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Denis Roy

Université Laval, Food Sciences, Faculty Member

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Denis Roy is Full Professor with the Department of Food Sciences of the Université Laval (Quebec, Canada). He is an expert in the field of probiotics and prebiotics and former Tier I holder of the Canada Research Chair in Lactic Culture Biotechnology for Dairy and Probiotic Industries (2003-2017). His research interests focuses on functional food- and colon-related microbial cultures, with attention to their functioning, properties, and potential health benefits. Molecular approaches such as metagenomics and metatranscriptomics are applied to define the diversity and to measure the gene expression of microbial communities found in the intestinal tract of animal and human or in food systems.

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Papers by Denis Roy

Comprehensive analysis of the metabolic and genomic features of tannin-transforming Lactiplantibacillus plantarum strains

Scientific Reports

Extracellular tannase Lactiplantibacillus plantarum-producing strains (TanA+) release bioactive m... more Extracellular tannase Lactiplantibacillus plantarum-producing strains (TanA+) release bioactive metabolites from dietary tannins. However, there is a paucity of knowledge of TanA+ strains and their hydrolyzing capacities. This study aimed to shed light on the metabolic and genomic features of TanA+ L. plantarum strains and to develop a screening technique. The established spectrophotometric was validated by UPLC-UV-QToF. Eight of 115 screened strains harbored the tanA gene, and six presented TanA activity (PROBI S126, PROBI S204, RKG 1-473, RKG 1-500, RKG 2-219, and RKG 2-690). When cultured with tannic acid (a gallotannin), TanA+ strains released 3.2−11 times more gallic acid than a lacking strain (WCFS1) (p < 0.05). TanA+ strains with gallate decarboxylase (n = 5) transformed this latter metabolite, producing 2.2–4.8 times more pyrogallol than the TanA lacking strain (p < 0.05). However, TanA+ strains could not transform punicalagin (an ellagitannin). Genomic analysis reveal...

Effects of Daily Raspberry Consumption on Immune-Metabolic Health in Subjects at Risk of Metabolic Syndrome: A Randomized Controlled Trial

Nutrients

Consumption of red raspberries has been reported to exert acute beneficial effects on postprandia... more Consumption of red raspberries has been reported to exert acute beneficial effects on postprandial glycemia, insulinemia, triglyceridemia, and cytokine levels in metabolically disturbed subjects. In a two-arm parallel-group, randomized, controlled trial, 59 subjects with overweight or abdominal obesity and with slight hyperinsulinemia or hypertriglyceridemia were randomized to consume 280 g/day of frozen raspberries or to maintain their usual diet for 8 weeks. Primary analyses measured metabolic differences between the groups. Secondary analyses performed with omics tools in the intervention group assessed blood gene expression and plasma metabolomic changes following the raspberry supplementation. The intervention did not significantly affect plasma insulin, glucose, inflammatory marker concentrations, nor blood pressure. Following the supplementation, 43 genes were differentially expressed, and several functional pathways were enriched, a major portion of which were involved in th...

Optimization of Preservation Methods Allows Deeper Insights into Changes of Raw Milk Microbiota

Microorganisms

The temporal instability of raw milk microbiota drastically affects the reliability of microbiome... more The temporal instability of raw milk microbiota drastically affects the reliability of microbiome studies. However, little is known about the microbial integrity in preserved samples. Raw cow milk samples were preserved with azidiol or bronopol and stored at 4 °C, or with dimethyl sulfoxide (DMSO) or a mixture of azidiol and DMSO and stored at −20 °C for up to 30 days. Aliquots of 5-, 10-, and 30-day post-storage were treated with propidium monoazide (PMA), then analyzed by sequencing the 16S rRNA gene V3-V4 and V6-V8 regions. The V6-V8 gave a higher richness and lower diversity than the V3-V4 region. After 5-day storage at 4 °C, the microbiota of unpreserved samples was characterized by a drastic decrease in diversity, and a significant shift in community structure. The treatment with azidiol and DMSO conferred the best community stabilization in preserved raw milk. Interestingly, the azidiol treatment performed as well for up to 10 days, thus appearing as a suitable alternative. H...

Enhanced Exopolysaccharide Production by Lactobacillus rhamnosus in Co-Culture with Saccharomyces cerevisiae

Applied Sciences

Lactobacillus strains are known to produce exopolysaccharides (EPS) with recognized health benefi... more Lactobacillus strains are known to produce exopolysaccharides (EPS) with recognized health benefits (i.e. prebiotic and immunomodulation) but production is limited by low yields. Co-culture has been shown to improve metabolite productivity, particularly bacteriocins and EPS. Although lactic acid bacteria (LAB) and yeasts are found in several fermented products, the molecular mechanisms linked to the microbial interactions and their influences on EPS biosynthesis are unclear. The aim of the present study was to investigate the effect of co-culture on EPS production by three Lactobacillus rhamnosus strains (ATCC 9595, R0011, and RW-9595M) in association with Saccharomyces cerevisiae. Fermentation, in both mono and co-culture, was carried out and the expression of key LAB genes was monitored. After 48 h, results revealed that EPS production was enhanced by 39%, 49%, and 42% in co-culture for R0011, ATCC 9595, and RW-9595M, respectively. Each strain showed distinctive gene expression pr...

Apple peel polyphenols reduce mitochondrial dysfunction in mice with DSS-induced ulcerative colitis

The Journal of nutritional biochemistry, Jan 21, 2018

Inflammatory bowel diseases (IBDs) are multifaceted and relapsing immune disorders, which necessi... more Inflammatory bowel diseases (IBDs) are multifaceted and relapsing immune disorders, which necessitate long-term dependence on powerful drugs. As the use of natural product-based therapies has emerged as a promising intervention, the present study aimed to further characterize dried apple peel powder (DAPP) mechanisms of action and evaluate the preventive and curative effects of DAPP on mitochondrial functions in a murine model. Induction of intestinal inflammation in mice is performed by oral administration of the dextran sodium sulfate (DSS) at 2.5% for 10 days. Doses of DAPP (200 or 400 mg/kg/day) were administered by gavage for 10 days pre- and 1 day after colitis induction simultaneously with DSS treatment for a period of 10 days. The preventive (200 mg/kg/day) and therapeutic (400 mg/kg/day) doses of DAPP limited DSS-induced histological lesions, improved macroscopic parameters and attenuated clinical signs. DAPP at the same conditions reduced massive infiltration of inflammato...

Arctic berry extracts target the gut-liver axis to alleviate metabolic endotoxaemia, insulin resistance and hepatic steatosis in diet-induced obese mice

Diabetologia, Jan 21, 2017

There is growing evidence that fruit polyphenols exert beneficial effects on the metabolic syndro... more There is growing evidence that fruit polyphenols exert beneficial effects on the metabolic syndrome, but the underlying mechanisms remain poorly understood. In the present study, we aimed to analyse the effects of polyphenolic extracts from five types of Arctic berries in a model of diet-induced obesity. Male C57BL/6 J mice were fed a high-fat/high-sucrose (HFHS) diet and orally treated with extracts of bog blueberry (BBE), cloudberry (CLE), crowberry (CRE), alpine bearberry (ABE), lingonberry (LGE) or vehicle (HFHS) for 8 weeks. An additional group of standard-chow-fed, vehicle-treated mice was included as a reference control for diet-induced obesity. OGTTs and insulin tolerance tests were conducted, and both plasma insulin and C-peptide were assessed throughout the OGTT. Quantitative PCR, western blot analysis and ELISAs were used to assess enterohepatic immunometabolic features. Faecal DNA was extracted and 16S rRNA gene-based analysis was used to profile the gut microbiota. Trea...

A polyphenol-rich cranberry extract reverses insulin resistance and hepatic steatosis independently of body weight loss

Molecular metabolism, 2017

Previous studies have reported that polyphenol-rich extracts from various sources can prevent obe... more Previous studies have reported that polyphenol-rich extracts from various sources can prevent obesity and associated gastro-hepatic and metabolic disorders in diet-induced obese (DIO) mice. However, whether such extracts can reverse obesity-linked metabolic alterations remains unknown. In the present study, we aimed to investigate the potential of a polyphenol-rich extract from cranberry (CE) to reverse obesity and associated metabolic disorders in DIO-mice. Mice were pre-fed either a Chow or a High Fat-High Sucrose (HFHS) diet for 13 weeks to induce obesity and then treated either with CE (200 mg/kg, Chow + CE, HFHS + CE) or vehicle (Chow, HFHS) for 8 additional weeks. CE did not reverse weight gain or fat mass accretion in Chow- or HFHS-fed mice. However, HFHS + CE fully reversed hepatic steatosis and this was linked to upregulation of genes involved in lipid catabolism (e.g., PPARα) and downregulation of several pro-inflammatory genes (eg, COX2, TNFα) in the liver. These findings...

The Clinical and Economic Impact of Probiotics Consumption on Respiratory Tract Infections: Projections for Canada

PLOS ONE, 2016

Introduction There is accumulating evidence supporting the use of probiotics, which are defined a... more Introduction There is accumulating evidence supporting the use of probiotics, which are defined as "live microorganisms which, when administered in adequate amounts, confer a health benefit on the host", as a preventive measure against respiratory tract infections (RTI). Two recent metaanalyses showed probiotic consumption (daily intake of 10 7 to 10 10 CFU in any form for up to 3 months) significantly reduced RTI duration, frequency, antibiotic use and work absenteeism. Objectives The aim of this study was to assess the impact of probiotic use in terms of number of RTI episodes and days averted, and the number of antibiotic prescriptions and missed workdays averted, in the general population of Canada. In addition, the corresponding economic impact from both a healthcare payer and a productivity perspective was estimated.

Apple peel polyphenols: A key player in the prevention and treatment of experimental inflammatory bowel disease

Clinical science (London, England : 1979), Dec 14, 2016

Diets rich in fruits and vegetables may reduce oxidative stress and inflammation via several mech... more Diets rich in fruits and vegetables may reduce oxidative stress and inflammation via several mechanisms. These beneficial effects may be due to their high polyphenol content. The aims of the present study are to evaluate the preventive and therapeutic aspects of polyphenols in dried apple peel extract (DAPP) on intestinal inflammation while elucidating the underlying mechanisms and clinical benefits. Induction of intestinal inflammation in mice was performed by oral administration of the inflammatory agent DSS at 2.5% for 10 days. Physiological and supraphysiological doses of DAPP (200 and 400 mg/kg/day, respectively) were administered by gavage for 10 days pre- and post-DSS treatment. DSS-mediated inflammation caused weight loss, shortening of the colon, dystrophic detachment of the epithelium, and infiltration of mono- and polymorphonuclear cells in the colon. DSS induced an increase in lipid peroxidation, a down-regulation of antioxidants, an augmented MPO and COX2, an elevated P...

TriggeringAkkermansiawith dietary polyphenols: A new weapon to combat the metabolic syndrome?

Gut Microbes, 2016

The gut and its bacterial colonizers are now well characterized as key players in whole-body meta... more The gut and its bacterial colonizers are now well characterized as key players in whole-body metabolism, opening new avenues of research and generating great expectation for new treatments against obesity and its cardiometabolic complications. As diet is the main environmental factor affecting the gut microbiota, it has been suggested that fruits and vegetables, whose consumption is strongly associated with a healthy lifestyle, may carry phytochemicals that could help maintain intestinal homeostasis and metabolic health. We recently demonstrated that oral administration of a cranberry extract rich in polyphenols prevented diet-induced obesity and several detrimental features of the metabolic syndrome in association with a remarkable increase in the abundance of the mucin-degrading bacterium Akkermansia in the gut microbiota of mice. This addendum provides an extended discussion in light of recent discoveries suggesting a mechanistic link between polyphenols and Akkermansia, also contemplating how this unique microorganism may be exploited to fight the metabolic syndrome.

Mutual cross-feeding interactions between Bifidobacterium longum NCC2705 and Eubacterium rectale ATCC 33656 explain the bifidogenic and butyrogenic effects of arabinoxylan-oligosaccharides

Applied and Environmental Microbiology, 2015

Arabinoxylan oligosaccharides (AXOS) are a promising class of prebiotics that have the potential ... more Arabinoxylan oligosaccharides (AXOS) are a promising class of prebiotics that have the potential to stimulate the growth of bifidobacteria and the production of butyrate in the human colon, known as the bifidogenic and butyrogenic effects, respectively. Although these dual effects of AXOS are considered beneficial for human health, their underlying mechanisms are still far from being understood. Therefore, this study investigated the metabolic interactions betweenBifidobacterium longumsubsp.longumNCC2705 (B. longumNCC2705), an acetate producer and arabinose substituent degrader of AXOS, andEubacterium rectaleATCC 33656, an acetate-converting butyrate producer. Both strains belong to prevalent species of the human colon microbiota. The strains were grown on AXOS during mono- and coculture fermentations, and their growth, AXOS consumption, metabolite production, and expression of key genes were monitored. The results showed that the growth of both strains and gene expression in both s...

Probiotics as Complementary Treatment for Metabolic Disorders

Diabetes & Metabolism Journal, 2015

Over the past decade, growing evidence has established the gut microbiota as one of the most impo... more Over the past decade, growing evidence has established the gut microbiota as one of the most important determinants of metabolic disorders such as obesity and type 2 diabetes. Indeed, obesogenic diet can drastically alter bacterial populations (i.e., dysbiosis) leading to activation of pro-inflammatory mechanisms and metabolic endotoxemia, therefore promoting insulin resistance and cardiometabolic disorders. To counteract these deleterious effects, probiotic strains have been developed with the aim of reshaping the microbiome to improve gut health. In this review, we focus on benefits of widely used probiotics describing their potential mechanisms of action, especially their ability to decrease metabolic endotoxemia by restoring the disrupted intestinal mucosal barrier. We also discuss the perspective of using new bacterial strains such as butyrate-producing bacteria and the mucolytic Akkermansia muciniphila, as well as the use of prebiotics to enhance the functionality of probiotics. Finally, this review introduces the notion of genetically engineered bacterial strains specifically developed to deliver anti-inflammatory molecules to the gut.

Modulatory effects of a cranberry extract co-supplementation with Bacillus subtilis CU1 probiotic on phenolic compounds bioavailability and gut microbiota composition in high-fat diet-fed mice

PharmaNutrition, 2015

ABSTRACT Cranberry consumption has been demonstrated to improve features of the metabolic syndrom... more ABSTRACT Cranberry consumption has been demonstrated to improve features of the metabolic syndrome, therefore providing an alternative strategy to prevent obesity and type-2 diabetes. Moreover, gut dysbiosis is now considered as a key factor in metabolic disorders. In order to understand the involvement of phenolic compounds in the health-improving effects of cranberry, this study aimed to investigate their bioavailability after oral administration of a cranberry extract (CE) to high-fat high-sucrose (HFHS) fed mice, and to explore a possible modulation of gut microbiota composition following a co-supplementation with spores of Bacillus subtilis CU1 probiotic (CE/P). Phenolic metabolites were extracted and characterized from plasma using μSPE-UHPLC-MS/MS, and a metagenomic analysis was performed on feces to assess gut bacterial composition. 22 circulating metabolites were identified, mainly microbial degradation products of native cranberry phenolic compounds. Plasma concentration of 3 microbial metabolites was significantly increased with the CE/P co-treatment: p-coumaric acid, m-coumaric acid and p-hydroxybenzoic acid (+ 53%, + 103% and + 70% respectively). Associated to this modulation, we reported significant differences in the proportion of Barnesiella and Oscillibacter genera in CE/P treated mice in comparison with control animals. This study thus highlights the impact of an altered gut microbiota on phenolic compounds degradation and bioavailability in mice.

Bioluminescence assay for estimating the hydrophobic properties of bacteria as revealed by hydrophobic interaction chromatography

Applied and environmental microbiology, 1991

The luciferin-luciferase bioluminescence method was used to estimate the number of bacteria retai... more The luciferin-luciferase bioluminescence method was used to estimate the number of bacteria retained in neutral and amphiphilic gels and those in the eluate to determine the hydrophobic surface properties of bacteria by using hydrophobic interaction chromatography. Good correlations were found between viable counts and ATP content for Escherichia coli, Pseudomonas fragi, and Listeria monocytogenes. ATP determination was more rapid than viable counts for characterizing the relative hydrophobicity of L. monocytogenes. Quantitative estimations of adsorption of L. monocytogenes on octyl-Sepharose indicate that this microorganism is hydrophilic.

Biofilm formation and biocides sensitivity of Pseudomonas marginalis isolated from a maple sap collection system

Journal of food protection, 2006

The susceptibility of planktonic and biofilm cells of Pseudomonas marginalis toward four commonly... more The susceptibility of planktonic and biofilm cells of Pseudomonas marginalis toward four commonly used biocides at different temperatures (15 and 30 degrees C) and biofilm growth times (24 and 48 h) was assessed. Using the MBEC biofilm device, biofilm production in maple sap was shown to be highly reproducible for each set of conditions tested. Biofilm formation was influenced by growth temperature and time. A temperature of 15 degrees C and incubation time of 24 h yielded fewer CFU per peg and showed fewer adhered cells and typical biofilm structures, based on scanning electron microscopy observations as compared with other conditions. Minimal biofilm eradication concentration values for P. marginalis were significantly greater (P. < 0.001) than were MBCs for planktonic cells and for every biocide tested, with the exception of minimal biofilm eradication concentration values for peracetic acid at 15 degrees C and 24 h. Sodium hypochlorite and peracetic acid sanitizers were able ...

$Research paper thumbnail of Comparison of bifidobacterial growth-promoting activity of ultrafiltered casein hydrolyzate fractions$

Comparison of bifidobacterial growth-promoting activity of ultrafiltered casein hydrolyzate fractions

Le Lait, 1994

HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific re... more HAL is a multidisciplinary open access archive for the deposit and dissemination of scientific research documents, whether they are published or not. The documents may come from teaching and research institutions in France or abroad, or from public or private research centers. L'archive ouverte pluridisciplinaire HAL, est destinée au dépôt et à la diffusion de documents scientifiques de niveau recherche, publiés ou non, émanant des établissements d'enseignement et de recherche français ou étrangers, des laboratoires publics ou privés.

Utilisation d'hydrolysats enzymatiques de caséine pour la croissance des bifidobactéries

Le Lait, 1992

département des sciences et technologie des aliments, centre de recherche en sciences et technolo... more département des sciences et technologie des aliments, centre de recherche en sciences et technologie du lait, Ste-Foy, Québec, G 1K 7P4; Bifidobacterium sp 1 hydrolysat de caséine 1 ultrafiltration 1 effet stimulant Summary-Effect of casein hydrolysates on the growth of bifidobacteria. The growthpromotional activity of casein hydrolysa tes was tested for 5 species of the genus Bifidobacterium. AIcalase, chymotrypsin and trypsin were used to produce the casein hydrolysates which had been separated by ultrafiltration on a hollow fiber membrane (molecular weight eut-off: 30 000 Da). Comparison of 3 semi-synthetic or synthetic media for cultivation of bifidobacteria indicated that peptides might be a preferable source of nitrogen to free amino acids. Garches and Norris media were selected to compare the efficiency of the different ultrafiltered hydrolysa tes to a mix of free amino acids (Garches) and to a commercial casein hydrolysa te (Norris). After 48 h of growth, no difference appeared in terms of acidity between the ultrafiltered hydrolysa tes for the species Bifidobacterium bifi-• Correspondance •• Tirés à part 394 M Proulx et al dum var pennsylvanicus and Bifidobacterium adolescentis. Bifidobacterium infantis showed a large f1exibi/ity regarding nitrogen requirement. In Garches medium, significant growth-promotional activity was obtained for the species Bifidobacterium breve and Bifidobacterium longum. In general, in the Norris medium commercial hydrolysa te (N-Z Case) allows better growth of the 5 bacterial species tested than ultrafiltered hydrolysa tes. A stimulating effect may be observed with ultrafiltered hydrolysa tes during growth ofB infantis and B breve. Bifidobacterium sp / casein hydrolysate / ultrafiltration / growth enhancing factor

Biochemical characteristics of fermented milk produced by mixed-cultures of lactic starters and bifidobacteria

Le Lait, 2000

Strains of bifidobacteria of human origin (Bifidobacterium bifidum, B. breve, B. infantis and B. ... more Strains of bifidobacteria of human origin (Bifidobacterium bifidum, B. breve, B. infantis and B. longum) were inoculated simultaneously with mixed cultures of lactococci, citratefermenting lactococci and leuconostocs to determine their impact on biochemical characteristics of fermented dairy products. Fermentations were carried out under different conditions of temperature, milk protein concentration and ratio of acidifying/aromatic lactic acid bacteria. The survival or growth of bifidobacteria during production of fermented milk was not affected by the presence of lactic starters. On the other hand, the presence of bifidobacteria during the production of fermented milk did not influence the growth of total lactococci, citrate-fermenting lactococci and leuconostocs. The variation of the milk protein content did not modify the growth of bifidobacteria and mixed-cultures of lactic starters. However, the presence of bifidobacteria changed the final characteristic of the fermented milk. Residual lactose in fermented milks containing B. breve, B. bifidum and B. infantis was lower than that found in fermented milks without bifidobacteria and those containing B. longum. The fermented milks without bifidobacteria contained less acetaldehyde than those containing bifidobacteria whereas the concentration of diacetyl was less important in the presence of bifidobacteria. However, the ethanol concentration increased when bifidobacteria were used with mixed cultures of lactococci, citrate-fermenting lactococci and leuconostocs. A temperature of 35 °C seems to be desirable because it allows the growth of bifidobacteria without affecting in a drastic way the growth and activity of leuconostocs and other lactic starters. bifidobacteria / starter / leuconostoc / fermented milk / volatile compound Résumé-Les caractéristiques biochimiques du lait fermenté par des cultures mixtes de ferments lactiques et de bifidobactéries. Des souches de bifidobactéries d'origine humaine (Bifidobacterium breve, B. longum, B. infantis et B. bifidum) ont été inoculées simultanément avec des cultures mixtes de lactocoques acidifiants, des lactocoques aromatiques et de leuconostocs afin

Evaluation of bacterial diversity in the gut of piglets supplemented with probiotics using ribosomal intergenic spacer analysis

Canadian Journal of Animal Science, 2007

In this study, ribosomal intergenic spacer analysis (RISA) was used to monitor changes of intesti... more In this study, ribosomal intergenic spacer analysis (RISA) was used to monitor changes of intestinal microbiota of piglets treated at birth with or without Pediococcus acidilactici (PA) and/or Saccharomyces cerevisiae ssp. boulardii (SCB) and weaned piglets fed with control diet supplemented with PA and/or SCB or antibiotic. During lactation, probiotics were given orally to piglets three times a week. At weaning (day 21), probiotics and the antibiotic, tiamulin, were added to the diet. Fifteen piglets per treatment were slaughtered at day 18 and day 24. The tracking of each probiotic from colonic samples was done using PCR primers specific for PA targeting the 16S rRNA gene or a specific culture medium for enumeration of SCB. The results showed the presence of probiotics in colonic samples of piglets supplemented with probiotics. Dendograms (UPGMA and Ward’s method), and non-metric multidimensional scaling analysis showed that the variability of RISA profiles in colonic microflora b...

Immunomodulatory effects of probiotics in the intestinal tract

Current issues in molecular biology, 2008

The intestinal microbiota is the largest source of microbial stimulation that exerts both harmful... more The intestinal microbiota is the largest source of microbial stimulation that exerts both harmful and beneficial effects on human health. The interaction between probiotic and enterocytes is the initiating event in immunomodulation and merits particular attention. The effects of probiotic is strain dependent and for each new probiotic strain, profiles of cytokines secreted by lymphocytes, enterocytes or dendritic cells that come in contact with the strain should be systematically established. To evaluate the effects of probiotics on the immune system, models that mimic the mucosa, and thus the physiological reality, should be preferred whenever it is possible. Then, the in vitro observed effects should be backed up by properly conducted randomized double bind clinical studies. More detailed studies are needed to determine the precise action mode of probiotics on both mucosal and systemic immunity.