Second-order advantage achieved by unfolded-partial least-squares/residual bilinearization modeling of excitation-emission fluorescence data presenting inner filter effects

A second-order multivariate calibration approach, based on a combination of unfolded-partial least-squares with residual bilinearization (U-PLS/RBL), has been applied to fluorescence excitation-emission matrix data for multicomponent mixtures showing inner filter effects. The employed chemometric algorithm is the most successful one regarding the prediction of analyte concentrations when significant inner filter effects occur, even in the presence of unexpected sample components, which require strict adherence to the second-order advantage. Results for simulated fluorescence excitation-emission data are described, in comparison with the classical approach based on parallel factor analysis and other second-order algorithms, including generalized rank annihilation, bilinear least squares combined with residual bilinearization and multivariate curve resolution-alternating leastsquares. A set of experimental data was also studied, in which calibration was performed with fluorescence excitation-emission matrices for samples containing mixtures of chrysene (the analyte of interest) and benzopyrene (which produced strong inner filter effect across the useful wavelength range). Prediction was made on validation samples with a qualitative composition similar to the calibration set, and also on test samples containing an unexpected component (pyrene). In this latter case, U-PLS/RBL showed a unique success for the analysis of the calibrated component chrysene, achieving the useful second-order advantage.     

Removal efficiencies and attachment coefficients for Cryptosporidium in sandy alluvial riverbank sediment

Riverbank filtration has been shown to be effective for removing viable Cryptosporidium parvum oocysts. Drinking water systems that employ riverbank filtration may receive additional treatment credits beyond that which they can obtain using traditional engineering approaches. In order to develop guidance for removal effectiveness, screening level predictive modeling by colloid filtration theory combined with advection and dispersion modeling is potentially useful. Currently, only few studies have measured basic effective colloid filtration parameters for Cryptosporidium oocysts with naturally occurring riverbank sediments. In the focus of this study we conducted flow column experiments in triplicate and measured effective attachment rate coefficients for sandy river sediments of the Southern Great Plains which are low in organic matter. We found that for sediment sampled from these high-energy rivers there was no apparent dependency of C. parvum removal with carbon content, bacterial colony forming units, or with gross texture properties of the sands. The differences in particle size distribution for the sediments suggested that straining did not play a role in removal efficiency. First-order colloid attachment rate coefficients followed lognormal distribution functions. The coefficients also appeared to be unrelated to the differences in particle size distributions of the sediments, bacterial counts, or levels of total carbon or total organic carbon. Using Monte Carlo analyses, the lowest observed 5th percentile was 8.0 × 10⁻⁶ min⁻¹ and the highest observed 95th percentile was 1.6 × 10⁻³. Total log₁₀ removals ranged from 23 to 200 m⁻¹. These results have application for screening level colloid filtration modeling of riverbank filtration in these systems.     

Removal and fate of Cryptosporidium parvum, Clostridium perfringens and small-sized centric diatoms (Stephanodiscus hantzschii) in slow sand filters

The decimal elimination capacity (DEC) of slow sand filtration (SSF) for Cryptosporidium parvum was assessed to enable quantitative microbial risk analysis of a drinking water production plant. A mature pilot plant filter of 2.56m(2) was loaded with C. parvum oocysts and two other persistent organisms as potential surrogates; spores of Clostridium perfringens (SCP) and the small-sized (4-7microm) centric diatom (SSCD) Stephanodiscus hantzschii. Highly persistent micro-organisms that are retained in slow sand filters are expected to accumulate and eventually break through the filter bed. To investigate this phenomenon, a dosing period of 100 days was applied with an extended filtrate monitoring period of 150 days using large-volume sampling. Based on the breakthrough curves the DEC of the filter bed for oocysts was high and calculated to be 4.7log. During the extended filtrate monitoring period the spatial distribution of the retained organisms in the filter bed was determined. These data showed little risk of accumulation of oocysts in mature filters most likely due to predation by zooplankton. The DEC for the two surrogates, SCP and SSCD, was 3.6 and 1.8log, respectively. On basis of differences in transport behaviour, but mainly because of the high persistence compared to the persistence of oocysts, it was concluded that both spores of sulphite-reducing clostridia (incl. SCP) and SSCD are unsuited for use as surrogates for oocyst removal by slow sand filters. Further research is necessary to elucidate the role of predation in Cryptosporidium removal and the fate of consumed oocysts.     

Survival and viability of Helicobacter pylori after inoculation into chlorinated drinking water

The aim of this work was to assess the effect of chlorine water treatment on Helicobacter pylori and to study the succession of cellular alterations in response to chlorine exposure. H. pylori NCTC 11637 reference strain was used for inoculating water samples. The culturability, substrate responsiveness combined with fluorescent in situ hybridization detection (DVC-FISH assay), RNA content, DNA content, and mRNA changes of H. pylori cells were analyzed. Culturability was lost at 5 min in water with 0.96 mg/l of free chlorine. Viable cells were detected by DVC-FISH after 3h of exposure to chlorine but not after 24h. The percentage of coccoid forms was higher than spiral forms after 40s of chlorine exposure, but even after 24h, FISH detection revealed the presence of spiral cells. After 24h, amplification of the specific H. pylori 16S rDNA gene was achieved. Expression of the vacA gene was detected with the same intensity at all time points tested, demonstrating that these genes are expressed in non-culturable H. pylori cells. Levels of 16S rRNA were constant during the chlorine treatment, so killing of bacteria with chlorine probably does not involve ribosome degradation. According to our results, H. pylori could survive to disinfection practices normally used in drinking water treatment in the viable but non-culturable form, which would allow them to reach final consumption points and, at the same time, enable them to be undetectable by culture methods.     

Quantitative determination of octylphenol, nonylphenol, alkylphenol ethoxylates and alcohol ethoxylates by pressurized liquid extraction and liquid chromatography-mass spectrometry in soils treated with sewage sludges

Surfactants have one of the highest production rates of all organic chemicals. Non-ionic surfactants, especially alkylphenol ethoxylates, received most attention as precursors of estrogenic metabolic products generated during wastewater treatment. Alkylphenols (octyl and nonylphenol), alkylphenol polyethoxylates (APEOs), and alcohol ethoxylates (AEOs) have been determined in a Mediterranean forest soil (Mediterranean Rendzic Leptosol) amended with sludges from six waste water treatment plants (WWTPs) located in the Valencian Community. These compounds were isolated from soil by pressurized liquid extraction (PLE) using a mixture acetone-hexane (50:50 v/v), the extracts were cleaned up by solid-phase extraction (SPE) with C(18), and determined by liquid chromatography atmospheric pressure chemical ionization-mass spectrometry (LC-APCI-MS) using analytical standards for quantification. The method enabled high-reliable identification by monitoring the corresponding ammonium adduct [M+NH(3)](+) for AEOs and APEOs, and the deprotonated molecule [M-H](-) for octyl and nonylphenol. Recoveries, determined spiking soil samples at different concentrations, ranged from 89 to 94%, with limits of quantification from 1 to 100 microg kg(-1). Data obtained from a soil sample mixed with biosolids in the laboratory showed that these compounds are present at concentrations ranging from 0.02 to 5 mg kg(-1). According to these concentrations, levels of possible risk can be concluded for the presence of non-ionic surfactants in soil. However, further assessment will be necessary to establish the relationship between exposure and effect findings.     

Development of a multiplex real-time PCR assay for the detection of ruminant DNA

The U.S. Food and Drug Administration (FDA) has previously validated a real-time PCR-based assay that is currently being used by the FDA and several state laboratories as the official screening method. Due to several shortcomings to the assay, a multiplex real-time PCR assay (MRTA) to detect three ruminant species (bovine, caprine, and ovine) was developed using a lyophilized bead design. The assay contained two primer or probe sets: a "ruminant" set to detect bovine-, caprine-, and ovine-derived materials and a second set to serve as an internal PCR control, formatted using a lyophilized bead design. Performance of the assay was evaluated against stringent acceptance criteria developed by the FDA's Center for Veterinary Medicine's Office of Research. The MRTA for the detection of ruminant DNA passed the stringent acceptance criteria for specificity, sensitivity, and selectivity. The assay met sensitivity and reproducibility requirements by detecting 30 of 30 complete feed samples fortified with meals at 0.1 % (wt/wt) rendered material from each of the three ruminant species. The MRTA demonstrated 100 % selectivity (0.0 % false positives) for negative controls throughout the assessment period. The assay showed ruggedness in both sample selection and reagent preparation. Second and third analyst trials confirmed the quality of the written standard operating procedure with consistency of results. An external laboratory participating in a peer-verification trial demonstrated 100 % specificity in identifying bovine meat and bone meal, while exhibiting a 0.03 % rate of false positives. The assay demonstrated equal levels of sensitivity and reproducibility compared with the FDA's current validated real-time PCR assay. The assay detected three prohibited species in less than 1.5 h of total assay time, a significant improvement over the current real-time assay. These results demonstrated this assay's suitability for routine regulatory use both as a primary screening tool and as a confirmatory test.     

Cheese whey fermented with kefir micro‐organisms: Antagonism against Salmonella and immunomodulatory capacity

The antagonistic effect against Salmonella spp. and the immunomodulatory capacity of whey fermented with kefir grains and with three strains isolated from them – Lactobacillus plantarum CIDCA 8327, Lactobacillus kefiri CIDCA 8348 and Kluyveromyces marxianus var. marxianus CIDCA 8154 – were evaluated. Both fermented products interfered with the capacity of Salmonella spp. to associate and invade Caco‐2/TC7 cells and reduced up to the basal level the expression of the CCL20 in response to a pro‐inflammatory stimulus on Caco‐2 CCL20:luc cells. The products with potential application as probiotics obtained by fermentation of whey with kefir micro‐organisms represent an alternative to increase whey economic value.     

Properties of carbon nanotube reinforced linear low density polyethylene nanocomposites fabricated by cryogenic ball‐milling

A cryogenic ball‐milling process to produce polymer/CNT nanocomposites was investigated. Linear low density polyethylene was used as the matrix material and 1 wt % of multiwalled carbon nanotubes (MWCNT) was used as reinforcement. The influence of the milling time and balls size was evaluated. The morphology of the nanocomposite and the degree of dispersion of the MWCNTs were studied using scanning electron microscopy (SEM), visual inspection, and light transmission microscopy; ropes as well as aggregates of MWCNTs were observed, and there was evidence of wetting of the nanotubes by the matrix polymer. An increase of up to 28% in the elastic modulus (determined by tensile testing) with respect to the matrix was obtained. Differential scanning calorimetry (DSC) analysis showed evidence of increase in the degree of crystallization, a result of the nucleating capability of the carbon nanotubes in the matrix. The degradation temperature of the nanocomposites does not show significant variations with respect to the unfilled polymer. POLYM. COMPOS., 2011. © 2011 Society of Plastics Engineers     

The Discovery and Structure-Activity Evaluation of (+)-Floyocidin B and Synthetic Analogs

Tuberculosis represents one of the ten most common courses of death worldwide and the emergence of multidrug-resistant M. tuberculosis makes the discovery of novel anti-tuberculosis active structures an urgent priority. Here, we show that (+)-floyocidin B representing the first example of a novel dihydroisoquinoline class of fungus-derived natural products, displays promising antitubercular hit properties. (+)-Floyocidin B was identified by activity-guided extract screening and its structure was unambiguously determined by total synthesis. The absolute configuration was deduced from a key synthesis intermediate by single crystal X-ray diffraction analysis. A hit series was generated by the isolation of further natural congeners and the synthesis of analogs of (+)-floyocidin B. Extensive biological and physicochemical profiling of this series revealed first structure-activity relationships and set the basis for further optimization and development of this novel antitubercular scaffold.     

Effect of calcium chloride and moderate shear on β-lactoglobulin aggregation in processing-like conditions

The influence of two variables (moderate shear and calcium chloride concentration) on the properties of β-lactoglobulin (β-lg) aggregate suspensions obtained by dynamic heat treatment (85 °C for 60 s) was studied. Variations in calcium chloride concentration from 5.1 to 7.1 mM were imposed, and led to major changes in the aggregate properties. The characterization of the aggregate size was performed using three distinct methods: laser granulometer, dynamic light scattering (DLS) and focus beam reflectance measurement (FBRM). Viscosity and residual native fraction were also determined. Statistical analysis of experimental data underlines the important combined effect of the two variables and paves the way for new ways of controlling the aggregate functionalities. The calcium chloride concentration has an effect on the entire aggregation process, from native β-lg to large aggregates. On the other hand, shear only impacts the formation of the large aggregates.