Comparison of different twin-screw extraction conditions for the production of arabinoxylans.

The aim of this article is to compare two different sets of optimal conditions for twin-screw extraction of xylans and define their influence on the purification steps, combining ultrafiltration and industrial chromatography. Two xylan extracts were obtained by twin-screw extrusion of straw and bran. Condition 1 used a high straw/bran ratio (equal to 6) and high sodium hydroxide content, and condition 2 used a lower straw/bran ratio (equal to 2) and low sodium hydroxide content. Arabinoxylan extraction yields are slightly higher for conditions with low straw content (5.1% versus 4.4%). Nevertheless, these recovery yields remain between 9% and 10%. Ultrafiltration is as efficient as evaporation for polysaccharide concentration, with lower energy consumption, but also demineralizes the solution. The combination of ultrafiltration and chromatography gives partial purification of the extract with a final arabinoxylan purity ranging from 16% to 26%. This is slightly higher than by direct precipitation, but limited because all the large molecules such as proteins and lignins were retained by ultrafiltration.

Halomonas desiderata as a bacterial model to predict the possible biological nitrate reduction in concrete cells of nuclear waste disposals.

After closure of a waste disposal cell in a repository for radioactive waste, resaturation is likely to cause the release of soluble species contained in cement and bituminous matrices, such as ionic species (nitrates, sulfates, calcium and alkaline ions, etc.), organic matter (mainly organic acids), or gases (from steel containers and reinforced concrete structures as well as from radiolysis within the waste packages). However, in the presence of nitrates in the near-field of waste, the waste cell can initiate oxidative conditions leading to enhanced mobility of redox-sensitive radionuclides (RN). In biotic conditions and in the presence of organic matter and/or hydrogen as electron donors, nitrates may be microbiologically reduced, allowing a return to reducing conditions that promote the safety of storage. Our work aims to analyze the possible microbial reactivity of nitrates at the bitumen - concrete interface in conditions as close as possible to radioactive waste storage conditions in order (i) to evaluate the nitrate reaction kinetics; (ii) to identify the by-products (NO2(-), NH4(+), N2, N2O, etc.); and (iii) to discriminate between the roles of planktonic bacteria and those adhering as a biofilm structure in the denitrifying activity. Leaching experiments on solid matrices (bitumen and cement pastes) were first implemented to define the physicochemical conditions that microorganisms are likely to meet at the bitumen-concrete interface, e.g. highly alkaline pH conditions (10 < pH < 11) imposed by the cement matrix. The screening of a range of anaerobic denitrifying bacterial strains led us to select Halomonas desiderata as a model bacterium capable of catalyzing the reaction of nitrate reduction in these particular conditions of pH. The denitrifying activity of H. desiderata was quantified in a batch bioreactor in the presence of solid matrices and/or leachate from bitumen and cement matrices. Denitrification was relatively fast in the presence of cement matrix (<100 h) and 2-3 times slower in the presence of bituminous matrix (pH 9.7). The maximal rate of denitrification was approximately 0.063 mM h(-1) and some traces of nitrite were detected for a few hours (<2%). Overall, the presence of solid cement promoted the kinetics of denitrification. The inspection of the solid surfaces at the end of the experiment revealed the presence of a biofilm of H. desiderata on the cement paste surface. These attached bacteria showed a comparable denitrifying activity to planktonic bacterial culture. However, no colonization of bitumen was observed either by SEM or by epifluorescence microscopy.

Optimization of pressurized liquid extraction using a multivariate chemometric approach for the determination of anticancer drugs in sludge by ultra high performance liquid chromatography-tandem mass spectrometry.

The present paper describes an analytical method for the determination of 2 widely administered anticancer drugs, ifosfamide and cyclophosphamide, contained in sewage sludge. The method relies on the extraction from the solid matrix by pressurized liquid extraction, sample purification by solid-phase extraction and analysis by ultra high performance liquid chromatography coupled with tandem mass spectrometry. The different parameters affecting the extraction efficiency were optimized using an experimental design. Solvent nature was the most decisive factor for the extraction but interactions between some parameters also appeared very influent. The method was applied to seven different types of sludge for validation. The performances of the analytical method displayed high variability between sludges with limits of detection spanning more than one order of magnitude and confirming the relevance of multi-sample validation. Matrix effect has been determined as the most limiting analytical step for quantification with different extent depending on analyte and sludge nature. For each analyte, the use of deuterated standard spiked at the very beginning ensured the complete compensation of losses regardless of the sample nature. The suitability of the method between freshly spiked and aged samples has also been verified. The optimized method was applied to different sludge samples to determine the environmental levels of anticancer drugs. The compounds were detected in some samples reaching 42.5µg/kgDM in ifosfamide for the most contaminated sample.

Trace determination of linear alkylbenzene sulfonates: application in artificially polluted soil-carrots system.

Surfactants are widely used in household and industrial products. The risk of incorporation of linear alkylbenzene sulfonates (LAS) from biosolids, wastewater, and fertilizers land application to the food chain is being assessed at present by the European Union. In the present work, a complete analytical method for LAS trace determination has been developed and successfully applied to LAS (C10-C13) uptake in carrot plants used as model. These carrots were grown in soil with the trace organics compounds added directly into the plant containers in pure substances form. LAS trace determination (mug kg(-1) dry matter) in carrots samples was achieved by Soxtec apparatus and high-performance liquid chromatography-fluorescence detection. The methodology developed provides LAS determination at low detection limits (5 mug kg(-1) dry matter) for carrot sample (2 g dry matter) with good recoveries rate (>90%). Transfer of LAS has been followed into the various parts of the carrot plant. LAS are generally found in the carrot leaves and percentage transfer remains very low (0.02%).

Development and validation of methods for the trace determination of phthalates in sludge and vegetables.

A routine method which is simple, quick and precise has been set up and validated for phthalate analysis in environmental samples (tomato plants and sewage sludges). Six phthalates have been studied simultaneously: dimethylphthalate, diethylphthalate, di-n-butylphthalate, n-butylbenzylphthalate, di-2-ethyl-hexyl phthalate (DEHP) and di-n-octylphthalate. Optimization of sample, solvent extraction uses a Soxtec apparatus and extract purification with an a solid-phase extraction cartridge allows between 90 and 110% recovery of phthalates. Precise, sensitive and selective identification and quantifying of analytes is by GC-MS in the single ion monitoring mode. This protocol allows analytes with concentrations as low as 10 microg/kg dry matter (DM) to be determined from small (1-2 g DM) samples. This analytical method has been applied to the phthalate transfer study for agricultural recycling of sludges, where phthalate bioavailability has been studied in aquiculture using two types of experiments. Tomatoes have been grown in containers where the trace organics have been directly introduced as pure substances, and in a second experiment under the same growth conditions, sewage sludge has replaced the pure substances. Transfer of these trace organics has been followed into the various parts of the tomato plant and in general only the DEHP is worthy of note although its percentage transfer remains very low even in an experiment designed to maximize this.