Genomic characterization of a polyvalent hydrocarbonoclastic bacterium Pseudomonas sp. strain BUN14

Bioremediation offers a viable alternative for the reduction of contaminants from the environment, particularly petroleum and its recalcitrant derivatives. In this study, the ability of a strain of Pseudomonas BUN14 to degrade crude oil, pristane and dioxin compounds, and to produce biosurfactants, was investigated. BUN14 is a halotolerant strain isolated from polluted sediment recovered from the refinery harbor on the Bizerte coast, north Tunisia and capable of producing surfactants. The strain BUN14 was assembled into 22 contigs of 4,898,053 bp with a mean GC content of 62.4%. Whole genome phylogeny and comparative genome analyses showed that strain BUN14 could be affiliated with two validly described Pseudomonas Type Strains, P. kunmingensis DSM 25974T and P. chloritidismutans AW-1T. The current study, however, revealed that the two Type Strains are probably conspecific and, given the priority of the latter, we proposed that P. kunmingensis DSM 25974 is a heteronym of P. chloritidismutans AW-1T. Using GC-FID analysis, we determined that BUN14 was able to use a range of hydrocarbons (crude oil, pristane, dibenzofuran, dibenzothiophene, naphthalene) as a sole carbon source. Genome analysis of BUN14 revealed the presence of a large repertoire of proteins (154) related to xenobiotic biodegradation and metabolism. Thus, 44 proteins were linked to the pathways for complete degradation of benzoate and naphthalene. The annotation of conserved functional domains led to the detection of putative genes encoding enzymes of the rhamnolipid biosynthesis pathway. Overall, the polyvalent hydrocarbon degradation capacity of BUN14 makes it a promising candidate for application in the bioremediation of polluted saline environments

Étude du séchage au CO2 supercritique pour l'élaboration de matériaux nanostructurés : application aux aérogels de silice monolithiques

Aerogel-like nanostructured materials present a wide set of potential application fields. Among these materials, silica aerogels are known in particular for their thermal super-insulation capability and their transparency in the visible range. Their integration in double-glazing should offer an energetic gain in the building sector, especially through the reduction of heat consumption. For such an application, silica gels synthesised through a sol-gel process, should be dried supercritically in order to obtain large dimensions transparent and monolithic aerogel sheets. This thesis work aims to contribute to the amelioration of the supercritical CO2 drying process efficacity while focusing particularly on the supercritical CO2 washing phase. The phenomena occurring during this phase were studied by coupling experimental and theoretical approaches. The experimental approach is based on the instrumentation of a drying system and notably the implementation of an analysis loop. This metrological tool makes it possible to monitor on line the degree of advancement of the washing phase. The theoretical approach is based on an analytical model coupling diffusion phenomena through the nanoporosity of the gels and mass transfer phenomena in the autoclave. This double approach has allowed firstly to quantify the diffusion phenomena in reference experimental conditions. The effective diffusion coefficient of a model gel nanostructure was so determined. A first estimation of the washing phase duration was also obtained. Secondly, the influence of the variation of silica aerogel nanostructure on the diffusion phenomena was studied. The obtained results have led to a first correlation between the materials permeability and the effective diffusion coefficient. This study has also underlined the interest of an aging treatment by dissolution-reprecipitation phenomena prior to drying in order to shorten the supercritical washing phase duration.Les matériaux nanostructurés de type aérogels présentent des domaines d'applications potentielles très variés. Parmi ces matériaux, les aérogels de silice sont connus, notamment, pour leurs propriétés thermiques super-isolantes et leur transparence dans le domaine visible. Leur intégration au sein de double vitrage peut ainsi permettre d'envisager un gain énergétique dans le secteur du bâtiment, notamment au travers de la réduction des charges de chauffage. Pour une telle application, les gels de silice synthétisés par procédé sol-gel, doivent être séchés par voie supercritique afin d'obtenir des aérogels sous forme de blocs monolithiques transparents de grandes dimensions. L'objectif de ce travail de thèse est de contribuer à l'amélioration de l'efficacité du procédé de séchage dans les conditions du CO2 supercritique en s'attachant tout particulièrement à la phase de lavage au CO2 supercritique. Les phénomènes mis en jeu lors de cette phase ont été étudiés en couplant une approche expérimentale et une approche théorique. L'approche expérimentale repose sur l'instrumentation d'un banc de séchage notamment en implémentant une boucle d'analyse. Cet outil métrologique a permis de suivre en ligne le degré d'avancement de la phase de lavage. L'approche théorique repose sur l'utilisation d'un modèle analytique couplant les phénomènes de diffusion à travers la nanoporosité des gels et les phénomènes de transfert de masse dans l'autoclave. Cette double approche a permis dans un premier temps de quantifier les phénomènes de diffusion dans des conditions expérimentales de référence. Le coefficient de diffusion effectif d'une nanostructure modèle de gels de silice a été ainsi déterminé. Une première estimation de la durée de la phase de lavage a également été obtenue. Dans un second temps, l'influence de la variation de la nanostructure des aérogels de silice sur les phénomènes de diffusion a été étudiée. Les résultats obtenus ont permis d'aboutir à une première corrélation entre la perméabilité des matériaux et le coefficient de diffusion effectif. Cette étude a également souligné l'intérêt d'un traitement de vieillissement des gels par phénomènes de dissolution-reprécipitation préalablement au séchage en vue d'écourter la durée de la phase de lavage supercritique

Etude du séchage au co2 supercritique pour l élaboration de matériaux nanostructurés: application aux aérogels de silice monolithiques ( application aux aérogels de silice monolithiques)

PARIS-MINES ParisTech (751062310) / SudocSOPHIA ANTIPOLIS-Mines ParisTech (061522302) / SudocSudocFranceF

Current situation and perspectives in drug formulation by using supercritical fluid technology

International audienceSupercritical fluid (SCF) technology has been applied to drug product development over the last thirty years and drug particle generation using SCFs appears to be an efficient way to carry out drug formulation which will form end-products meeting targeted specifications. This article presents an overview of drug particle design using SCFs from a rather different perspective than usual, more focused on chemical and process engineering aspects. The main types of existing processes are described in a concise way and a focus is put on how to choose the right operating conditions considering both thermodynamic and hydrodynamic aspects. It is shown that the operating conditions and parameters can be easily optimized so as to facilitate the further process scale-up. Furthermore, the new trends in particle generation using SCFs are introduced, related either to new types of drug medicines that are treated or new ways of process implementation methods

Effect of operational conditions on the supercritical carbon dioxide impregnation of anti-inflammatory and antibiotic drugs in rigid commercial intraocular lenses

International audienceDrug/lense combinations have proven significant in the field of ocular therapeutics. The development of innovative systems and elaboration processes is an upcoming issue for ocular drug delivery. One challenging issue is the elaboration of drug loaded intraocular lenses (IOLs) to combine cataract surgery and post-operative treatments in a single procedure. In this work, we are studying the elaboration of such systems while using a green process using supercritical fluids for impregnating ophthalmic drugs on commercial IOLs. More particularly, rigid commercial intraocular lenses made from Poly (Methyl MethAcrylate) (PMMA), used in cataract surgery, are loaded with dexamethasone 21- phosphate disodium salt (DXP, an anti-inflammatory drug) and ciprofloxacin (CIP, an antibiotic) in order to prevent short- and mid-term postoperative complications.Supercritical impregnations were carried out in a batch mode and impregnation yields were determined through drug release kinetic studies in a solution simulating the aqueous humor. Before performing an experimental design, preliminary impregnation assays were conducted in order to delimit the operating domain. Transparent IOLs presenting an effective impregnation were obtained. The highest impregnation yields for DXP and CIP in PMMA IOLs were 18.3 and 2.8 μgdrug/mgIOL respectively. Despite the low solubility of each drug in the fluid phase, homogeneous and in-depth impregnations were successfully obtained with a prolonged drug delivery (about 40 days) for most impregnation experiments

Supercritical CO2, drying of silica aerogels synthetized in 2-propanol

International audienc

Solvent diffusion during the supercritical CO2 drying of silica aerogels.

CD-RO

Solubility of cefuroxime axetil in supercritical CO2: measurement and modeling

International audienceIn this study, an analytical dynamic method was optimized for small amounts of drugs and used to measure the solubility of cefuroxime axetil in supercritical CO2. After validating the experimental procedure with nimesulide, an active ingredient already studied in the literature, the solubility of cefuroxime axetil in supercritical CO2 was measured at temperatures varying from 308 to 328 K and pressures ranging between 8 and 25 MPa. Experimental values varied between 2.2 × 10-7 and 11.24 × 10-6 (in mole fraction) and a retrograde solubility behavior was observed.The solubility was correlated with semi-empirical density-based models: Kumar and Johnston, Mendez-Santiago and Teja, and Chrastil models. All three models successfully correlated the solubilities of cefuroxime axetil with an average deviation lower than 15 %

Diffusion During the Supercritical Drying of Silica Gels

International audienceDrying is the most critical elaboration step of large monolithic and crack-free silica aerogel plates. In the present work, we are studying the supercritical CO2 drying and more precisely the first step, here called the supercritical washing step. This phase consists of replacing the liquid phase contained in the nanopores with supercritical CO2. Within this study, this step is governed by molecular diffusion through the gels. These phenomena were investigated experimentally in order to estimate the duration of the washing step. The experimental results were then fitted with an analytical mass transfer model to identify the effective diffusion coefficient

Supercritical Drug Impregnation onto Intraocular Lenses

International audienc