Catalysis of Alloys: Classification, Principles, and Design for a Variety of Materials and Reactions.

Alloying has long been used as a promising methodology to improve the catalytic performance of metallic materials. In recent years, the field of alloy catalysis has made remarkable progress with the emergence of a variety of novel alloy materials and their functions. Therefore, a comprehensive disciplinary framework for catalytic chemistry of alloys that provides a cross-sectional understanding of the broad research field is in high demand. In this review, we provide a comprehensive classification of various alloy materials based on metallurgy, thermodynamics, and inorganic chemistry and summarize the roles of alloying in catalysis and its principles with a brief introduction of the historical background of this research field. Furthermore, we explain how each type of alloy can be used as a catalyst material and how to design a functional catalyst for the target reaction by introducing representative case studies. This review includes two approaches, namely, from materials and reactions, to provide a better understanding of the catalytic chemistry of alloys. Our review offers a perspective on this research field and can be used encyclopedically according to the readers' individual interests.

ACRE, a class of AP2/ERF transcription factors, activates the expression of sweet potato ß-amylase and sporamin genes through the sugar-responsible element CMSRE-1.

Sugars, synthesized by photosynthesis in source organs, are loaded and utilized as an energy source and carbon skeleton in sink organs, and also known to be important signal molecules regulating gene expression in higher plants. The expression of genes coding for sporamin and ß-amylase, the two most abundant proteins in storage roots of sweet potato, is coordinately induced by sugars. We previously reported on the identification of the carbohydrate metabolic signal-responsible element-1 (CMSRE-1) essential for the sugar-responsible expression of two genes. However, transcription factors that bind to this sequence have not been identified. In this study, we performed yeast one-hybrid screening using the sugar-responsible minimal promoter region of the ß-amylase gene as bait and a library composed only transcription factor cDNAs of Arabidopsis. Two clones, named Activator protein binding to CMSRE-1 (ACRE), encoding AP2/ERF transcription factors were isolated. ACRE showed transactivation activity of the sugar-responsible minimal promoter in a CMSRE-1-dependent manner in Arabidopsis protoplasts. Electric mobility shift assay (EMSA) using recombinant proteins and transient co-expression assay in Arabidopsis protoplasts revealed that ACRE could actually act to the CMSRE-1. Among the DEHYDRATION -RESPONSIVE ELEMENT BINDING FACTOR (DREB) subfamily, almost all homologs including ACRE, could act on the DRE, while only three ACREs could act to the CMSRE-1. Moreover, ACRE-homologs of Japanese morning glory also have the same property of DNA-binding preference and transactivation activity through the CMSRE-1. These findings suggested that ACRE plays an important role in the mechanism regulating the sugar-responsible gene expression through the CMSRE-1 conserved across plant species.

Physicochemical parameters affecting the adhesion of ciprofloxacin-resistant Escherichia coli to activated sludge.

To investigate the physicochemical conditions necessary to stably remove antibiotic-resistant bacteria (ARB) via contact with activated sludge (AS), the adhesion of ciprofloxacin (CIP)-resistant and -susceptible Escherichia coli to AS was simulated by contact tests in the laboratory. The CIP-resistant E. coli and susceptible E. coli were removed by a 3 log smaller concentration by a 5 h contact test at maximum. Considering the hydraulic retention time of a reaction tank (∼5 h) and step-feeding operation, we considered the removal rate of E. coli in the current simulated contact test to be in agreement with the actual situation where 1-2 log concentrations of E. coli were reported to be removed from an AS reaction tank. With the increase in the AS concentration and/or dissolved oxygen, the removal rate of E. coli increased. The removal rate of CIP-resistant E. coli was greater than that of susceptible E. coli under all experimental conditions. Although the mechanism by which CIP-resistant E. coli preferably adhered to AS was not clearly understood in detail, finding optimum conditions under which bacteria, including ARB, were efficiently removed by the AS process may be possible.

Interstitial Carbon Dopant in Palladium-Gold Alloy Boosting the Catalytic Performance in Vinyl Acetate Monomer Synthesis.

Vinyl acetate monomer (VAM), an important chemical intermediate in industry, is produced by the well-established commercial process of acetoxylation of ethylene with Pd-Au/SiO2 and a KOAc promoter. No paper has since decades defined the true effects of Au and KOAc, despite numerous attempts to clarify them. The role of subsurface carbon as a catalyst booster for enhanced catalytic performance in VAM synthesis was found by us for the first time. X-ray diffraction and X-ray absorption fine structure studies revealed that carbon atoms spontaneously doped into the Pd-Au alloy lattice while maintaining the alloy's size, metallic state, and alloy composition. Additionally, during the process, the KOAc addition dramatically raised the equilibrium carbide fraction. Because of the high carbide fraction, KOAc/Pd0.8Au0.2/SiO2 had a 5.6-fold higher formation rate (89.0% selectivity) than Pd0.8Au0.2/SiO2 (69.2% selectivity) due to high carbide fraction. Surprisingly, kinetic and theoretical analyses showed that the coupling of acetate and ethylene, which is a rate-determining step, is effectively promoted by the synergistic contributions of Au (electronic/geometric effects) and interstitial carbon (electronic effect). Additionally, the synergy inhibits ethylene dehydrogenation, which ultimately slows the formation of CO2. The contentious debates about the roles of Au and KOAc in the acetoxylation of ethylene have been resolved thanks to experimental and theoretical insights into the roles of Pd-Au formation, Au/Pd ratio, and interstitial carbon atoms. These insights also open the door for the logical design of catalysts with desirable catalytic performance.

Surface Engineering of Titania Boosts Electroassisted Propane Dehydrogenation at Low Temperature.

Electric field catalysis using surface proton conduction, in which proton hopping and collision on the reactant are promoted by external electricity, is a promising approach to break the thermodynamic equilibrium limitation in endothermic propane dehydrogenation (PDH). This study proposes a catalyst design concept for more efficient electroassisted PDH at low temperature. Sm was doped into the anatase TiO2 surface to increase surface proton density by charge compensation. Pt-In alloy was deposited on the Sm-doped TiO2 for more favorable proton collision and selective propylene formation. The catalytic activity in electroassisted PDH drastically increased by doping an appropriate amount of Sm (1 mol % to Ti) where the highest propylene yield of 19.3 % was obtained at 300 °C where the thermodynamic equilibrium yield was only 0.5 %. Results show that surface proton enrichment boosts alkane dehydrogenation at low temperature.

High-Entropy Intermetallics Serve Ultrastable Single-Atom Pt for Propane Dehydrogenation.

Propane dehydrogenation has been a promising propylene production process that can compensate for the increasing global demand for propylene. However, Pt-based catalysts with high stability at ≥600 °C have barely been reported because the catalysts typically result in short catalyst life owing to side reactions and coke formation. Herein, we report a new class of heterogeneous catalysts using high-entropy intermetallics (HEIs). Pt-Pt ensembles, which cause side reactions, are entirely diluted by the component inert metals in PtGe-type HEIs. The resultant HEI (PtCoCu) (GeGaSn)/Ca-SiO2 exhibited an outstandingly high catalytic stability, even at 600 °C (kd-1 = τ = 4146 h = 173 d), and almost no deactivation of the catalyst was observed for 2 months for the first time. Detailed experimental studies and theoretical calculations demonstrated that the combination of the site-isolation and entropy effects upon multi-metallization of PtGe drastically enhanced the desorption of propylene and the thermal stability, eventually suppressing the side reactions even at high reaction temperatures.

Investigation on the applicability of a long-range reverse-transcription quantitative polymerase chain reaction assay for the rapid detection of active viruses.

BACKGROUND: Although conventional polymerase chain reaction (PCR) methods are widely used in diagnosis, the titer of the pathogenic virus is difficult to determine based on the PCR. In our prior report, a long-range reverse-transcription quantitative PCR (LR-RT-qPCR) assay was developed to assess the titer of UV-irradiated influenza A virus (IAV) rapidly. In this research, we focused on whether the LR-RT-qPCR assay could evaluate the titer of IAV inactivated by other methods. METHODS: IAV was inactivated by: heating at 100 °C for periods ranging from 1 to 15 min, treating with 0.12% sodium hypochlorite for periods ranging from 3 to 30 min, or treating with 70% ethanol for periods ranging from 10 to 30 min. Fifty percent tissue culture infectious dose (TCID50) assay was performed to confirm the efficacy of the inactivation methods, followed by LR-RT-qPCR to investigate the correlation between infectivity and copy number. RESULTS: One minute heating, 3 min sodium hypochlorite treatment, or 10 min ethanol treatment was sufficient to deactivate IAV. Changes before and after the inactivations in the copy numbers on LR-RT-qPCR were significantly different among the inactivation methods. Heat-inactivation drastically decreased the copy number to below the cutoff value around 5 copies/µL after 5 min treatment. The inactivation time of heating estimated using LR-RT-qPCR was marginally higher than that determined using TCID50. However, the treatments with sodium hypochlorite or ethanol moderately and minimally affected the copy numbers obtained using LR-RT-qPCR (~ 1 digit or no copy number decrease), respectively. CONCLUSIONS: In addition to good applicability in UV-irradiation previously reported, the LR-RT-qPCR method is suitable for evaluating the effect of heat-inactivation on IAV infectivity. However, minor modifications may be made and investigated in the future to reduce the time intervals with TCID50. Although this method is not applicable for the ethanol inactivation, rapid evaluation of the effects of chlorination on IAV can be determined by comparing copy numbers before and after treatment using the LR-RT-qPCR method.

Nickel-Based High-Entropy Intermetallic as a Highly Active and Selective Catalyst for Acetylene Semihydrogenation.

Acetylene semihydrogenation is a key technology for producing polymer-grade ethylene from crude ethylene. Ni-based catalysts are promising alternatives to noble-metals for this process. However, achieving high catalytic activity and selectivity remains a big challenge. We report a novel catalyst design based on high-entropy intermetallics (HEI), which provide thermally stable isolated Ni without excess counterpart metals and achieve exceptionally high performance. Intermetallic NiGa was multi-metalized to a (NiFeCu)(GaGe), where the Ni and Ga sites were partially substituted with Fe/Cu and Ge, respectively, without altering the parent CsCl-type structure. The NiFeCuGaGe/SiO2 HEI catalyst completely inhibited ethylene overhydrogenation even at complete acetylene conversion, and exhibited five-times higher activity than other 3d-transition-metal-based catalysts. The DFT study showed that the surface energy decreased by multi-metallization, which drastically weakened ethylene adsorption.

Doubly Decorated Platinum-Gallium Intermetallics as Stable Catalysts for Propane Dehydrogenation.

Propane dehydrogenation (PDH) is a promising chemical process that can satisfy the increasing global demand for propylene. However, the Pt-based catalysts that have been reported thus far are typically deactivated at ≥600 °C by side reactions and coke formation. Thus, such catalysts possess an insufficient life. Herein, we report a novel catalyst design concept, namely, the double decoration of PtGa intermetallics by Pb and Ca, which synergize the geometric and electronic promotion effects on the catalyst stability, respectively. Pb is deposited on the three-fold Pt3 sites of the PtGa nanoparticles to block them, whereas Ca, which affords an electron-enriched single-atom-like Pt1 site, is placed around the nanoparticles. Thus, PtGa-Ca-Pb/SiO2 exhibits an outstandingly high catalytic stability, even at 600 °C (kd =0.00033 h-1 , τ=3067 h), and almost no deactivation of the catalyst was observed for up to 1 month for the first time.

Quick assessment of influenza a virus infectivity with a long-range reverse-transcription quantitative polymerase chain reaction assay.

BACKGROUND: The polymerase chain reaction (PCR) is commonly used to detect viral pathogens because of its high sensitivity and specificity. However, conventional PCR methods cannot determine virus infectivity. Virus infectivity is conventionally examined with methods such as the plaque assay, even though such assays require several days. Long-range reverse-transcription quantitative PCR (RT-qPCR) has previously been suggested for the rapid assessment of RNA virus infectivity where the loss of infectivity is attributable to genomic fragmentation. METHODS: IAV was irradiated with 253.7 nm ultraviolet (UV) rays to induce genomic strand breaks that were confirmed by a full-length RT-PCR assay. The IAV was then subjected to plaque assay, conventional RT-qPCR and long-range RT-qPCR to examine the relationship between infectious titer and copy number. A simple linear regression analysis was performed to examine the correlation between the results of these assays. RESULTS: A long-range RT-qPCR assay was developed and validated for influenza A virus (IAV). Although only a few minutes of UV irradiation was required to completely inactivate IAV, genomic RNA remained detectable by the conventional RT-qPCR and the full-length RT-PCR for NS of viral genome following inactivation. A long-range RT-qPCR assay was then designed using RT-priming at the 3' termini of each genomic segment and subsequent qPCR of the 5' regions. UV-mediated IAV inactivation was successfully analyzed by the long-range RT-qPCR assay especially when targeting PA of the viral genome. This was also supported by the regression analysis that the long-range RT-qPCR is highly correlated with plaque assay (Adjusted R2 = 0.931, P = 0.000066). CONCLUSIONS: This study suggests that IAV infectivity can be predicted without the infectivity assays. The rapid detection of pathogenic IAV has, therefore, been achieved with this sensing technology.

In Vivo Examination of Mouse APOBEC3- and Human APOBEC3A- and APOBEC3G-Mediated Restriction of Parvovirus and Herpesvirus Infection in Mouse Models.

UNLABELLED: APOBEC3 knockout and human APOBEC3A and -3G transgenic mice were tested for their ability to be infected by the herpesviruses herpes simplex virus 1 and murine herpesvirus 68 and the parvovirus minute virus of mice (MVM). Knockout, APOBEC3A and APOBEC3G transgenic, and wild-type mice were equally infected by the herpesviruses, while APOBEC3A but not mouse APOBEC3 conferred resistance to MVM. No viruses showed evidence of cytidine deamination by mouse or human APOBEC3s. These data suggest that in vitro studies implicating APOBEC3 proteins in virus resistance may not reflect their role in vivo IMPORTANCE: It is well established that APOBEC3 proteins in different species are a critical component of the host antiretroviral defense. Whether these proteins also function to inhibit other viruses is not clear. There have been a number of in vitro studies suggesting that different APOBEC3 proteins restrict herpesviruses and parvoviruses, among others, but whether they also work in vivo has not been demonstrated. Our studies looking at the role of mouse and human APOBEC3 proteins in transgenic and knockout mouse models of viral infection suggest that these restriction factors are not broadly antiviral and demonstrate the importance of testing their activity in vivo.

Dysfunction of bovine endogenous retrovirus K2 envelope glycoprotein is related to unsuccessful intracellular trafficking.

UNLABELLED: Endogenous retroviruses (ERVs) are the remnants of retroviral infection of ancestral germ cells. Mutations introduced into ERVs halt the production of infectious agents, but their effects on the function of retroviral proteins are not fully understood. Retroviral envelope glycoproteins (Envs) are utilized in membrane fusion during viral entry, and we recently identified intact coding sequences for bovine endogenous retrovirus K1 (BERV-K1) and BERV-K2 Envs. Amino acid sequences of BERV-K1 Env (also called Fematrin-1) and BERV-K2 Env are similar, and both viruses are classified in the genus Betaretrovirus. While Fematrin-1 plays an important role in cell-to-cell fusion in bovine placenta, the BERV-K2 envelope gene is marginally expressed in vivo, and its recombinant Env protein is defective in membrane fusion due to inefficient cleavage of surface (SU) and transmembrane subunits. Here, we conducted chimeric analyses of Fematrin-1 and BERV-K2 Envs and revealed that defective maturation of BERV-K2 Env contributed to failed intracellular trafficking. Fluorescence microscopy and flow cytometric analysis suggested that in contrast to Fematrin-1 Env, BERV-K2 Env could not be transported from the endoplasmic reticulum to the trans-Golgi network, where cellular proteases required for processing retroviral Envs are localized. We also identified that one of the responsive regions of this phenomenon resided within a 65-amino-acid region of BERV-K2 SU. This is the first report to identify that retroviral Env SU is involved in the regulation of intracellular trafficking, and it may help to elucidate the maturation process of Fematrin-1 and other related Envs. IMPORTANCE: Retroviruses utilize envelope glycoproteins (Envs) to enter host target cells. Mature retroviral Env is a heterodimer, which consists of surface (SU) and transmembrane (TM) subunits that are generated by the cleavage of an Env precursor protein in the trans-Golgi network. SU and TM mediate the recognition of the entry receptor and virus-host membrane fusion, respectively. However, unexplained issues remain for the maturation process of retroviral Env. We previously reported that bovine endogenous retrovirus K2 (BERV-K2) Env lost fusogenicity due to a defect in the cleavage of SU and TM. In this study, we identified that mutations residing in BERV-K2 SU disturbed intracellular trafficking of BERV-K2 Env and resulted its inefficient cleavage. Because SU is not known to play an important role in this process, our study may provide novel insights into the maturation mechanism of retroviral Envs.

Fematrin-1 is involved in fetomaternal cell-to-cell fusion in Bovinae placenta and has contributed to diversity of ruminant placentation.

During placentation, mammals employ different strategies for nourishing and supporting fetuses. Members of the Bovidae family, consisting of cloven-hoofed ruminants, utilize multiple maternal attachment points on the placenta, known as cotyledons, and hybrid cells, named trinucleate cells or syncytial plaques, made up of a fusion of fetal trophoblasts and maternal endometrial cells to provide essential hormones and maintain long gestation periods. These hybrid cells are unique to the Bovidae, as fetomaternal borders are clearly separated by syncytiotrophoblasts or epithelial cells in the placenta of other mammals. Recently, it was reported that Syncytin-Rum1 was inserted into ruminant genomes, including cattle and sheep, and was possibly involved in fetomaternal cell-to-cell fusion in both species. However, Syncytin-Rum1 alone is insufficient to explain the morphological diversity of the fetomaternal hybrids between Bovinae and Caprinae (i.e., trinucleate cells in Bovinae and syncytial plaques in Caprinae). Here we report that the bovine endogenous retrovirus K1 (BERV-K1) envelope, which we term Fematrin-1, was specifically expressed in binucleated trophoblasts throughout gestation in cattle and induced fusion with bovine endometrial cells in vitro at a significantly higher level than Syncytin-Rum1 under physiological conditions. Fematrin-1 was found to be integrated into intron 18 of FAT tumor suppressor homolog 2 (FAT2) about 18.3 to 25.4 million years ago and has been subject to purifying selection through the evolution of Bovinae. Phylogenetically, Fematrin-1 is distinct from Syncytin genes found in other mammalian species that form syncytiotrophoblasts. Our results suggest that the newly acquired endogenous retroelement has contributed to generating placentation diversity through ruminant evolution.

Solid-phase fluorescence: Reproducibility and comparison with the solution states.

Solid-phase fluorescence excitation-emission matrix (SPF-EEM) spectroscopy has potential for non-extractive, non-destructive, and non-contact analytical measurements of powder and solid-state samples, as well as front-face EEM spectroscopy for suspensions of high optical density. However, as there is no unified measurement method for SPF spectroscopy, comparing samples measured in different research fields is difficult. Therefore, this study designs a cell that can be created by a 3D printer and examines reproducibility on measuring fluorescent powders. The developed cell is applied to proteins (ovalbumin, BSA, gliadin, gluten, powdered collagen, casein), amino acids (tryptophan, tyrosine, and phenylalanine), soybean ingredients (daidzein, and genistein), and fluorescent chemicals (rhodamine B, fluorescein sodium salt, pyrene, and quinine sulfate dihydrate) and their spectra are compared with those in the solution states. When samples are refilled into the cell three times, the cell exhibits high reproducibility in terms of fluorescence peak wavelength and intensity. The solid proteins exhibit peaks attributed to the fluorescent amino acid residues, and broad peaks which are not detected for the proteins in the solution states. Powdered rhodamine B and fluorescein sodium salt do not exhibit fluorescence, possibly due to the inner-filter effect (IFE). Some non-colored molecules also exhibit loss of fluorescence or a remarkable difference between the solid and solution states, possibly due to the interaction of the fluorescent structure with the surrounding local environment, similar to the solvent effect, which is possibly affected by the molecular proximity, three-dimensional structure, and moisture absorption capacity.

Development of an internal two-stage upflow anaerobic reactor integrating biostimulation strategies to enhance the degradation of aromatic compounds in wastewater from purified terephthalic acid and dimethyl terephthalate manufacturing processes.

In this study, we aimed to establish high-rate biological treatment of purified terephthalic acid (PTA) and dimethyl terephthalate (DMT) wastewater that minimizes the inhibitory effects of high concentration benzoate and acetate. To achieve this, we developed a novel bioreactor system and biostimulation strategy. An internal two-stage upflow anaerobic (ITUA) reactor was operated with (i) a packed bed containing green tuff medium underlying (ii) a compartment seeded with anaerobic granular sludge. Ethylene glycol was amended to stimulate syntrophic interactions. Continuous operation of the system for 1,026 days achieve an organic removal rate of 11.0 ± 0.6 kg COD/m3/d. The abundance of aromatic degraders significantly increased during operation. Thus, we successfully developed a high-rate treatment system to treat wastewater from the PTA/DMT manufacturing processes by activating syntrophs in an ITUA reactor.

Nucleos(t)ide analogs for hepatitis B virus infection differentially regulate the growth factor signaling in hepatocytes.

BACKGROUND: Recent clinical studies have suggested that the risk of developing HCC might be lower in patients with chronic hepatitis B receiving tenofovir disoproxil fumarate than in patients receiving entecavir, although there is no difference in biochemical and virological remission between the 2 drugs. METHODS: The effects of nucleoside analogs (NsAs; lamivudine and entecavir) or nucleotide analogs (NtAs; adefovir disoproxil, tenofovir disoproxil fumarate, and tenofovir alafenamide) on cell growth and the expression of growth signaling molecules in hepatoma cell lines and PXB cells were investigated in vitro. The tumor inhibitory effects of NsAs or NtAs were evaluated using a mouse xenograft model, and protein phosphorylation profiles were investigated. The binding of NsAs or NtAs to the insulin receptor (INSR) was investigated by thermal shift assays. RESULTS: NtAs, but not NsAs, showed direct growth inhibitory effects on hepatoma cell lines in vitro and a mouse model in vivo. A phosphoprotein array revealed that INSR signaling was impaired and the levels of phosphorylated (p)-INSRß and downstream molecules phosphorylated (p)-IRS1, p-AKT, p-Gab1, and p-SHP2 were substantially reduced by NtAs. In addition, p-epidermal growth factor receptor and p-AKT levels were substantially reduced by NtAs. Similar findings were also found in PXB cells and nontumor lesions of liver tissues from patients with chronic hepatitis B. Prodrug NtAs, but not their metabolites (adefovir, adefovir monophosphate, adefovir diphosphate, tenofovir, tenofovir monophosphate, and tenofovir diphosphate), had such effects. A thermal shift assay showed the binding of NtAs to INSRß. CONCLUSIONS: NtAs (adefovir disoproxil, tenofovir disoproxil fumarate, and tenofovir alafenamide), which are adenine derivative acyclic nucleotide analogs, potentially bind to the ATP-binding site of growth factor receptors and inhibit their autophosphorylation, which might reduce the risk of HCC in patients with chronic hepatitis B.

Tracing morphological characteristics of activated sludge flocs by using a digital microscope and their effects on sludge dewatering and settling.

ABSTRACTIn wastewater treatment by the activated sludge (AS) process, settleability and dewaterability of AS are key issues that are directly related to the treated water quality and sludge treatment costs. Several studies investigated the relationship between the shape of AS flocs and their settling/dewatering property. To quantify the floc morphology, it is imperative to attach a camera to a microscope or move the stage manually. Hence, labour and equipment costs may increase. In this study, by combining a digital microscope and an automatic stage, more than 100 magnified floc images were rapidly obtained from one AS sample dropped on a slide glass, and shape parameters were collectively calculated using an analysis software. During 1-year monitoring of four wastewater treatment plants in Sapporo City (Hokkaido, Japan), the morphological parameters and extracellular polymeric substances (EPS) quantity/quality of AS were analyzed on the basis of their correlation to the time to filtration (TTF) and sludge volume index (SVI), which are indicators for describing the dewatering and settling properties of AS, respectively. In one plant, larger, denser, and smoother flocs tended to contain less EPS and exhibited better sludge dewaterability. In another plant, larger, denser, and smoother flocs were considered to contribute to better settlement. Especially, an equivalent high-density floc diameter and the ratio of mixed liquor suspended solids (MLSS) concentration to the total floc area were commonly suggested to explain AS dewaterability and settleability.

Quantification of organic fluorophores in absorbing media by solid-phase fluorescence excitation-emission matrix (SPF-EEM) spectroscopy of modeled mixtures containing bovine serum albumin (BSA) and colorants.

Solid-phase fluorescence excitation-emission matrix (SPF-EEM) spectroscopy is beneficial for investigating the characteristics of natural organic matter (NOM) in the solid phase without extraction procedures. However, inner filter effect (IFE) due to the presence of dark components in samples can make it difficult to quantify the fluorophore concentration. To establish a new method to determine unknown concentrations of a fluorescent material in a sample containing various absorbing materials by SPF spectroscopy, modeled mixtures containing bovine serum albumin (BSA) and colorants at different ratios were examined. Fluorescence intensities of BSA against various concentrations afforded different saturation curves for different colorants in the mixtures, suggesting that it is difficult to use the SPF intensity for quantifying the concentration of fluorescent samples in which IFE has occurred, because one cannot obtain a single calibration curve that does not depend on the absorbing medium that it is mixed in. However, products of the fluorescence intensity and Kubelka-Munk (KM) function at the excitation wavelength were proportional to the first order of BSA weight concentrations, regardless of the colorant type. By using this trend as a calibration curve, it may be possible to quantify the amount of BSA from its SPF-EEM spectrum. In this study, the KM function was obtained using an ultraviolet-visible (UV-Vis) spectrometer with an integrating sphere. To reduce the labor and equipment cost of UV-Vis spectroscopy, a substrate of the KM function also was obtained from the Rayleigh scattering in an SPF-EEM spectrum, which could be used as a parameter for calibration curves that quantify the BSA concentration. Although further studies are required, this study proposed that the product of the SPF intensity and KM function at the excitation wavelength can be partially used for an empirical formula to quantify a variety of fluorescent materials mechanically mixed with various absorbing materials.

Growth of the Nitrosomonas europaea cells in the biofilm and planktonic growth mode: Responses of extracellular polymeric substances production and transcriptome.

Nitrosomonas europaea, an aerobic ammonia oxidizing bacterium, is responsible for the first and rate-limiting step of the nitrification process, and their ammonia oxidation activities are critical for the biogeochemical cycling and the biological nitrogen removal of wastewater treatment. In the present study, N. europaea cells were cultivated in the inorganic or organic media (the NBRC829 and the nutrient-rich, NR, media, respectively), and the cells proliferated in the form of planktonic and biofilm in those media, respectively. The N. europaea cells in the biofilm growth mode produced larger amounts of the extracellular polymeric substances (EPS), and the composition of the EPS was characterized by the chemical analyses including Fourier transform infrared spectroscopy (FT-IR) and 1H-nuclear magnetic resonance (NMR) measurements. The RNA-Seq analysis of N. europaea in the biofilm or planktonic growth mode revealed that the following gene transcripts involved in central nitrogen metabolisms were abundant in the biofilm growth mode; amo encoding ammonia monooxygenase, hao encoding hydroxylamine dehydrogenase, the gene encoding nitrosocyanine, nirK encoding copper-containing nitrite reductase. Additionally, the transcripts of the pepA and wza involved in the bacterial floc formation and the translocation of EPS, respectively, were also abundant in the biofilm-growth mode. Our study was first to characterize the EPS production and transcriptome of N. europaea in the biofilm and planktonic growth mode.

A simple and rapid method for detecting fecal pollution in urban rivers by measuring the intrinsic ß-D-glucuronidase activity of Escherichia coli.

As urban rivers are domestic, industrial, and agricultural water resources, fecal pollution poses human health and environmental risks. In this study, we developed a simple and rapid method to detect fecal pollution in urban rivers. Water samples were mixed with liquid medium, including a fluorescent substrate and fluorescence intensity (F.I.) was measured using a microplate reader to determine Escherichia coli (E. coli) ß-D-glucuronidase (GUS) activity instead of E. coli concentration. GUS activities measurements in pure E. coli cultures revealed that E. coli incubated with a GUS substrate accumulated GUS enzymes in their cells, whereas those incubated without a GUS substrate did not. The increase in GUS activity corresponded to the proliferation of E. coli and the GUS activity increased linearly even during the lag growth phase of E. coli, indicating the presence of intrinsic GUS (iGUS) in E. coli cells before incubation. iGUS activity persisted at 81 % in the chlorinated samples, even though the E. coli concentration was reduced by a factor of 106. The iGUS activity persisted for approximately three days. Therefore, we assumed that E. coli present in fecal contaminants, in which GUS substrates are present, could be distinguished from those surviving in the natural environment for three days or longer by measuring iGUS activity. River water samples were collected upstream and downstream of the discharge outlets of municipal wastewater treatment plants and a combined sewer outlet. The iGUS activities were <0.24 mMFU/mL for the upstream samples and >0.21 mMFU/mL for the downstream samples. Interestingly, E. coli concentrations were not necessarily associated with fecal pollution. This indicates that by setting a threshold for iGUS activity, our method can be used as a simple and rapid method for detecting fecal pollution in urban rivers. Because the limit of detection for our method is 20 CFU/mL, our method is applicable to detecting high fecal pollution in a small river.