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Dive into the research topics where Moez Rhimi is active.

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Featured researches published by Moez Rhimi.


Bioresource Technology | 2010

The acid tolerant l-arabinose isomerase from the food grade Lactobacillus sakei 23K is an attractive d-tagatose producer

Moez Rhimi; Rimeh Ilhammami; Goran Bajic; Samira Boudebbouze; Emmanuelle Maguin; Richard Haser; Nushin Aghajari

The araA gene encoding an L-arabinose isomerase (L-AI) from the psychrotrophic and food grade Lactobacillus sakei 23K was cloned, sequenced and over-expressed in Escherichia coli. The recombinant enzyme has an apparent molecular weight of nearly 220 kDa, suggesting it is a tetramer of four 54 kDa monomers. The enzyme is distinguishable from previously reported L-AIs by its high activity and stability at temperatures from 4 to 40 degrees C, and pH from 3 to 8, and by its low metal requirement of only 0.8 mM Mn(2+) and 0.8 mM Mg(2+) for its maximal activity and thermostability. Enzyme kinetic studies showed that this enzyme displays a high catalytic efficiency allowing D-galactose bioconversion rates of 20% and 36% at 10 and 45 degrees C, respectively, which are useful for commercial production of D-tagatose.


Journal of Bacteriology | 2007

Probing the Essential Catalytic Residues and Substrate Affinity in the Thermoactive Bacillus stearothermophilus US100 l-Arabinose Isomerase by Site-Directed Mutagenesis

Moez Rhimi; Michel Juy; Nushin Aghajari; Richard Haser; Samir Bejar

The L-arabinose isomerase (L-AI) from Bacillus stearothermophilus US100 is characterized by its high thermoactivity and catalytic efficiency. Furthermore, as opposed to the majority of l-arabinose isomerases, this enzyme requires metallic ions for its thermostability rather than for its activity. These features make US100 L-AI attractive as a template for industrial use. Based on previously solved crystal structures and sequence alignments, we identified amino acids that are putatively important for the US100 L-AI isomerization reaction. Among these, E306, E331, H348, and H447, which correspond to the suggested essential catalytic amino acids of the L-fucose isomerase and the L-arabinose isomerase from Escherichia coli, are presumed to be the active-site residues of US100 L-AI. Site-directed mutagenesis confirmed that the mutation of these residues resulted in totally inactive proteins, thus demonstrating their critical role in the enzyme activity. A homology model of US100 L-AI was constructed, and its analysis highlighted another set of residues which may be crucial for the recognition and processing of substrates; hence, these residues were subjected to mutagenesis studies. The replacement of the D308, F329, E351, and H446 amino acids with alanine seriously affected the enzyme activities, and suggestions about the roles of these residues in the catalytic mechanism are given. The mutation F279Q strongly increased the enzymes affinity for L-fucose and decreased the affinity for L-arabinose compared to that of the wild-type enzyme, showing the implication of this amino acid in substrate recognition.


World Journal of Biological Chemistry | 2013

Molecular recognition by gold, silver and copper nanoparticles

Yannick Tauran; Arnaud Brioude; Anthony W. Coleman; Moez Rhimi; Beonjoom Kim

The intrinsic physical properties of the noble metal nanoparticles, which are highly sensitive to the nature of their local molecular environment, make such systems ideal for the detection of molecular recognition events. The current review describes the state of the art concerning molecular recognition of Noble metal nanoparticles. In the first part the preparation of such nanoparticles is discussed along with methods of capping and stabilization. A brief discussion of the three common methods of functionalization: Electrostatic adsorption; Chemisorption; Affinity-based coordination is given. In the second section a discussion of the optical and electrical properties of nanoparticles is given to aid the reader in understanding the use of such properties in molecular recognition. In the main section the various types of capping agents for molecular recognition; nucleic acid coatings, protein coatings and molecules from the family of supramolecular chemistry are described along with their numerous applications. Emphasis for the nucleic acids is on complementary oligonucleotide and aptamer recognition. For the proteins the recognition properties of antibodies form the core of the section. With respect to the supramolecular systems the cyclodextrins, calix[n]arenes, dendrimers, crown ethers and the cucurbitales are treated in depth. Finally a short section deals with the possible toxicity of the nanoparticles, a concern in public health.


Environmental Microbiology | 2016

Beneficial metabolic effects of selected probiotics on diet‐induced obesity and insulin resistance in mice are associated with improvement of dysbiotic gut microbiota

Jeanne Alard; Véronique Lehrter; Moez Rhimi; Irène Mangin; Véronique Peucelle; Anne-Laure Abraham; Mahendra Mariadassou; Emmanuelle Maguin; Anne-Judith Waligora-Dupriet; Bruno Pot; Isabelle Wolowczuk; Corinne Grangette

Alterations in gut microbiota composition and diversity were suggested to play a role in the development of obesity, a chronic subclinical inflammatory condition. We here evaluated the impact of oral consumption of a monostrain or multi-strain probiotic preparation in high-fat diet-induced obese mice. We observed a strain-specific effect and reported dissociation between the capacity of probiotics to dampen adipose tissue inflammation and to limit body weight gain. A multi-strain mixture was able to improve adiposity, insulin resistance and dyslipidemia through adipose tissue immune cell-remodelling, mainly affecting macrophages. At the gut level, the mixture modified the uptake of fatty acids and restored the expression level of the short-chain fatty acid receptor GPR43. These beneficial effects were associated with changes in the microbiota composition, such as the restoration of the abundance of Akkermansia muciniphila and Rikenellaceae and the decrease of other taxa like Lactobacillaceae. Using an in vitro gut model, we further showed that the probiotic mixture favours the production of butyrate and propionate. Our findings provide crucial clues for the design and use of more efficient probiotic preparations in obesity management and may bring new insights into the mechanisms by which host-microbe interactions govern such protective effects.


Research in Microbiology | 2010

Efficient bioconversion of lactose in milk and whey: immobilization and biochemical characterization of a β-galactosidase from the dairy Streptococcus thermophilus LMD9 strain

Moez Rhimi; Anaïs Boisson; Magali Dejob; Samira Boudebouze; Emmanuelle Maguin; Richard Haser; Nushin Aghajari

The gene encoding beta-galactosidase from dairy Streptococcus thermophilus strain LMD9 was cloned, sequenced and expressed in Escherichia coli. The recombinant enzyme was purified and showed high specific activity of 464 U/mg. This protein displays a homotetrameric arrangement composed of four 118 kDa monomers. Monitoring of the activity showed that this enzyme was optimally active at a wide range of temperatures (25-40 degrees C) and at pH from 6.5 to 7.5. Immobilization of the recombinant E. coli in alginate beads clearly enhanced the enzyme activity at various temperatures, including 4 and 50 degrees C, and at pH values from 4.0 to 8.5. Stability studies indicated that this biocatalyst has high stability within a broad range of temperatures and pH. This stability was improved not only by addition of 1 mM of Mn(2+) and 1.2 mM Mg(2+), but essentially through immobilization. The remarkable bioconversion rates of lactose in milk and whey at different temperatures revealed the attractive catalytic efficiency of this enzyme, thus promoting its use for lactose hydrolysis in milk and other dairy products.


Microbial Cell Factories | 2011

The acid-tolerant L-arabinose isomerase from the mesophilic Shewanella sp. ANA-3 is highly active at low temperatures

Moez Rhimi; Goran Bajic; Rimeh Ilhammami; Samira Boudebbouze; Emmanuelle Maguin; Richard Haser; Nushin Aghajari

BackgroundL-arabinose isomerases catalyse the isomerization of L-arabinose into L-ribulose at insight biological systems. At industrial scale of this enzyme is used for the bioconversion of D-galactose into D-tagatose which has many applications in pharmaceutical and agro-food industries. The isomerization reaction is thermodynamically equilibrated, and therefore the bioconversion rates is shifted towards tagatose when the temperature is increased. Moreover, to prevent secondary reactions it will be of interest to operate at low pH. The profitability of this D-tagatose production process is mainly related to the use of lactose as cheaper raw material. In many dairy products it will be interesting to produce D-tagatose during storage. This requires an efficient L-arabinose isomerase acting at low temperature and pH values.ResultsThe gene encoding the L-arabinose isomerase from Shewanella sp. ANA-3 was cloned and overexpressed in Escherichia coli. The purified protein has a tetrameric arrangement composed by four identical 55 kDa subunits. The biochemical characterization of this enzyme showed that it was distinguishable by its maximal activity at low temperatures comprised between 15-35°C. Interestingly, this biocatalyst preserves more than 85% of its activity in a broad range of temperatures from 4.0 to 45°C. Shewanella sp. ANA-3 L-arabinose isomerase was also optimally active at pH 5.5-6.5 and maintained over 80% of its activity at large pH values from 4.0 to 8.5. Furthermore, this enzyme exhibited a weak requirement for metallic ions for its activity evaluated at 0.6 mM Mn2+. Stability studies showed that this protein is highly stable mainly at low temperature and pH values. Remarkably, T268K mutation clearly enhances the enzyme stability at low pH values. Use of this L-arabinose isomerase for D-tagatose production allows the achievement of attractive bioconversion rates of 16% at 4°C and 34% at 35°C.ConclusionsHere we reported the purification and the biochemical characterization of the novel Shewanella sp. ANA-3 L-arabinose isomerase. Determination of the biochemical properties demonstrated that this enzyme was highly active at low temperatures. The generated T268K mutant displays an increase of the enzyme stability essentially at low pH. These features seem to be very attractive for the bioconversion of D-galactose into D-tagatose at low temperature which is very interesting from industrial point of view.


Chemical Communications | 2013

Discriminatory antibacterial effects of calix[n]arene capped silver nanoparticles with regard to Gram positive and Gram negative bacteria

Samira Boudebbouze; Anthony W. Coleman; Yannick Tauran; Héla Mkaouar; Florent Perret; Alexandrine Garnier; Arnaud Brioude; Beomjoon Kim; Emmanuelle Maguin; Moez Rhimi

Silver nanoparticles capped with nine different sulphonated calix[n]arenes were tested for their anti-bacterial effects against B. subtilis and E. coli at an apparent concentration of 100 nM in calix[n]arene. The results show the para-sulphonato-calix[n]arenes are active against Gram positive bacteria and the derivatives having sulphonate groups at both para and alkyl terminal positions are active against Gram negative bacteria. The calix[6]arene derivative with only O-alkyl sulphonate groups shows bactericidal activity.


Recent Patents on Dna & Gene Sequences | 2011

Bacterial L-Arabinose Isomerases: Industrial Application for D-Tagatose Production

Samira Boudebbouze; Emmanuelle Maguin; Moez Rhimi

D-tagatose is a natural monosaccharide with a low caloric value and has an anti-hyperglycemiant effect. This hexose has potential applications both in pharmaceutical and agro-food industries. However, the use of D-tagatose remains limited by its production cost. Many production procedures including chemical and biological processes were developed and patented. The most profitable production way is based on the use of L-arabinose isomerase which allows the manufacture of D-tagatose with an attractive rate. Future developments are focused on the generation of L-arabinose isomerases having biochemical properties satisfying the industrial applications. This report provides a brief review of the most recent patents that have been published relating to this area.


American Journal of Physiology-endocrinology and Metabolism | 2018

Reduced obesity, diabetes and steatosis upon cinnamon and grape pomace are associated with changes in gut microbiota and markers of gut barrier.

Matthias Van Hul; Lucie Geurts; Hubert Plovier; Céline Druart; Amandine Everard; Marcus Ståhlman; Moez Rhimi; Kleopatra Chira; Pierre-Louis Teissedre; Nathalie M. Delzenne; Emmanuelle Maguin; Angèle Guilbot; Amandine Brochot; Philippe Gérard; Fredrik Bäckhed; Patrice D. Cani

Increasing evidence suggests that polyphenols have a significant potential in the prevention and treatment of risk factors associated with metabolic syndrome. The objective of this study was to assess the metabolic outcomes of two polyphenol-containing extracts from cinnamon bark (CBE) and grape pomace (GPE) on C57BL/6J mice fed a high-fat diet (HFD) for 8 wk. Both CBE and GPE were able to decrease fat mass gain and adipose tissue inflammation in mice fed a HFD without reducing food intake. This was associated with reduced liver steatosis and lower plasma nonesterified fatty acid levels. We also observed a beneficial effect on glucose homeostasis, as evidenced by an improved glucose tolerance and a lower insulin resistance index. These ameliorations of the overall metabolic profile were associated with a significant impact on the microbial composition, which was more profound for the GPE than for the CBE. At the genus level, Peptococcus were decreased in the CBE group. In the GPE-treated group, several key genera that have been previously found to be linked with HFD, metabolic effects, and gut barrier integrity were affected: we observed a decrease of Desulfovibrio, Lactococcus, whereas Allobaculum and Roseburia were increased. In addition, the expression of several antimicrobial peptides and tight junction proteins was increased in response to both CBE and GPE supplementation, indicating an improvement of the gut barrier function. Collectively, these data suggest that CBE and GPE can ameliorate the overall metabolic profile of mice on a high-fat diet, partly by acting on the gut microbiota.


Genome Announcements | 2014

Genome Sequence of “Candidatus Arthromitus” sp. Strain SFB-Mouse-NL, a Commensal Bacterium with a Key Role in Postnatal Maturation of Gut Immune Functions

Alexander Bolotin; Tomas de Wouters; Pamela Schnupf; Christiane Bouchier; Valentin Loux; Moez Rhimi; Alexandre Jamet; Rozenn Dervyn; Samira Boudebbouze; Hervé M. Blottière; Alexei Sorokin; Johannes Snel; Nadine Cerf-Bensussan; Valérie Gaboriau-Routhiau; Maarten van de Guchte; Emmanuelle Maguin

ABSTRACT “Candidatus Arthromitus” sp. strain SFB-mouse-NL (SFB, segmented filamentous bacteria) is a commensal bacterium necessary for inducing the postnatal maturation of homeostatic innate and adaptive immune responses in the mouse gut. Here, we report the genome sequence of this bacterium, which sets it apart from earlier sequenced mouse SFB isolates.

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Emmanuelle Maguin

Institut national de la recherche agronomique

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Samira Boudebbouze

Institut national de la recherche agronomique

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Anthony W. Coleman

Centre national de la recherche scientifique

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Héla Mkaouar

Institut national de la recherche agronomique

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