State-of-the-art and challenges in the analysis of renewable gases.

The development of renewable and low-carbon gases for injection into the gas grid obtained by different processes such as anaerobic digestion, pyrogasification, hydrothermal gasification, and methanation, followed by upgrading steps, increases the demand for analysis and characterization in order to fully manage their integration into the gas value chain. If the analysis of the main compounds (methane, carbon dioxide, hydrogen, and carbon monoxide) is well described, the analysis of impurities in renewable gases remains more challenging due to their various natures and quantities. After a brief description of renewable and low-carbon methane production processes, the review focuses on the methods used for the analysis of the different compounds in renewable gases, from the main ones to impurities at ppbv levels. Gas chromatography (GC), coupled with different detectors, is the preferred technique, enabling the analysis and quantification of siloxanes, terpenes, oxygenates, and sulfur compounds. Recently, comprehensive two-dimensional GC has been applied to renewable gases, increasing the number of compounds detected. Non-chromatographic techniques are also reviewed. As sampling is of major importance in the search for reliable analyses, a whole section is devoted to this aspect. Among the available methods, pre-concentration on adsorbent tubes emerges as the most relevant solution.

Biofilm microenvironment induces a widespread adaptive amino-acid fermentation pathway conferring strong fitness advantage in Escherichia coli.

Bacterial metabolism has been studied primarily in liquid cultures, and exploration of other natural growth conditions may reveal new aspects of bacterial biology. Here, we investigate metabolic changes occurring when Escherichia coli grows as surface-attached biofilms, a common but still poorly characterized bacterial lifestyle. We show that E. coli adapts to hypoxic conditions prevailing within biofilms by reducing the amino acid threonine into 1-propanol, an important industrial commodity not known to be naturally produced by Enterobacteriaceae. We demonstrate that threonine degradation corresponds to a fermentation process maintaining cellular redox balance, which confers a strong fitness advantage during anaerobic and biofilm growth but not in aerobic conditions. Whereas our study identifies a fermentation pathway known in Clostridia but previously undocumented in Enterobacteriaceae, it also provides novel insight into how growth in anaerobic biofilm microenvironments can trigger adaptive metabolic pathways edging out competition with in mixed bacterial communities.

A New Transcutaneous Method for Breast Cancer Detection with Dogs.

We developed a new transcutaneous method for breast cancer detection with dogs: 2 dogs were trained to sniff skin secretion samples on compresses that had been worn overnight by women on their breast, and to recognize a breast cancer sample among 4 samples. During the test, the dogs recognized 90.3% of skin secretion breast cancer samples. This proof-of-concept study opens new avenues for the development of a reliable cancer diagnostic tool integrating olfactory abilities of dogs.

Volatile Organic Compounds of Malignant Breast Cancer Wounds: Identification and Odors.

INTRODUCTION: During the metabolic processes of malignant wounds, bacteria produce a large amount of volatile organic compounds (VOCs) that are responsible for malodors and may have a major impact on the patient's quality of life with a risk of isolation. OBJECTIVE: A translational study was conducted on 32 malignant breast wounds by combining the identification of bacterial strains present on wounds, the identification of VOCs produced by these bacterial strains, and sensory evaluation to assess odor intensity and quality of odorous bacteria. MATERIALS AND METHODS: Thirty-two patients with malignant breast cancer wounds > 10 cm2 at various stages of the disease (curative or palliative) were included in the protocol. Volatile organic compounds were collected from primary dressings by headspace solid-phase microextraction and then analyzed by gas chromatography separation coupled with a mass spectrometer detector analysis. Microbiological samplings were taken and analyzed on agar plates. The odors of selected bacteria were assessed by a panel of staff members. RESULTS: Proteus mirabilis and Fusobacterium necrophorum seem to produce the strongest and most typical malignant wound odor. The VOCs were analyzed and dimethyl disulfide, dimethyl trisulfide, phenol, indole, and 3-methylbutanal were found to be produced by bacteria generating the most typical wound odor. CONCLUSIONS: This study suggests the bacteria present in wounds may be responsible for odors. In addition, these findings could pave the way to engineer new types of dressings and to develop an evaluation method to assess their efficiency both quantitatively and qualitatively as well as improve quality of palliative care and comfort for women with malignant wounds.

Use of solid-phase microextraction coupled with gas chromatography for the determination of residual solvents in pharmaceutical products.

The aim of this work was to prove that solid-phase microextraction coupled with gas chromatography could be used for the determination and quantification of residual solvents in drugs. Four solvents were selected for the experiments: ethanol, cyclohexane, triethylamine and pyridine, together with a model powdered drug substance. Several kinds of fibers, together with the extraction mode, were evaluated to determine the most appropriate one for the simultaneous extraction of the four solvents. The most promising conditions were obtained with the Carboxen-polydimethylsiloxane fiber in the headspace of the aqueous solution that contained the dissolved powder. A concentrated phosphate buffer was added to the aqueous solution to set the pH at 9.6 in order to enable good extraction of triethylamine, and the optimum extraction time was experimentally determined. A multi-criteria optimization was also carried out by means of design of experiments to optimize remaining parameters: the extraction temperature was set at 40 degrees C, the ionic strength at 1.77 mol (l-1) and the volume of the aqueous solution at 7.2 ml. The method of standard additions was used for quantitative analysis. Its performance was evaluated and validated: the pooled RSD was around 15%, the limits of detection were all of the ppb level and the method was both accurate and linear.

Simultaneous determination of "earthy-musty" odorous haloanisoles and their corresponding halophenols in water samples using solid-phase microextraction coupled to gas chromatography with electron-capture detection.

Certain haloanisoles present at trace levels cause a large part of earthy-musty off-flavor problems in drinking water. These potent odorous chemicals come mainly through biomethylation of their corresponding halopenols. To enable the investigation of both families of compounds, a method involving solid-phase microextraction (SPME) was developed and the main parameters governing SPME were optimized. This method allows the simultaneous quantification of haloanisoles and halophenols at levels ranging from 1 to 100 or 250 ng/l, with detection limits of about 0.5 ng/l and could be applied to potable as well as raw surface waters.

Online preconcentration using monoliths in electrochromatography capillary format and microchips.

Online preconcentration and separation of analytes using an in situ photopolymerized hexyl acrylate-based monolith stationary phase was evaluated using electrochromatography in capillary format and microchip. The band broadening occurring during the preconcentration process by frontal electrochromatography and during the desorption process by elution electrochromatography was studied. The hexyl acrylate-based monolith provides high retention for neutral analytes allowing the handling of large sample volumes and its structure allows rapid mass transfer, thus reducing the band broadening. For moderately polar analytes such as mono-chlorophenols that are slightly retained in water, it was shown that enrichment factors up to 3500 can be obtained by a hydrodynamic injection of several bed volumes for 120 min under 0.8 MPa with a decrease in efficiency of 50% and a decrease of 30% for the resolution between 2- and 3-chlorophenol. An 8 min preconcentration time allows enrichment factors above 100 for polyaromatic hydrocarbons. The interest of these monoliths when synthesized in microchip is also demonstrated. A 200-fold enrichment was easily obtained for PAHs with only 1 min as preconcentration time, without decrease in efficiency.