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.

Structure-dependent antimicrobial mechanism of quaternary ammonium resins and a novel synthesis of highly efficient antimicrobial resin.

The demand for powerful and multifunctional water-treatment materials and reagents is increasing, because we are facing worse raw water quality, various tolerant bacteria, and risky disinfection by-products (DBPs) in drinking water. Quaternary ammonium resins (QARs) are promising candidates for water disinfection and purification, but their limited bactericidal capacities are difficult to improve because of the lack of guidelines for enhancing antibacterial efficiency. Therefore, we first systematically studied the structure-dependent antimicrobial mechanism of QARs and found that the best resin skeleton is acrylic-type, the optimal bactericidal alkyl is hexyl or octyl, the most applicable sizes are 80-100 meshes, the best counter anion is iodide ion, and the optimum quaternization reagent is iodoalkane. Moreover, the antibacterial capacity was demonstrated to depend on surficial N+ groups, correlating with surficial N+ charge density (R2 of 0.98) but not with exchange capacity (R2 of 0.26), physical adsorption of resin skeleton, or electrostatic adsorption of N+ groups. Based on these principles, we synthesized a new resin, Ac-81, with a surficial antibacterial design, which simultaneously exhibited better antimicrobial efficiency (two orders of magnitude) as well as higher contaminant removal potential (61.92%) compared to the traditional Ac-8C antibacterial resin. Furthermore, the new resin showed remarkable broad-spectrum antibacterial effects against Gram-negative E. coli and P. aeruginosa and Gram-positive B. subtilis and S. aureus in simulated water and actual water. Simultaneously, water quality was significantly improved, with HCO3-, SO42-, TN, TP, and TOC reduced by 79-90%, >99%, 66-85%, >99%, and 22-26%, respectively. Ac-81 is characterized by facile reusability, high treatment capacity of 1500 bed volume, and good adaptability for treating actual water, providing a promising alternative for drinking-water disinfection and purification.

Surficial N+ charge density indicating antibacterial capacity of quaternary ammonium resins in water environment.

The antibacterial effects of quaternary ammonium resins (QARs) have been reported for decades, but there are few practical applications because of limited improvements in bactericidal capacity and the absence of an efficient antibacterial-indicating parameter. An in-situ determination method of surficial N+ groups for QARs, defined as surficial N+ charge density, was first established to merely quantify the exposed surficial quaternary ammonium groups (QAs). The mechanism of the new method depends on the tetraphenylboron sodium standard solution (TS), which is a colloidal solution with high steric hindrance, making it difficult to permeate into QARs and further react with the inner QAs. The results showed that the antibacterial efficacy of QARs correlates with the surficial N+ charge density with R2 > 0.95 (R2 of 0.97 for Escherichia coli, R2 of 0.96 for Staphylococcus aureus) but not with the strong-base group exchange capacity or zeta potential. Furthermore, the surficial N+ charge density was demonstrated efficient to indicate the antibacterial capacities against both gram-negative and gram-positive bacteria for commercial QARs, including acrylic, styrene and pyridine resin skeletons, especially for the QARs with similar skeletons and similar QAs. Based on the finding that the bactericidal groups merely involve the surficial QAs of QARs, this study proposes a new direction for improving the antibacterial capacity by enriching the surficial QAs and enhancing the bactericidal property of these surficial QAs, and provides a practicable synthesis with two-step quaternization.

Antimicrobial resins with quaternary ammonium salts as a supplement to combat the antibiotic resistome in drinking water treatment plants.

The increasing finding of pathogens and antibiotic resistance genes (ARGs) in drinking water has become one of the most challenging global health threats worldwide. However, conventional disinfection strategies in drinking water treatment plants (DWTPs) require further optimization in combating the antibiotic resistome. Here, we show that antimicrobial resins with quaternary ammonium salts (AMRs-QAS) exhibit great potentials in diminishing specific potential pathogens that relatively resist chlorine or UV disinfection in DWTPs, and comprehensive analyses using microscopy and fluorescence techniques revealed that the antimicrobial capacity of AMRs-QAS mainly proceed via the bacterial adsorption and cell membrane dissociation. Moreover, a total of 15 among 30 selected ARGs, as well as 4 selected potential pathogens including Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli and Staphylococcus aureus were all detected in the source water. Coupling the AMRs-QAS with 0.2 mg/L chlorine resulted in higher removal efficiencies than chlorination (2 mg/L) or UV disinfection (400 mJ cm-2) for all the detected pathogens and ARGs in drinking water and significantly decreased the relative abundances of Pseudomonas aeruginosa, Bacillus subtilis, Escherichia coli, as well as all the detected ARGs (p < 0.05). Co-occurrences of pathogens and ARGs were revealed by a correlation network and possibly accounts for the ARGs removal. This coupled disinfection strategy overcomes the limitations of individual disinfection methods, i.e. the enrichment of specific pathogens and ARGs among bacterial populations, and provides an alternative for minimizing health risks induced by the antibiotic resistome in DWTPs.

Effects of Vitamin B6 Deficiency on the Composition and Functional Potential of T Cell Populations.

The immune system is critical in preventing infection and cancer, and malnutrition can weaken different aspects of the immune system to undermine immunity. Previous studies suggested that vitamin B6 deficiency could decrease serum antibody production with concomitant increase in IL4 expression. However, evidence on whether vitamin B6 deficiency would impair immune cell differentiation, cytokines secretion, and signal molecule expression involved in JAK/STAT signaling pathway to regulate immune response remains largely unknown. The aim of this study is to investigate the effects of vitamin B6 deficiency on the immune system through analysis of T lymphocyte differentiation, IL-2, IL-4, and INF-γ secretion, and SOCS-1 and T-bet gene transcription. We generated a vitamin B6-deficient mouse model via vitamin B6-depletion diet. The results showed that vitamin B6 deficiency retards growth, inhibits lymphocyte proliferation, and interferes with its differentiation. After ConA stimulation, vitamin B6 deficiency led to decrease in IL-2 and increase in IL-4 but had no influence on IFN-γ. Real-time PCR analysis showed that vitamin B6 deficiency downregulated T-bet and upregulated SOCS-1 transcription. This study suggested that vitamin B6 deficiency influenced the immunity in organisms. Meanwhile, the appropriate supplement of vitamin B6 could benefit immunity of the organism.

Supplemental Upward Lighting from Underneath to Obtain Higher Marketable Lettuce (Lactuca sativa) Leaf Fresh Weight by Retarding Senescence of Outer Leaves.

Recently, the so-called "plant factory with artificial lighting" (PFAL) approach has been developed to provide safe and steady food production. Although PFALs can produce high-yielding and high-quality plants, the high plant density in these systems accelerates leaf senescence in the bottom (or outer) leaves owing to shading by the upper (or inner) leaves and by neighboring plants. This decreases yield and increases labor costs for trimming. Thus, the establishment of cultivation methods to retard senescence of outer leaves is an important research goal to improve PFAL yield and profitability. In the present study, we developed an LED lighting apparatus that would optimize light conditions for PFAL cultivation of a leafy vegetable. Lettuce (Lactuca sativa L.) was hydroponically grown under white, red, or blue LEDs, with light provided from above (downward), with or without supplemental upward lighting from underneath the plant. White LEDs proved more appropriate for lettuce growth than red or blue LEDs, and the supplemental lighting retarded the senescence of outer leaves and decreased waste (i.e., dead or low-quality senescent leaves), leading to an improvement of the marketable leaf fresh weight.

Characterization of phytochemicals and antioxidant activities of red radish brines during lactic acid fermentation.

Red radish (Raphanus L.) pickles are popular appetizers or spices in Asian-style cuisine. However, tons of radish brines are generated as wastes from industrial radish pickle production. In this study, we evaluated the dynamic changes in colour properties, phenolics, anthocyanin profiles, phenolic acid composition, flavonoids, and antioxidant properties in radish brines during lactic acid fermentation. The results showed that five flavonoids detected were four anthocyanins and one kaempferol derivative, including pelargonidin-3-digluoside-5-glucoside derivatives acylated with p-coumaric acid, ferulic acid, p-coumaric and manolic acids, or ferulic and malonic acids. Amounts ranged from 15.5-19.3 µg/mL in total monomeric anthocyanins, and kaempferol-3,7-diglycoside (15-30 µg/mL). 4-Hydroxy-benzoic, gentisic, vanillic, syringic, p-coumaric, ferulic, sinapic and salicylic acids were detected in amounts that varied from 70.2-92.2 µg/mL, whereas the total phenolic content was 206-220 µg/mL. The change in colour of the brine was associated with the accumulation of lactic acid and anthocyanins. The ORAC and Fe2+ chelation capacity of radish brines generally decreased, whereas the reducing power measured as FRAP values was increased during the fermentation from day 5 to day 14. This study provided information on the phytochemicals and the antioxidative activities of red radish fermentation waste that might lead to further utilization as nutraceuticals or natural colorants.

VPPIPP and IPPVPP: two hexapeptides innovated to exert antihypertensive activity.

In this study, two hexapeptides of IPPVPP and VPPIPP were innovated by using two commercial antihypertensive peptides IPP and VPP as two domains cis-linked and trans-linked, respectively. The IPPVPP and VPPIPP were chemically synthesized and evaluated for the antihypertensive activity in vitro/vivo. The in vitro ACE-inhibitory study showed that VPPIPP (34.71 ± 4.38%) has a significantly stronger activity than that of IPPVPP (13.17 ± 0.25%) at a treatment concentration of 10 µmol/L, but it was weaker than the commercial IPP (56.97 ± 2.40%) (P<0.05). However, VPPIPP, IPPVPP, and IPP lowered the systolic blood pressure by 21 ± 0.9%, 17.4 ± 1.3% and 17.5 ± 0.9%, respectively, in rats at 1.5 mg/kg body weight dosage. The result was consistent with the mRNA level of sarcoplasmic reticulum Ca(2+), Mg(2+) -ATPase Gene (SERCA 2a) in rat hearts. Additionally, VPPIPP and IPPVPP showed no negative impact on blood glycometabolism. The results suggested that the two hexapeptides could be potent bioactive peptides in functional foods for people with high blood pressure.