Potential probiotic Kluyveromyces marxianus fragilis B0399 modulates the immune response in Caco-2 cells and PBMCs and impacts on the human gut microbiota in an in vitro colonic model system.
Considering the increase in the consumption of yeasts as human probiotics, the aim of this study was to broadly... more Considering the increase in the consumption of yeasts as human probiotics, the aim of this study was to broadly investigate the beneficial properties of the lactic yeast K. marxianus fragilis B0399. Several potential probiotic traits of K. marxianus fragilis B0399 were investigated using in vitro assays, including adhesion and immune modulation, as well as the effect of the administration of 10(7) CFU/day of K. marxianus fragilis B0399 on composition and metabolic activity of the human intestinal microbiota in a 3-stage continuous culture system simulating the human colon.We demonstrated that this strain was highly adhesive to the human enterocyte-like Caco-2 cells and modulated the immune response, inducing pro-inflammatory cytokines in peripheral blood mononuclear cells (PBMCs). In presence of inflammatory stimulation with LPS, K. marxianus fragilis B0399 provoked a decrease in the production of pro-inflammatory cytokines in PBMCs and Caco-2 cells, thus ameliorating the inflammatory response.Furthermore, K. marxianus fragilis B0399 impacted on the colonic microbiota, increasing the bifidobacterial concentration in the stages of the colonic model system simulating the proximal and transverse colon. Short chain fatty acids acetate and propionate also increased following the yeast supplementation. Finally, K. marxianus fragilis B0399 was found to induce a decrease of the cytotoxic potential of the cultural supernatant from the first stage of the colonic model system.The effects of K. marxianus fragilis B0399 on adhesion, immune function and colonic microbiota demonstrate that this strain possesses a number of beneficial and strain-specific properties desirable in a microorganism considered for application as a probiotics.
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Download (.pdf) Functional intestinal microbiome, new frontiers in prebiotic design
In this review we focus on the revision of the prebiotic concept in the context of the new metagenomic era. Functional... more In this review we focus on the revision of the prebiotic concept in the context of the new metagenomic era. Functional metagenomic data provided by the Human Microbiome Project are revolutionizing the view of the symbiotic relationship between the intestinal microbiota and the human host. A deeper knowledge of the mechanisms that govern the dynamic interplay between diet, intestinal microbiota and host nutrition opens the way to better information on the prebiotic structure-function relationships, tailoring prebiotic formula into specific health attributes. On the other hand, functional genomic studies of the sourdough microbial communities allow to scan the environmental variability to identify novel metabolic traits for the biosynthesis of new potential prebiotic molecules. The integration of the functional analyses provided by the massive sequencing of bacterial genomes and metagenomes will allow the rational production of a desired prebiotic molecule with specific functional properties.
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In silico identification of pathogenic strains of Cronobacter from biochemical data reveals association of inositol fermentation with pathogenicity
BMC Microbiology, 2011
We demonstrated a computational approach allowing existing diagnostic kits to be used to identify pathogenic strains... more
We demonstrated a computational approach allowing existing diagnostic kits to be used to identify pathogenic strains of Cronobacter. The resulting clusters correlated well with MLST sequence types and revealed new information about the pathogenicity of Cronobacter species.
Comment: This paper overlaps with our CDC's Emerging Infectious Disease paper on the cloncal nature of meningitic C. sakazakii ST4.
Combined effects of aqueous chlorine dioxide and ultrasonic treatments on postharvest storage quality of plum fruit (Prunus salicina L.)
by Zhao Chen
The individual and combined effects of aqueous chlorine dioxide (40mg L−1 ClO2 for 10min) and ultrasonic (100W... more The individual and combined effects of aqueous chlorine dioxide (40mg L−1 ClO2 for 10min) and ultrasonic (100W ultrasound for 10min) treatments on postharvest storage quality of plum fruit (Prunus salicina L.) were investigated. Two combination modes of these two treatments, treatment with ClO2 solution accompanied by simultaneous ultrasonic waves (one-step mode) and applying them sequentially (two-stepmode)were adopted. The effect of combined treatments onmaintaining contents of total flavonoids, ascorbic acid, reducing sugars, and titratable acidswere similar butweremore beneficial than the individual treatments and the untreated control. The one-step mode was more effective in reducing the initial microflora and retaining sensory qualities of plum fruit than the two-step mode, and fruit shelf-life could be extended to 60 d compared to 35 d for the control.Moreover, therewere no detectable chemical residues in the treated samples with the one-step mode. These results demonstrated that the combined treatments of ClO2 and ultrasound could be a promising approach to maintain postharvest storage quality of plum fruit without significant risks to consumers.
Effects of aqueous chlorine dioxide treatment on nutritional components and shelf-life of mulberry fruit (Morus alba L.)
by Zhao Chen
Effects of aqueous chlorine dioxide (ClO2) treatment on nutritional components and shelf-life of mulberry fruit (Morus... more Effects of aqueous chlorine dioxide (ClO2) treatment on nutritional components and shelf-life of mulberry fruit (Morus alba L.) were investigated. Mulberry fruit were immersed into 20, 60, and 80 mg/L ClO2 solutions for 5, 10, and 15 min, respectively. Mulberries were then rinsed with potable tap water for 1 min and stored at -1 ºC for 14 d. ClO2 treatment was effective in retention of flavonoid, ascorbic acid, reducing sugar, and titratable acid. ClO2 concentration and treatment time were significant factors affecting ClO2 treatment. The shelf-life of the samples treated by 60 mg/L ClO2 for 15 min was extended to 14 d compared to 8 d for the control. No ClO2, ClO2-, or ClO3- residues were detected in samples treated by 60 mg/L ClO2 for 15 min. These results indicated that ClO2 treatment was a promising approach to preserve mulberry fruit with no significant risks of chemical residues.
Effects of aqueous chlorine dioxide treatment on enzymatic browning and shelf-life of fresh-cut asparagus lettuce (Lactuca sativa L.)
by Zhao Chen
Effects of aqueous chlorine dioxide (ClO2) treatment on enzymatic browning and shelf-life of fresh-cut asparagus... more Effects of aqueous chlorine dioxide (ClO2) treatment on enzymatic browning and shelf-life of fresh-cut asparagus lettuce (Lactuca sativa L. var. angustana) were investigated. Fresh-cut asparagus lettuce was treated at different concentrations (10, 40, and 100 mg L-1) for different times (5, 10, and 20 min). Following treatments, lettuce slices were stored at 4 ℃ for 14 days. The activities of polyphenol oxidase (PPO) and peroxidase (POD) in the lettuce were reduced by ClO2. Meanwhile, the degradation of color in the ClO2 treated lettuce was also delayed. It was concluded that ClO2 concentration and treatment time were two significant factors affecting ClO2 treatment on enzymatic browning of fresh-cut asparagus lettuce (P < 0.05). From the microbiological and sensory quality perspectives, the treatment with 100 mg L-1 ClO2 for 20 min could prolong the shelf-life to 14 days compared to 4 days for the control. These results indicated that ClO2 treatment was a promising approach to inhibit enzymatic browning and prolong shelf-life of fresh-cut asparagus lettuce.
Modelling inactivation by aqueous chlorine dioxide of Dothiorella gregaria Sacc. and Fusarium tricinctum (Corda) Sacc. spores inoculated on fresh chestnut kernel
by Zhao Chen
Aims: To model survival curves of Dothiorella gregaria Sacc. and Fusarium tricinctum (Corda) Sacc. spores inoculated... more
Aims: To model survival curves of Dothiorella gregaria Sacc. and Fusarium tricinctum (Corda) Sacc. spores inoculated on fresh chestnut kernel exposed to aqueous chlorine dioxide (ClO2).
Methods and Results: Spores of two dominant spoilage fungi, D. gregaria andF. tricinctum, were inoculated onto chestnut kernel and treated with ClO2. The inactivation efficacy of ClO2 treatment increased with ClO2 concentration and treatment time. The Weibull model was the best model to describe the ClO2 survival curves of D. gregaria, while the modified Gompertz model was most appropriate for fitting the survival curves of F. tricinctum. Within the range of ClO2 concentration from 3 to 7 mg l-1, the n values in the Weibull model were similar. The b value in the Weibull model and decimal logarithms of the M, B and C values in the modified Gompertz model had linear relationships with ClO2 concentration. After simplification, these two models still provided acceptable predictions.
Conclusion: Applying models for describing survival curves of fungal spores on chestnut kernel by aqueous ClO2 was feasible.
Significance and Impact of the Study: This work would promote the application of ClO2 sanitizing technique and mathematical models when preventingthe occurrence of chestnut kernel decay.
Growth and survival of Cronobacter species as measured by media performance
Recovery of Cronobacter after heat treatment is important for determining how effective control measures are.
Abstract: Cronobacter sakazakii is an emerging food borne pathogen which has been associated with outbreaks of a rare... more
Abstract: Cronobacter sakazakii is an emerging food borne pathogen which has been associated with outbreaks of a rare form of infant meningitis. Although the origin of the microorganism has not been established, several infection cases have been associated with the consumption of contaminated powdered infant formula (PIF).
In the present study, growth characteristics of three C. sakazakii strains isolated from PIF samples and C. muytjensii strain ATCC 51329, which was formerly the ATCC Preceptrol™ strain for the quality control of ‘Enterobacter sakazakii’ prior to the taxonomic revision, were investigated in Tryptone Soya broth (TSB) and reconstituted PIF at 4, 10, 25, 37, 45 and 50ºC. The viability of heat treated cells of Cronobacter strains was evaluated by plating on Violet Red Bile Glucose agar (VRBGA) and the Druggan-Forsythe-Iversen (DFI) chromogenic agar followed by incubation at 37ºC. These strains were also subjected to higher temperatures between 52 to 6 ºC to measure their thermal tolerance. The mean generation time of all Cronobacter strains were slightly lower in PIF than in TSB. C. muytjensii ATCC 51329 showed lower generation time in all culture media and all temperatures compared to the Cronobacter food isolates, but the results were not significantly different (P>0.05). The results also indicated that combination of PIF: DFI culture media had higher recovery at all temperatures compared to other combinations. Survival study also indicated that C. muytjensii ATCC 51329 had higher D-value compared to food isolates at all incubation temperatures.
