemical oxygen demand (COD)) than that of C. beijerinckii SP6 (76–103 ml H2/g COD). Even though the main soluble metabolite products (SMPs) for both isolates were acetate and butyrate, C. butyricum SP4 also produced a significant amount of ethanol (up to 21.5% of SMPs) and formate (up to 32.5% of SMPs), and C. beijerinckii SP6 – lactate (up to 25% of SMPs). A distinctive feature of C. beijerinckii SP6 was a significantly lower (almost 2 times) yield of SMPs, while C. butyricum SP4 had a higher rate of H2 production according to the results obtained from the kinetic study using the modified Gompertz equation and the first order equation. Analysis of Spearman's rank correlation coefficients revealed a statistically significant relationship between the kinetic parameters of H2 production and the concentration of butyrate and the final pH of the medium for C. butyricum SP4, and with the concentration of ethanol for C. beijerinckii SP6. These findings provide valuable information on the metabolic capabilities of the most studied hydrogen-producing representatives of the Clostridium genus for their use in optimizing the technology for biohydrogen production by dark fermentation of various organic wastes.

Complement dependent TNFα production in neutrophil-like HL60 cells

Neutrophils develop in the bone marrow (BM) from hematopoietic stem cells (HSCs) through a series of progenitor cells and mature neutrophils play a critical role in the human immune system. Previous studies revealed that tumor necrosis factor α (TNFα) produced by immature neutrophils contributes to HSCs development and vascular regeneration in the BM niche. However, the precise mechanism of TNFα production in immature neutrophils remains unclear. This study aims to assess the relationship between complement C3 activation and TNFα production from immature neutrophils. We investigated the regulatory mechanism of TNFα production by complement components in neutrophil-like HL60 cells. Flow cytometric analysis showed that C3a receptor (C3aR) and C3bi receptor (CR3, Mac-1, CD11b/CD18, integrin αMβ2) are expressed on the surface of neutrophil-like HL60 cells. We found that zymosan-treated human serum leads to TNFα production in neutrophil-like HL60 cells, but not in human polymorphonuclear cells (PMNs). A C3-convertase inhibitor, compstatin suppresses TNFα production. These data suggest that the TNFα production is mediated by complement C3 activation. Furthermore, the TNFα production is enhanced by Ca2+ elevating agents, thapsigargin (TG), but is suppressed by treatment with Ca2+ chelators, EGTA, or BAPTA-AM. In addition, the soluble TNFα production is suppressed by treatment with immobilized-fibrinogen or -fibronectin. Thus, the TNFα production is enhanced by intracellular Ca2+ elevation and is negatively regulated by the interaction between the neutrophil-like HL60 cells and fibrinogen or fibronectin.

Influence of interspecies interactions on biomass and extracellular polymeric substances of bacterial biofilms

BackgroundStudies with emphasis on pure and mixed-species biofilms are of significant importance in understanding biofilm formation mechanisms during microbial infections. This research aims to evaluate pure- and dual-species biofilms of Escherichia coli (code A), Staphylococcus aureus (code B), Klebsiella pneumoniae (code C) and Pseudomonas aeruginosa (code D) pathogenic bacterial species and their production of biofilm exopolysaccharides at laboratory scale. MethodsBiofilm biomass (A595) of pure- and dual-species cultures was determined by means of a microtiter plate assay in triplicate using a microplate photometer (Fisher Scientific, type-357). Extracellular polymeric substances (EPS) and soluble microbial products (SMP) were extracted from the biofilm cells (pure- and dual-species cultures) using the alkaline-heat extraction method. Dry weights (g/L) of EPS and SMP were determined by drying the samples at 105 °C for 8 hours. ResultsKlebsiella pneumoniae biofilm biomass accounted for a 28-72% greater biofilm biomass than the other bacteria. Experimental values of dual-species biofilm biomasses were in the range of 6% to 30% over theoretical values. The experimental value of one dual-species (bacteria B + D) biofilm biomass was 30% higher than its expected value. Decrease or increase in the dual-species biofilm biomass of either bacteria A+C or bacteria B+C combinations was totally dependent on the cell density of bacteria C. Conclusions Biofilm biomass of pure-species cultures was totally species-dependent, and the biofilm biomass of four species was in the following order: bacteria C &gt; D &gt; A &gt; B. Relation between biofilm biomasses and SMP or EPS was inconsistent.

Rational redesign of thermophilic PET hydrolase LCCICCG to enhance hydrolysis of high crystallinity polyethylene terephthalates

Polyethylene terephthalate (PET)-degrading enzymes represent a promising solution to the plastic pollution. However, PET-degrading enzymes, even thermophilic PETase, can effectively degrade low-crystallinity (∼8%) PETs, but exhibit weak depolymerization of more common, high-crystallinity (30–50%) PETs. Here, based on the thermophilic PETase, LCCICCG, we proposed two strategies for rational redesign of LCCICCG using the machine learning tool, Preoptem, combined with evolutionary analysis. Six single-point mutants (S32L, D18T, S98R, T157P, E173Q, N213P) were obtained that exhibit higher catalytic efficiency towards PET powder than wild-type LCCICCG at 75 °C. Additionally, the optimal temperature for degrading 39.07% crystalline PET increased from 65 °C in the wild-type LCCICCG to between 75 and 80 °C in the LCCICCG_I6M mutant that carries all six single-point mutations. Especially, the LCCICCG_I6M mutant has a significantly higher degradation effect on some commonly used bottle-grade plastic powders at 75–80 °C than that of wild type. The enzymatic digestion of ground 31.30% crystalline PET water bottles by LCCICCG_I6M yielded 31.91 ± 0.99 mM soluble products in 24 h, which was 3.64 times that of LCCICCG (8.77 ± 1.52 mM). Overall, this study provides a feasible route for engineering thermostable enzymes that can degrade high-crystallinity PET plastic.

Evaluation the role of soluble microbial products for denitrification sludge characteristic under starvation stress

Physiological changes with the assist role of soluble microbial products (SMP) of preserved denitrifying sludge (DS) undergoing long-term stress of starvation under different storage temperature is extremely important. In this study, SMP extracted from DS were added into DS in starvation condition under room temperature (15–20 °C), 4 °C and −20 °C with three different bio-augmentation phases of 10, 15 and 30 days. Experimental results showed that added SMP in room temperature was optimal for preservation of DS under starvation stress with optimized dosage of 2.0 mL mL−1 sludge and bio-augmentation phase of 10 d. SMP was more effective in maintaining the specific denitrification activity of DS, and it was nearly boosted to 94.1 % of control one due to assist of 2 times SMP addition with 10 days interval of each. Under assist of SMP, extracellular polymeric substances (EPS) secretion was enhanced as the defense layer to withstand starvation stress, and the protein may be utilized as an alternative substrate to gain energy, accelerate electron transport and transfer during denitrification process. This investigation revealed the feasibility of SMP as an economical and robust strategy for preservation of DS.

Acute impact of salinity and C/N ratio on the formation and properties of soluble microbial products from activated sludge

The present study investigated the shock of NaCl and C/N ratio on properties of soluble microbial products (SMPs), focusing on their sized fractions. The results indicated that the NaCl stress increased the content of biopolymers, humic substances, building blocks, and LMW substances in SMPs, while the addition of 40 g NaCl L−1 significantly changed their relative abundance in SMPs. The acute impact of both N-rich and N-deficient conditions accelerated the secretion of SMPs, but the characteristics of LMW substances differed. Meanwhile, the bio-utilization of SMPs has been enhanced with the increase of NaCl dosage but decreased with the increase of the C/N ratio. The mass balance of sized fractions in SMPs + EPS could be set up when NaCl dosage <10 g/L and C/N ratio >5, which indicates the hydrolysis of sized fractions in EPS mainly compensated for their increase/reduction in SMPs. Besides, the results of the toxic assessment indicated that the oxidative damage caused by the NaCl shock was an important factor affecting the property of SMPs, and the abnormal expression of DNA transcription cannot be neglected for bacteria metabolisms with the change of C/N ratio.

Antibiotic removal from swine farming wastewater by anaerobic membrane bioreactor: Role of hydraulic retention time

This study investigated the impact of hydraulic retention time (HRT) on the removal of veterinary antibiotics by an anaerobic membrane bioreactor (AnMBR) for swine wastewater treatment. Ten commonly used antibiotics in the group of tetracyclines, fluoroquinolones, and sulfonamides were evaluated. Results show that a wide variation from 21 to 99% was observed for antibiotic removal by AnMBR regardless of the applied HRT. The methane yield increased from 0.22 L/g COD to 0.28 L/g COD as the operational HRT was prolonged from 24 to 48 h for AnMBR. Doubling the HRT value enhanced removal of most antibiotics and methane yield by 2–30% and 22–47%, respectively. The enhanced antibiotic removal in response to HRT prolongation could be positively correlated to the enrichment of the genus unidentified_Synergistaceae. Moreover, prolonging HRT increased the relative abundance of the genera unidentified_Synergistaceae, Geobacter and Methanobrevibacter, which could strengthen hydrogenotrophic methanogenesis to enhance methane yield. In addition, HRT increase reduced the ratio of protein to polysaccharide in both extracellular polymeric substances and soluble microbial products, thereby, alleviating membrane fouling in AnMBR operation.