I Fliss

Laval University, Québec, Quebec, Canada

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Publications (114)255.96 Total impact

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    ABSTRACT: The impact of fatty acids on the growth of lactobacilli and bifidobacteria was studied to gain insight into the beneficial effects of conjugated linoleic acid (CLA) and probiotics. Milk was enriched with CLA by adding 4% safflower oil to the cow diet, by emulsifying synthetic CLA as free fatty acids, or by emulsifying CLA as triacylglycerol, then adjusted to 1.0% or 3.25% fat and digested in a gastro-intestinal simulator. The residual fatty acid contents of milk samples containing initial fat contents of 1.0% and 3.25% were significantly different after 6 h digestion. Milk enriched with synthetic CLA and adjusted to 1.0% fat appeared to provide a digest that allowed growth of both Lactobacillus rhamnosus R0011 and Lb. rhamnosus LGG; adjustment to 3.25% fat decreased viable LGG slightly. Digestion of milk containing 3.25% fat appeared to yield a residual fatty acid mixture that may be slightly bactericidal or simply bacteriostatic.
    International Dairy Journal 07/2014; · 2.33 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the antibacterial and antifungal activities of water-soluble extracts (WSEs) from different types of cheeses against several food-borne pathogens. A total of five commercial cheeses manufactured in Canada were selected namely Mozzarella, Gouda, Swiss, and old and medium Cheddar. WSEs were ultrafiltrated through 10 kDa cutoff membranes and desalted using Sep-Pak cleanup column. Resulting peptide fractions were subject to physicochemical characterization and assessment for their antimicrobial activity against bacteria (Listeria ivanovii, Listeria monocytogenes, Escherichia coli MC4100, and E. coli O157:H7) and filamentous fungi (Aspergillus, Mucor, Fusarium, and Penicillium). Mozzarella and Gouda WSEs were the most active and inhibited with L. monocytogenes significantly, with respective reductions of 3.83 ± 0.15 and 2.93 ± 0.33 log. After desalting and organic acids removal, Mozzarella and Gouda WSEs produced 3-log reductions of L. ivanovii and E. coli MC4100, with minimal inhibitory concentration (MIC) values ranging 8.5–17 mg.mL−1. At a concentration of 34 mg.mL−1, all cheese peptidic WSEs induced a delay in spore germination. All WSEs were equally active against Fusarium sp., with a minimal concentration of 17 mg.mL−1. Gouda, Mozzarella, and medium Cheddar WSE were the strongest inhibitors in the case of Aspergillus versicolor and Mucor racemosus (17 mg.mL−1), whereas these spores were less sensitive to old Cheddar and Swiss WSE (34 mg.mL−1). This study demonstrates that peptidic WSEs of commercial cheeses manufactured in Canada exhibit antibacterial and antifungal activities, which may offer a promising alternative for purposes of food preservation.
    Dairy Science and Technology 04/2014; · 1.38 Impact Factor
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    ABSTRACT: The aim of this study was to isolate new bacteriocinogenic strains with putative probiotic potential from various Tunisian fermented milks. A total of 44 Gram-positive catalase-negative isolates were colony-purified and screened for antimicrobial activity. Of inhibitory isolates, four were identified as Enterococcus durans and one as Enterococcus faecalis using 16S rRNA gene sequence. The five strains were sensitive to penicillin G, all aminoglycosides tested, to the vancomycin, tetracycline, and chloramphenicol, and E. durans 42G and E. faecalis 61B were resistant to erythromycin. The antimicrobial substances were sensitive to proteolytic enzymes and had good biochemical stability. E. durans 61A showed a good resistance to gastric and small intestinal secretions, but were more sensitive to the duodenal conditions. Considering the safety and the stability under simulated gastrointestinal tract, it appears that the bacteriocinogenic strain E. durans 61A is a good candidate for its application as novel probiotic strain in the food industry.
    Archives of Microbiology 03/2014; · 1.91 Impact Factor
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    ABSTRACT: The number of identified and characterized bioactive peptides derived from milk proteins is increasing. Although many antimicrobial peptides of dairy origin are now well known, important structural and functional information is still missing or unavailable to potential users. The compilation of such information in one centralized resource such as a database would facilitate the study of the potential of these peptides as natural alternatives for food preservation or to help thwart antibiotic resistance in pathogenic bacteria. To achieve this goal, we established MilkAMP, a new database that contains valuable information on antimicrobial peptides of dairy origin, including microbiological and physicochemical data. The current release of MilkAMP contains 371 entries, including 9 hydrolysates, 299 antimicrobial peptides, 23 peptides predicted as antimicrobial, and 40 non-active peptides. Freely available at http://milkampdb.org/, this database should be useful to help develop uses of biologically active peptides in both the pharmaceutical and food sectors. As more information about antimicrobial peptides becomes available, the database will be expanded and improved accordingly.
    Dairy Science and Technology 03/2014; 94(2). · 1.38 Impact Factor
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    ABSTRACT: doi: 10.1080/87559129.2014.896017
    Food Reviews International 02/2014; · 1.92 Impact Factor
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    ABSTRACT: The aim of this study was to evaluate the antibacterial activity of newly synthesized triaryl butene analogues of tamoxifen. Several compounds were synthesized and converted to citrate salts to ensure greater solubility. Four compounds showed significant antibacterial activity at micromolar concentrations against Gram-positive and Gram-negative foodborne pathogens including Listeria monocytogenes, Listeria ivanovii, Enterococcus faecalis, Staphylococcus aureus and Escherichia coli. Two compounds at 50 μM, caused only 7.8 and 11% hemolysis. One of these as well as the remaining two caused high K+ and Na+ efflux from bacterial cells. Ultrastructural alterations were also visible using transmission electron microscopy, which revealed severe damage of the inner or outer membrane of E. coli. L. ivanovii showed swelling, corrugations and similar damage indicating a loss of cell-wall integrity. Organometallic compounds may offer interesting opportunities for the design of novel classes of antimicrobial compounds.
    European Journal of Medicinal Chemistry 02/2014; · 3.43 Impact Factor
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    ABSTRACT: The intestinal absorption of fatty acids from milk, especially conjugated linoleic acids (CLA), was evaluated using an in vitro simulator. Milk was enriched with c9,t11 CLA by feeding a cow a diet containing 4% safflower oil or by emulsifying synthetic CLA in the form of free fatty acid or triacylglycerol, then standardized to 1.0% or 3.25% fat. Fatty acid bioavailability depended on chain length, presence of double bonds, and the percentage of fat. Absorption was more efficient in the presence of 1.0% fat. The bioavailability of c9,t11 CLA at 3.25% fat was 89% in the milk from the cow fed the safflower oil diet, and 85% and 71% in milk enriched with synthetic free CLA and synthetic CLA in the form of triacylglycerol, respectively. At 1.0% fat, these values were 90%, 99% and 96%, respectively, suggesting that bioavailability of CLA in milk is affected by the percentage of fat present.
    International Dairy Journal. 01/2014;
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    ABSTRACT: The aim of this work is to study the expression of stress genes and those involved in pediocin and nisin production in Pediococcus acidilactici UL5 and Lactococcus lactis ATCC11454 under simulated gastrointestinal (GI) physiological conditions. The two strains were fed to a dynamic GI model (TIM-1). Samples were taken from different compartments and analysed for strain survival as well as for the expression of pediocin PA-1 operon, nisin A production gene and stress genes using RT-qPCR. Ileal-delivered efflux showed a survival rate of 17 and 0·0007% for Ped. acidilactici and La. lactis, respectively. Pediocin operon genes from stressed cells were generally expressed at least at the same level as for unstressed cells. However, pedA is up-regulated in the effluent at 120 and 180 min. Nisin A genes were always up-regulated with particularly in the stomach after 70 min compared with control. Bacteriocin production of Ped. acidilactici UL5 and Lc. lactis ATCC 11454 are not affected by upper GI simulated conditions and thus could be considered as relevant probiotic candidates. This study demonstrates the capacity of lactic acid bacteria to survive and express their bacteriocins genes under simulated GI conditions.
    Journal of Applied Microbiology 11/2013; · 2.20 Impact Factor
  • Journal of Functional Foods 04/2013; 5(2):706-714. · 2.63 Impact Factor
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    ABSTRACT: Ultrafiltration permeate of whey protein tryptic hydrolyzate was processed by nanofiltration (NF) to obtain retentate (NFR) and permeate (NFP) that were then tested as inhibitors of Listeria, Staphylococcus aureus and Escherichia coli. NFR at 20 mg mL�1 was most effective as an inhibitor (P < 0.001); whereas E. coli was relatively resistant, the effect on Listeria and S. aureus was greater at 20 mg mL�1 than at 10 mg mL�1 (P < 0.01). Peptide analysis revealed that NFR was rich in anionic peptides over eight amino acid residues in length. The antibacterial activity of two anionic peptides (84-91 and 125-135) and a cationic peptide (36-42) derived from b-lactoglobulin was tested. Peptide 125-135 was more inhibitory (P < 0.05) than peptide 84e91 against Listeria monocytogenes and S. aureus; peptide 36e42 was not inhibitory. NFR appears to have potential as a natural bio-preservative.
    International Dairy Journal 02/2013; 28(2):94-101. · 2.33 Impact Factor
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    ABSTRACT: The efficacy of an anionic peptides-enriched extract (APEE), produced by nanofiltration of a tryptic hydrolysate from whey proteins, to inhibit the growth of Listeria innocua and Listeria monocytogenes in reconstituted Cheddar cheese was studied. The antimicrobial activity of APEE in reconstituted cheese was greater against L. monocytogenes than L. innocua and was higher in storage at 30 �C than at 4 �C. The combination of 20 mg g�1 of APEE and 1.75% salt/moisture (S/M) in cheeses incubated for 7 days at 30 �C was the most efficient condition to inhibit the growth of Listeria. Using these conditions, L. monocytogenes counts were significantly reduced by 1.1 and 1.5 log cfu g�1, compared with cheeses without APEE and prepared with lactococci at 1.75 and 3.5% S/M, respectively. These results suggest that antimicrobial anionic peptides from whey proteins can contribute to control pathogen in reduced-salt Cheddar cheeses.
    International Dairy Journal 01/2013; 32:6-12. · 2.33 Impact Factor
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    ABSTRACT: Listeria monocytogenes is responsible for severe foodborne infections, which can be life-threatening especially for infants and elderly populations. The emergence of antibiotic-resistant pathogens has stimulated the search for new strategies, such as the use of bacteriocins, to prevent or cure foodborne infectious diseases in the intestine. In this study, we evaluated the efficacy of the bacteriocin pediocin PA-1 from Pediococcus acidilactici UL5 to inhibit Listeria ivanovii, used as a surrogate for L. monocytogenes, under physiological conditions of the terminal ileum, simulated in a continuous in vitro fermentation model. A fecal sample from a healthy adult was immobilized and propagated for 30 days in a continuous stirred tank reactor, fed with a nutritive medium simulating the ileal chime (pH 7.5). After reaching a pseudo-steady state, the reactor was inoculated five times with L. ivanovii to reach a final concentration of 107 CFU/ml within the reactor. Two spikes of L. ivanovii without adjunction of pediocin PA-1 served as control assays, and three other spikes were done to test the effects of three concentrations of pediocin PA-1 corresponding to 2, 3, and 5× the minimum inhibitory concentration (MIC) active against L. ivanovii. The concentration of L. ivanovii in the reactor was followed for 8 h using the PALCAM selective medium. The different groups of commensal bacteria were enumerated on selective medium or using fluorescence in situ hybridization. Our data showed that pediocin PA-1 is stable in the ileum conditions and that it is able to exert its inhibition activity against L. ivanovii in a dose-dependent manner. The addition of pediocin PA-1 at 5 × MIC induced a complete disappearance of L. ivanovii (5 log reduction) within 5 h, compared to a reduction of 2 logs, corresponding to the washout phenomenon, when no pediocin PA-1 was added. Reduction of 0.8 and 1.3 logs within 8 h was also obtained with the addition of 2 and 3 × MIC, respectively. The same experiment has shown that addition of pediocin-PA1 in the reactor had a negligible effect on the balance of commensal bacteria.
    Probiotics and Antimicrobial Proteins 12/2012; 4(4):250-258.
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    ABSTRACT: AIMS: The aim of this study is to evaluate the capacity of three bacteriocin producers, namely Lactococcus lactis subsp. lactis biovar diacetylactis UL719 (nisin Z producer), Lactococcus lactis ATCC 11454 (nisin A producer), and Pediococcus acidilactici UL5 (pediocin PA-1 producer), to grow and produce their active bacteriocins in Macfarlane broth, which mimics the nutrient composition encountered in the human large intestine.s METHODS AND RESULTS: The three bacteriocin-producing strains were grown in Macfarlane broth and in MRS broth. For each strain, the bacterial count, pH drop and production of organic acids and bacteriocins were measured for different period of time. The ability of the probiotic candidates to inhibit Listeria ivanovii HPB 28 in co-culture in Macfarlane broth was also examined. L. lactis subsp. lactis biovar diacetylactis UL719, L. lactis ATCC 11454 and P. acidilactici UL5 were able to grow and produce their bacteriocins in MRS broth and in Macfarlane broth. Each of the three candidates inhibited L. ivanovii HPB 28 and this inhibition activity was correlated with bacteriocin production. The role of bacteriocin production in the inhibition of L. ivanovii in Macfarlane broth was confirmed for P. acidilactici UL5 by using a pediocin non-producer mutant. CONCLUSIONS: The data provides some evidence that these bacteria can produce bacteriocins in a complex medium with carbon source similar to those found in the colon. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study demonstrates the capacity of lactic acid bacteria to produce their bacteriocins in a medium simulating the nutrient composition of the large intestine. © 2012The Authors Journal of Applied Microbiology © 2012 The Society for Applied Microbiology.
    Journal of Applied Microbiology 11/2012; · 2.20 Impact Factor
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    ABSTRACT: Bacteriocin production is a widespread phenomenon among bacteria. Bacteriocins hold great promise for the treatment of diseases caused by pathogenic bacteria and could be used in the future as alternatives to existing antibiotics. The anti-infective potential of bacteriocins for inhibiting pathogens has been shown in various food matrices including cheese, meat, and vegetables. However, their inhibition of pathogens in vivo remains unclear and needs more investigation, due mainly to difficulties associated with demonstrating their health benefits. Many bacteriocins produced by established or potential probiotic organisms have been evaluated as potential therapeutic agents and interesting findings have been documented in vitro as well as in a few in vivo studies. Some recent in vivo studies point to the efficacy of bacteriocin-based treatments of human and animal infections. While further investigation remains necessary before the possibilities for bacteriocins in clinical practice can be described more fully, this review provides an overview of their potential applications to human and veterinary health.
    Cellular and Molecular Life Sciences CMLS 10/2012; · 5.62 Impact Factor
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    Rima Hatoum, Steve Labrie, Ismail Fliss
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    ABSTRACT: The yeasts constitute a large and heterogeneous group of microorganisms that are currently attracting increased attention from scientists and industry. Numerous and diverse biological activities make them promising candidates for a wide range of applications not limited to the food sector. In addition to their major contribution to flavor development in fermented foods, their antagonistic activities toward undesirable bacteria, and fungi are now widely known. These activities are associated with their competitiveness for nutrients, acidification of their growth medium, their tolerance of high concentrations of ethanol, and release of antimicrobial compounds such as antifungal killer toxins or "mycocins" and antibacterial compounds. While the design of foods containing probiotics (microorganisms that confer health benefits) has focused primarily on Lactobacillus and Bifidobacterium, the yeast Saccharomyces cerevisiae var. boulardii has long been known effective for treating gastroenteritis. In this review, the antimicrobial activities of yeasts are examined. Mechanisms underlying this antagonistic activity as well as recent applications of these biologically active yeasts in both the medical and veterinary sectors are described.
    Frontiers in Microbiology 01/2012; 3:421. · 3.90 Impact Factor
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    ABSTRACT: Recently, we isolated and reported the antagonism of Paenibacillus polymyxa JB05-01-1 (P. polymyxa JB05-01-1) against Gram-negative bacteria. Here, we provide more insights and attribute the abovementioned antagonism to the production of colistins A and B, which were purified by Amberlite column exchange, C18 column hydrophobicity, superdex 75 16/60 gel filtration chromatography connected to fast protein liquid chromatography and identified by MALDI TOF/TOF, and manual nanospray analysis. The amount of colistin A and colistin B recovered from 500 ml of culture supernatant was about 0.05 mg. The specific activity and the average recovery of the eluted substances were 5,120 AU/mg and 1.1%, respectively. The minimal inhibitory concentrations of the purified colistins against Escherichia coli O157:H7 and Pseudomonas fluorescens LRC R73 were 0.13 and 0.62 μg/ml, respectively.
    Archives of Microbiology 10/2011; 194(5):363-70. · 1.91 Impact Factor
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    ABSTRACT: Bacteriocins are ribosomally-synthesized peptides or proteins produced by a wide range of bacteria. The antimicrobial activity of this group of natural substances against foodborne pathogenic and spoilage bacteria has raised considerable interest for their application in food preservation. Classifying these bacteriocins in well defined classes according to their biochemical properties is a major step towards characterizing these anti-infective peptides and understanding their mode of action. Actually, the chosen criteria for bacteriocins' classification lack consistency and coherence. So, various classification schemes of bacteriocins resulted various levels of contradiction and sorting inefficiencies leading to bacteriocins belonging to more than one class at the same time and to a general lack of classification of many bacteriocins. Establishing a coherent and adequate classification scheme for these bacteriocins is sought after by several researchers in the field. It is not straightforward to formulate an efficient classification scheme that encompasses all of the existing bacteriocins. In the light of the structural data, here we revisit the previously proposed contradictory classification and we define new structure-based sequence fingerprints that support a subdivision of the bacteriocins into 12 groups. The paper lays down a resourceful and consistent classification approach that resulted in classifying more than 70% of bacteriocins known to date and with potential to identify distinct classes for the remaining unclassified bacteriocins. Identified groups are characterized by the presence of highly conserved short amino acid motifs. Furthermore, unclassified bacteriocins are expected to form an identified group when there will be sufficient sequences.
    The Protein Journal 08/2010; 29(6):432-9. · 1.13 Impact Factor
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    ABSTRACT: To evaluate the survival of Pediococcus acidilactici UL5 and its ability to produce pediocin PA-1 during transit in an artificial gastrointestinal tract (GIT). To investigate the physicochemical and biological stability of purified pediocin PA-1 under GIT conditions. Skim milk culture of Ped. acidilactici UL5 was fed to a dynamic gastrointestinal (GI) model known as TIM-1, comprising four compartments connected by computer-controlled peristaltic valves and simulating the human stomach, duodenum, jejunum and ileum. This strain tolerated a pH of 2·7 in the gastric compartment, while lower pH reduced its viability. Bile salts in the duodenal compartment brought a further 4-log reduction after 180 min of digestion, while high viable counts (up to 5 × 10(7) CFU ml(-1) fermented milk) of Ped. acidilactici were found in both the jejunal and ileal compartments. Pediococcus acidilactici recovered from all four compartments was able to produce pediocin at the same level as unstressed cells. The activity of the purified pediocin in the gastric compartment was slightly reduced after 90 min of gastric digestion, while no detectable activity was found in the duodenal, jejunal and ileal compartments during 5 h of digestion. HPLC analysis showed partial degradation of the pediocin peptide in the duodenal compartment and massive breakdown in the jejunal and ileal compartments. Pediococcus acidilactici UL5 showed high resistance to GIT conditions, and its ability to produce pediocin was not affected, suggesting its potential as a probiotic candidate. The physicochemical and biological stability of pediocin was significantly poor under GIT conditions. Pediococcus acidilactici UL5 appears to be a potential probiotic candidate because its capacity to produce pediocin PA-1 is not affected by the GI conditions as well as the strain shows an acceptable survival rate. Meanwhile, purified pediocin PA-1 losses activity during GIT transit; microcapsules could be used to deliver it to the target site.
    Journal of Applied Microbiology 07/2010; 109(1):54-64. · 2.20 Impact Factor
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    Riadh Hammami, Ismail Fliss
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    ABSTRACT: Databases and chemo- and bioinformatics tools that contain genomic, proteomic and functional information have become indispensable for antimicrobial drug research. The combination of chemoinformatics tools, bioinformatics tools and relational databases provides means of analyzing, linking and comparing online search results. The development of computational tools feeds on a diversity of disciplines, including mathematics, statistics, computer science, information technology and molecular biology. The computational approach to antimicrobial agent discovery and design encompasses genomics, molecular simulation and dynamics, molecular docking, structural and/or functional class prediction, and quantitative structure-activity relationships. This article reviews progress in the development of computational methods, tools and databases used for organizing and extracting biological meaning from antimicrobial research.
    Drug discovery today 07/2010; 15(13-14):540-6. · 6.63 Impact Factor
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    ABSTRACT: This study was undertaken to develop new probiotic products based on liquid maple sap or its concentrate. Sap and concentrate, with or without inulin (2%) were inoculated with Bifidobacterium lactis Bb12 and Lactobacillus rhamnosus GG valio at initial counts of 10(7)-10(8)CFU/ml. Viability was assessed over four weeks of storage at 4°C and under in vitro simulated gastrointestinal conditions using dynamic gastrointestinal model known as TIM-1. Viability was maintained throughout the storage period at the same order of 10(7) to 10(8) CFU/ml. Inulin significantly enhanced the survivability during passage through the gastrointestinal tract simulator. The developed products could be an excellent alternative for delivering probiotics, especially for individuals suffering from lactose intolerance to dairy products.
    Bioresource Technology 06/2010; · 5.04 Impact Factor

Publication Stats

2k Citations
255.96 Total Impact Points


  • 1991–2014
    • Laval University
      • • Institut des Nutraceutiques et des Aliments Fonctionnels (INAF)
      • • Département des Sciences des Aliments et de Nutrition
      • • Centre de Recherche en Sciences et Technologie du Lait
      Québec, Quebec, Canada
  • 2007–2009
    • University of Tunis El Manar
      • Higher Institute of Applied Biological Sciences
      Tunis-Ville, Tūnis, Tunisia
    • ETH Zurich
      • Institute of Food, Nutrition and Health
      Zürich, ZH, Switzerland
    • Research Center for Food and Development A.C.
      Hermosillo, Sonora, Mexico
  • 1993–2009
    • Université du Québec
      Québec, Quebec, Canada
  • 2008
    • Agriculture and Agri-Food Canada
      • Lethbridge Research Centre (LRC)
      Ottawa, Ontario, Canada
  • 2002–2008
    • Alexandria University
      • Department of Dairy Science and Technology
      Al Iskandarīyah, Alexandria, Egypt
  • 2004
    • École Polytechnique Fédérale de Lausanne
      • Laboratoire de biotechnologie cellulaire
      Lausanne, VD, Switzerland
    • Eawag: Das Wasserforschungs-Institut des ETH-Bereichs
      Duebendorf, Zurich, Switzerland
  • 1993–1999
    • Centre d'enseignement et de recherche en foresterie de Sainte-Foy
      Québec, Quebec, Canada
  • 1997
    • Université du Québec à Montréal
      Montréal, Quebec, Canada
  • 1995
    • University of Manitoba
      • Department of Food Science
      Winnipeg, Manitoba, Canada