Unraveling the evolution of dissolved organic matter in full-scale A/A/O wastewater treatment process using size exclusion chromatography with PARAFAC and nonnegative matrix factorization analysis.

Changes in spectral features and molecular weight (MW) of dissolved organic matter (DOM) along the A/A/O processes in eight full-scale wastewater treatment plants (WWTPs) were characterized using size exclusion chromatography with a diode array detector, a fluorescence detector and an organic carbon detector in tandem (SEC-DAD-FLD-OCD) as well as bulk water quality parameters. The parallel factor (PARAFAC) and the nonnegative matrix factorization (NMF) analyses have been effectively applied to the postprocessing of SEC-FLD fingerprints and SEC-OCD chromatograms, respectively. Individual SEC-FLD-PARAFAC or SEC-OCD-NMF components may span a broad range of MW, indicating that these SEC fractions within the same component were cognate and varied coherently across the dataset samples. The SEC-FLD-PARAFAC modeling and SEC-OCD-NMF analysis have clearly and concisely presented that the dramatic decreases of dissolved organic carbon, UV absorbance at 254 nm and protein-like fluorescence at Ex280/Em350 nm in the anaerobic process were primarily associated with the degradation of the large MW proteinaceous and polysaccharide-like biopolymers. It has also revealed that fluorescence of humic acid-like fractions increased significantly during the anaerobic process, but fluorescence of fulvic acid-like and humic substances' building blocks decreased slightly. Laboratory experiments further confirmed the presence of the humification process in anaerobic processes, and the formation of humic acid-like fluorophores may be associated with carbohydrate metabolism. The combination of SEC-FLD-PARAFAC and SEC-OCD-NMF helped to establish the links between changes in bulk water quality parameters and the evolution of SEC MW fractions, which provides a more in-depth insight into wastewater DOM treatability and enables the optimization of wastewater treatment processes.

Simultaneous determination of dissolved organic nitrogen, nitrite, nitrate and ammonia using size exclusion chromatography coupled with nitrogen detector.

Accurate quantification of dissolved organic nitrogen (DON) has been a challenge due to the cumulative analytical errors in the conventional method via subtracting dissolved inorganic nitrogen species (DIN) from total dissolved nitrogen (TDN). Size exclusion chromatography coupled with an organic nitrogen detector (SEC-OND) has been developed as a direct method for quantification and characterization of DON. However, the applications of SEC-OND method still subject to poor separations between DON and DIN species and unsatisfied N recoveries of macromolecules. In this study, we packed a series of SEC columns with different lengths and resin materials for separation of different N species and designed an independent vacuum ultraviolet (VUV) oxidation device for complete oxidation converting N species to nitrate. To guarantee sufficient N recoveries, the operation conditions were optimized as oxidation time ≥ 30 min, injection mass (sample concentration × injection volume) < 1000 µL × mg-N/L for macromolecular proteins, and neutral pH mobile eluent. The dissolved O2 concentration in SEC mobile phase determined the upper limit of VUV oxidation at a specific oxidation time. Compared to conventional HW50S column (20 × 250 mm), HW40S column (20 × 350 mm) with mobile phase comprising of 1.5 g/L Na2HPO4·2H2O + 2.5 g/L KH2PO4 (pH = 6.85) could achieve a better separation of DON, nitrite, nitrate, and ammonia. When applied to river water, lake water, wastewater effluent, groundwater, and landfill leachate, the SEC-OND method could quantify DON as well as DIN species accurately and conveniently even the DIN/TDN ratio reached 0.98.

Unravelling relationships between fluorescence spectra, molecular weight distribution and hydrophobicity fraction of dissolved organic matter in municipal wastewater.

The characteristics of dissolved organic matter (DOM) in the influent and secondary effluent from 6 municipal wastewater treatment plants (WWTPs) were investigated with a size exclusion chromatogram (SEC) coupled with multiple detectors to simultaneously detect ultraviolet absorbance, fluorescence, dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) as a function of molecular weight (MW). The SEC chromatograms showed that biopolymers (>6 kDa) and humic substances (0.5-6 kDa) comprised the significant fraction in the influent, while humic substances became the abundant proportion in the secondary effluent. Direct linkages between MW distribution and hydrophobicity of DOM in the secondary effluent were further explored via SEC analysis of XAD resin fractions. DON and DOC with different hydrophobicity exhibited significantly distinct MW distribution, indicating that it was improper to consider DOC as a surrogate for DON. Different from DOC, the order of averaged MW in terms of DON was hydrophobic neutral ≈ transphilic neutral > hydrophobic acid > transphilic acid > hydrophilic fraction. Fluorescence spectral properties exhibited a significant semi-quantitative correlation with MW and hydrophobicity of DOC, with Pearson's coefficients of -0.834 and 0.754 (p < 0.01) for biopolymer and humic substances. Meanwhile, regional fluorescence proportion was demonstrated to indicate the MW and hydrophobicity properties of DON at the semi-quantitative level. The fluorescence excitation-emission matrix (EEM) could be explored to provide a rapid estimation of MW distribution and hydrophobic/hydrophilic proportion of DOC and DON in WWTPs.

Release and removal of algal organic matter during prechlorination and coagulation treatment of cyanobacteria-laden water: Are we on track?

A better understanding of the physicochemical properties and fate of algae-derived organic matter (AOM) in water treatments significantly benefits the control of algae-derived disinfection byprodcuts and process parameter optimization. In this study, we conducted a comprehensive investigation of the release and treatability of dissolved organic matter during prechlorination and postcoagulation treatments of cyanobacteria-laden source water via size-exclusion chromatography-tandem diode array detector, fluorescence detector and organic carbon detector. The results revealed that the allochthonous humic substances could protect algal cell membrane from damage during prechlorination at a low level of chlorine dose. Due to the release and oxidation of biopterins during prechlorination of M. aeruginosa cells, the variation of the humic-like fluorescence can be used to indicate the chlorine dose for a sufficient membrane damage of algae cells. The prechlorination of M. aeruginosa cells induced minimal release of large MW biopolymer fractions but much more release of low MW fractions E1 and E2 (i.e., unknown carbonaceous substances and fluorescent nitrogenous biopterins). The physically extracted AOM contained a large proportion of biopolymers and could not well represent those released during prechlorination treatment. During coagulation, the negative effect of humic substances on the coagulant demand to achieve algae removal was more remarkable than AOM released by prechlorination. The high-MW biopolymers and humic substances can be removed over 50% by coagulation. Among the low-MW carbonaceous fractions, E1 released by prechlorination can also be effectively removed via coagulation while fractions C, D (possibly oligopeptides or secondary aromatic metabolites & low MW acids) and nitrogenous biopterins were recalcitrant to coagulation. This study highlights the differences of AOM properties between physical extraction and prechlorination and provides a basis for drinking water treatment plants to give more attention to the recalcitrant low MW fractions in coagulation when treating algae-laden source water.

Elucidating the production and inhibition of melanoidins products on anaerobic digestion after thermal-alkaline pretreatment.

The refractory organics released from waste activated sludge (WAS) are unwanted produced in thermal-alkaline pretreatment, which are not well documented. In this study, we refer to them as melanoidins products (MPs) with characteristics of high molecular weight and inhibition to microbes. The results showed that these MPs from thermal-alkaline (80 °C and pH 10) pretreatment of WAS were identified with a broad molecular weight (>1000 Da). Dark-colored MPs were further verified from glucose and tryptophan as the model components, with values of UV280 and UV420 increasing. The produced MPs with a molecular weight of 1220, 6835, and even 21,200,000 Da were confirmed by SEC-HPLC. Unexpectedly, MPs were found to be electroactive with higher redox peak values than that of humic acids, which were almost not degraded by anaerobes as revealed by SEC-HPLC and 3D-EEM spectra. For the first time, the results demonstrated that MPs delayed volatile fatty acids production and reduced the methane yield (22-26% lower), which was likely attributed to the toxicity and/or electrons competition with anaerobes such as Methanosaeta. Thus, it is clear that MPs negatively impact anaerobic digestion after thermal-alkaline pretreatment, which shall be re-evaluated to minimize MPs when producing biochemicals from WAS.

NLRP4 negatively regulates type I interferon response and influences the outcome in anti-programmed cell death protein (PD)-1/PD-ligand 1 therapy.

The challenge to improve the clinical efficacy and enlarge the population that benefits from immune checkpoint inhibitors (ICIs) for non-small-cell lung cancer (NSCLC) is significant. Based on whole-exosome sequencing analysis of biopsies from NSCLC patients before anti-programmed cell death protein-2 (PD-1) treatment, we identified NLRP4 mutations in the responders with a longer progression-free survival (PFS). Knockdown of NLRP4 in mouse Lewis lung cancer cell line enhanced interferon (IFN)-α/ß production through the cGAS-STING-IRF3/IRF7 axis and promoted the accumulation of intratumoral CD8+ T cells, leading to tumor growth retardation in vivo and a synergistic effect with anti-PD-ligand 1 therapy. This was consistent with clinical observations that more tumor-infiltrating CD8+ T cells and elevated peripheral IFN-α before receiving nivolumab treatment were associated with a longer PFS in NSCLC patients. Our study highlights the roles of tumor-intrinsic NLRP4 in remodeling the immune contextures in the tumor microenvironment, making regional type I IFN beneficial for ICI treatment.

Controlling volatile fatty acids production from waste activated sludge by an alginate-degrading consortium.

It is desirable to control volatile fatty acids (VFAs) recovery from waste activated sludge (WAS) while avoiding the release of N and P. Structural extracellular polymeric substances (St-EPS), with typical components of alginate and polygalacturonic acid, resist the biodegradation of extracellular polymeric substances (EPS) in WAS. Previously, we purposely enriched an alginate-degrading consortium (ADC), but, both controlling VFAs production and cell integrity after dosing with ADC were not investigated. In this work, ADC with a high percentage of the genus Bacteroides (~67%) was further enriched with alginate utilization above 95%. The St-EPS content in WAS was 109.7 ± 3.3 mg/g-VSS, accounting for 31% of EPS. After dosing ADC in the WAS, the main metabolites were acetate (1.6 g/L) and propionate (0.7 g/L), the hydrolysis efficiency was increased to 38%, and the acidification efficiency was increased to 72%. Cell integrity was maintained during WAS fermentation by dosing with ADC according to no P release and unchanged lactate dehydrogenase activity. VFA production was mainly from the EPS, and protein degradation in EPS resulted in low N release (e.g., 212 mg/L from casein and no P release). Consequently, ADC doing offers the advantages of controlling VFAs production from EPS while maintaining cell integrity.

Developing a restricted chlorine-dosing strategy for UV/chlorine and post-chlorination under different pH and UV irradiation wavelength conditions.

UV/chlorine and chlorination processes have drawn great interests of water treatment utilities for oxidation and disinfection purposes. This work proposed a restricted chlorine-dosing strategy for UV/chlorine and post-chlorination under different pH and UV irradiation conditions by comprehensively assessing the oxidation of natural organic matter (NOM), formation of 9 haloacetic acids (HAA9) and bromate, and alteration of toxicity. During UV/chlorine with restricted chlorine doses, the oxidation of NOM chromophores (i.e., ΔUVA254) showed an apparent dependence on cumulative exposures of free available chlorine (CTFAC); Meanwhile, HAA9 formation was determined by CTFAC values and could be linearly correlated with ΔUVA254 irrespective of pH and UV irradiation wavelength. Irradiated by 254 nm LP-Hg lamp, the faster chlorine photolysis produced relatively higher steady-state concentrations of Cl• and HO• species but resulted in lower CTFAC. Reducing CTFAC values by operation parameters (pH, UV wavelength and irradiation fluence) could mitigate HAA9 formation during UV/chlorine at a specific chlorine dose. Additionally, high bromide concentration and acidic pH promoted more bromo-HAAs formation, and the presence of NOM significantly suppressed bromate formation. Analogous to ozonation, the UV/chlorine pre-oxidation could reduce the HAA9 formation potentials during post-chlorination at mildly alkaline pH. The photobacterium bioassay further demonstrated that although the UV/chlorine treatment might have increased the acute toxicity, the post-chlorination treatment could polish the acute toxicity to the level of chlorination alone. These results suggest that with the restricted chlorine-dosing strategy, the trade-off between oxidation/disinfection efficiency and DBPs formation can be controlled by monitoring CTFAC and ΔUVA254 values during UV/chlorine treatment.

Characterizing property and treatability of dissolved effluent organic matter using size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors.

In this study, size exclusion chromatography with an array of absorbance, fluorescence, organic nitrogen and organic carbon detectors was used for characterizing property and treatability of effluent organic matter (EfOM) from 12 wastewater treatment plants. According to their apparent molecular weight (AMW), EfOM fractions were assigned to biopolymers (>20 kDa), humic substances that comprise sub-fractions of humic-like acids (HA-I & HA-II, 2.3-7.0 kDa) and fulvic-like acids (FA, 1.5-2.3 kDa), building blocks (0.55-1.5 kDa) and low molecular weight neutral substances (<550 Da). The fractions of biopolymers and low molecular weight neutral substances didn't show humic-like fluorescence, while the fractions of HA-II, FA and building blocks usually had signatures of both humic-like and protein-like fluorescence. Humic substances generally contributed the largest proportion of dissolved organic carbon and nitrogen (DOC & DON) in effluents. Coagulation removed EfOM fractions following the order of biopolymers > HA subfraction > FA subfraction > building blocks, while little removal of protein-like fluorescence in HA-II and FA subfractions was detected. Anion exchange treatment could effectively reduce DOC and DON concentrations; the sequence of the treatment efficiency was humic substances > biopolymers > building blocks. Increasing O3 doses caused DOC and DON of EfOM to be gradually transformed from large AMW fractions into small AMW fractions, while chromophores and fluorophores in HA subfractions were relatively more refractory than those in the other fractions. Size exclusion chromatography with multiple detectors are suggested to be an informative technique for estimating treatability of EfOM by advanced wastewater treatment processes.

FGF2/FGFR1 regulates autophagy in FGFR1-amplified non-small cell lung cancer cells.

BACKGROUND: Autophagy is a conserved catabolic process to degrade cellular organelles. The role of autophagy in cancer development is complex. Amplification of fibroblast growth factor receptor 1 (FGFR1) is one of the most frequent targets in lung squamous cell carcinoma (SQCC). Whether fibroblast growth factor 2 (FGF2)/FGFR1 contributes to the regulation of autophagy remains elusive. METHODS: Autophagic activity was evaluated by immunoblotting for microtubule-associated protein 1 light chain 3 (LC3), formation of GFP-LC3 puncta, and monodansylcadaverine (MDC) staining. The effect of autophagy inhibition on cell survival was assessed by cell viability and apoptosis assays. RESULTS: We elucidated that FGFR1 activation suppressed autophagy. Pharmacological or genetic inhibition of FGFR1 by AZD4547 or FGFR1 short hairpin RNA (shRNA) induced autophagy in FGFR1-amplified non-small cell lung cancer (NSCLC) cells, H1581 and H520 cells. Mechanistic study revealed that the induction of autophagy by FGFR1 inhibition was mediated through inhibiting the ERK/MAPK pathway not by AKT pathway, accompanied by upregulation of beclin-1. Furthermore, activation of ERK/MAPK by transfection with a constitutively active MEK1 (caMEK1) construct or knockdown of beclin-1 by RNAi could attenuate autophagy induced by FGFR1 inhibition. Beclin-1 expression was inversely correlated with MEK1 phosphorylation. Inhibition of autophagy by beclin-1 silencing could enhance apoptosis after AZD4547 treatment in H1581 and H520 cells. High levels of LC3B mRNA was a marker of poor prognosis in NSCLC patients. CONCLUSIONS: Simultaneously inhibiting FGFR1 and autophagy could enhance cell death which should be further explored in vivo.