Publications by authors named "Kalliopi Rantsiou"

88 Publications

Specific metagenomic asset drives the spontaneous fermentation of Italian sausages.

Food Res Int 2021 Jun 29;144:110379. Epub 2021 Apr 29.

Department of Agricultural, Forest, and Food Sciences, University of Turin, Largo Paolo Braccini 2, 10095, Grugliasco, Torino, Italy. Electronic address:

Metagenomics is a powerful tool to study and understand the microbial dynamics that occur during food fermentation and allows to close the link between microbial diversity and final sensory characteristics. Each food matrix can be colonized by different microbes, but also by different strains of the same species. In this study, using an innovative integrated approach combining culture-dependent method with a shotgun sequencing, we were able to show how strain-level biodiversity could influence the quality characteristics of the final product. The attention was placed on a model food fermentation process: Salame Piemonte, a Protected Geographical Indication (PGI) Italian fermented sausage. Three independent batches produced in February, March and May 2018 were analysed. The sausages were manufactured, following the production specification, in a local meat factory in the area of Turin (Italy) without the use of starter cultures. A pangenomic approach was applied in order to identify and evaluate the lactic acid bacteria (LAB) population driving the fermentation process. It was observed that all batches were characterized by the presence of few LAB species, namely Pediococcus pentosaceus, Latilactobacillus curvatus and Latilactobacillus sakei. Sausages from the different batches were different when the volatilome was taken into consideration, and a strong association between quality attributes and strains present was determined. In particular, different strains of L. sakei, showing heterogeneity at genomic level, colonized the meat at the beginning of each production and deeply influenced the fermentation process by distinctive metabolic pathways that affected the fermentation process and the final sensory aspects.
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http://dx.doi.org/10.1016/j.foodres.2021.110379DOI Listing
June 2021

Functional pangenome analysis reveals high virulence plasticity of Aliarcobacter butzleri and affinity to human mucus.

Genomics 2021 May 4;113(4):2065-2076. Epub 2021 May 4.

Department of Agricultural, Forest and Food Sciences (DISAFA), University of Turin, Italy. Electronic address:

Aliarcobacter butzleri is an emerging pathogen that may cause enteritis in humans, however, the incidence of disease caused by this member of the Campylobacteriaceae family is still underestimated. Furthermore, little is known about the precise virulence mechanism and behavior during infection. Therefore, in the present study, through complementary use of comparative genomics and physiological tests on human gut models, we sought to elucidate the genetic background of a set of 32 A. butzleri strains of diverse origin and to explore the correlation with the ability to colonize and invade human intestinal cells in vitro. The simulated infection of human intestinal models showed a higher colonization rate in presence of mucus-producing cells. For some strains, human mucus significantly improved the resistance to physical removal from the in vitro mucosa, while short time-frame growth was even observed. Pangenome analysis highlighted a hypervariable accessory genome, not strictly correlated to the isolation source. Likewise, the strain phylogeny was unrelated to their shared origin, despite a certain degree of segregation was observed among strains isolated from different segments of the intestinal tract of pigs. The putative virulence genes detected in all strains were mostly encompassed in the accessory fraction of the pangenome. The LPS biosynthesis and in particular the chain glycosylation of the O-antigen is harbored in a region of high plasticity of the pangenome, which would indicate frequent horizontal gene transfer phenomena, as well as the involvement of this hypervariable structure in the adaptive behavior and sympatric evolution of A. butzleri. Results of the present study deepen the current knowledge on A. butzleri pangenome by extending the pool of genes regarded as virulence markers and provide bases to develop new diagnostic approaches for the detection of those strains with a higher virulence potential.
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http://dx.doi.org/10.1016/j.ygeno.2021.05.001DOI Listing
May 2021

Unravelling the Molecular Mechanisms Underlying the Protective Effect of Lactate on the High-Pressure Resistance of .

Biomolecules 2021 Apr 30;11(5). Epub 2021 Apr 30.

Department of Agricultural, Forest, and Food Science, University of Turin, Grugliasco 10095, Turin, Italy.

Formulations with lactate as an antimicrobial and high-pressure processing (HPP) as a lethal treatment are combined strategies used to control in cooked meat products. Previous studies have shown that when HPP is applied in products with lactate, the inactivation of is lower than that without lactate. The purpose of the present work was to identify the molecular mechanisms underlying the piezo-protection effect of lactate. Two strains (CTC1034 and EGDe) were independently inoculated in a cooked ham model medium without and with 2.8% potassium lactate. Samples were pressurized at 400 MPa for 10 min at 10 °C. Samples were subjected to RNA extraction, and a shotgun transcriptome sequencing was performed. The short exposure of cells to lactate through its inoculation in a cooked ham model with lactate 1h before HPP promoted a shift in the pathogen's central metabolism, favoring the metabolism of propanediol and ethanolamine together with the synthesis of the B12 cofactor. Moreover, the results suggest an activated methyl cycle that would promote modifications in membrane properties resulting in an enhanced resistance of the pathogen to HPP. This study provides insights on the mechanisms developed by in response to lactate and/or HPP and sheds light on the understanding of the piezo-protective effect of lactate.
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http://dx.doi.org/10.3390/biom11050677DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8147161PMC
April 2021

Exploring the Capability of Yeasts Isolated from Colombian Fermented Cocoa Beans to Form and Degrade Biogenic Amines in a Lab-Scale Model System for Cocoa Fermentation.

Microorganisms 2020 Dec 24;9(1). Epub 2020 Dec 24.

Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Via R. Balzarini 1, 64100 Teramo, Italy.

Yeast starters for cocoa fermentation are usually tested according to their enzymatic activities in terms of mucilage degradation and flavor improvement, disregarding their influence on the production or elimination of toxic compounds as biogenic amines (BAs), important for human health. In this work, we tested 145 strains belonging to 12 different yeast species and isolated from the Colombian fermented cocoa beans (CB) for their capability of producing BAs in vitro. Sixty-five strains were able to decarboxylate at least one of the amino acids tested. ECA33 (Pk) and 4 (Sc) were selected to evaluate their potential to modulate BAs, organic acids, and volatile organic compounds (VOCs) accumulation during a simulated cocoa fermentation. The growth of or in the presence of CB caused a significant reduction ( < 0.05) of 2-phenylethylamine (84% and 37%) and cadaverine (58% and 51%), and a significant increase of tryptamine and putrescine with a strong influence of temperature in BA formation and degradation. In addition, our findings pointed out that induced a major production of fatty acid- and amino acid-derived VOCs, while induced more VOCs derived from fatty acids metabolism. Our results suggest the importance of considering BA production in the choice of yeast starters for cocoa fermentation.
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http://dx.doi.org/10.3390/microorganisms9010028DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7823927PMC
December 2020

Influence of single nitrogen compounds on growth and fermentation performance of and during alcoholic fermentation.

Appl Environ Microbiol 2020 Dec 18. Epub 2020 Dec 18.

INRA, UMR1083, SPO, F-34060 Montpellier, France

Nitrogen is among the essential nutriments that govern interactions between yeast species in the wine environment. A thorough knowledge of how these yeasts assimilate the nitrogen compounds of grape juice is an important prerequisite for a successful co- or sequential fermentation. In the present study, we investigated the efficiency of 18 nitrogen sources for sustaining the growth and fermentation of two strains displaying metabolic properties, compared to the reference yeast The analysis of growth and fermentation parameters provided a comprehensive picture of preferences with respect to nitrogen sources for sustained growth and fermentation. Important differences were observed in regarding rates, final population and CO production. In particular, Lys and His supported substantial growth and fermentation contrary to while only 3 nitrogen sources, Arg, NH4 and Ser, promoted growth more efficiently than that of strains. Furthermore strains displayed a higher fermentative activity than during the first phase of culture with Gly or Thr, when the former species consumed solely fructose. Finally, no correlation has been shown between the ability of nitrogen sources to support growth and their fermentation efficiency. The specificities of regarding nitrogen sources preferences are related to its genetic background, but further investigations are needed to elucidate the molecular mechanisms involved. These data are essential elements to be taken into account in order to make the best use of the potential of the two species. Mixed fermentations combining non- and strains are increasingly implemented in the wine sector as they offer promising opportunities to diversify the flavour profile of end-products. However, competition for nutrients between species can cause fermentation problems, which is a severe hindrance to the development of these approaches. With the knowledge provided in this study on the nitrogen preferences of , winemakers will be able to set up a nitrogen nutrition scheme adapted to the requirement of each species during mixed fermentation, through must supplementation with relevant nitrogen compounds. This will prevent nitrogen depletion or competition between yeasts for nitrogen sources, and consequently potential issues during fermentation. The data of this study highlight the importance of an appropriate nitrogen resource management during co- or sequential fermentation for fully exploiting the phenotypic potential of non- yeasts.
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http://dx.doi.org/10.1128/AEM.02485-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8090893PMC
December 2020

Chloroanisoles occurrence in wine from grapes subjected to electrolyzed water treatments in the vineyard.

Food Res Int 2020 11 18;137:109704. Epub 2020 Sep 18.

USC 1422 GRAPPE, INRA, Ecole Supérieure d'Agricultures, SFR 4207 QUASAV, 55 rue Rabelais, 49100 Angers, France.

Recently the use of electrolyzed water (EW) attracted much attention as a high-performance, new technology for its potential use in the food industry. The aim of this work was to investigate the impact of grape EW treatments, applied at different time intervals prior to harvest, on the indigenous yeast populations of grape surface (Chenin blanc and Cabernet franc) and the occurrence of 2,4,6-trichloroanisole (TCA) in Cabernet franc wine. In addition, the evolution of inoculated and spontaneous fermentations on treated and non-treated grapes was also considered. The yeast population present on grape berries surface was influenced in a grape variety and EW treatment time-dependent way, since only Chenin blanc grapes treated with EW 7 days prior to harvest had significantly lower yeast population levels, compared to the respective control. Concerning the yeast diversity in the grape samples, a dominance of Aureobasidium pullulans was observed in treated grapes, independently of the grape variety. At the end of alcoholic fermentation, 2,4,6-trichloroanisole was detected in wine when the EW solution was applied at one or two weeks before harvest time. After wine storage, 2,4,6-trichloroanisole and chlorophenols contents generally exhibited a loss relative to initial values. The results showed that EW treatments tended to slightly increase the TCA concentration in final wine and did not affect the fermentation performances and chromatic properties of resulting wine. On the other hand, absorption or desorption phenomena by wine lees could be involved in the change of 2,4,6-trichloroanisole concentration in wine during storage time.
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http://dx.doi.org/10.1016/j.foodres.2020.109704DOI Listing
November 2020

Occurrence of Yeasts in White-Brined Cheeses: Methodologies for Identification, Spoilage Potential and Good Manufacturing Practices.

Front Microbiol 2020 15;11:582778. Epub 2020 Oct 15.

Department of Food Science, Faculty of Science, University of Copenhagen, Frederiksberg, Denmark.

Yeasts are generally recognized as contaminants in the production of white-brined cheeses, such as Feta and Feta-type cheeses. The most predominant yeasts species are , , , , , and spp. Although their spoilage potential varies at both species and strain levels, yeasts will, in case of excessive growth, present a microbiological hazard, effecting cheese quality. To evaluate the hazard and trace routes of contamination, the exact taxonomic classification of yeasts is required. Today, identification of dairy yeasts is mainly based on DNA sequencing, various genotyping techniques, and, to some extent, advanced phenotypic identification technologies. Even though these technologies are state of the art at the scientific level, they are only hardly implemented at the industrial level. Quality defects, caused by yeasts in white-brined cheese, are mainly linked to enzymatic activities and metabolism of fermentable carbohydrates, leading to production of metabolites (CO, fatty acids, volatile compounds, amino acids, sulfur compounds, etc.) and resulting in off-flavors, texture softening, discoloration, and swelling of cheese packages. The proliferation of spoilage yeast depends on maturation and storage conditions at each specific dairy, product characteristics, nutrients availability, and interactions with the co-existing microorganisms. To prevent and control yeast contamination, different strategies based on the principles of HACCP and Good Manufacturing Practice (GMP) have been introduced in white-brined cheese production. These strategies include milk pasteurization, refrigeration, hygienic sanitation, air filtration, as well as aseptic and modified atmosphere packaging. Though a lot of research has been dedicated to yeasts in dairy products, the role of yeast contaminants, specifically in white-brined cheeses, is still insufficiently understood. This review aims to summarize the current knowledge on the identification of contaminant yeasts in white-brined cheeses, their occurrence and spoilage potential related to different varieties of white-brined cheeses, their interactions with other microorganisms, as well as guidelines used by dairies to prevent cheese contamination.
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http://dx.doi.org/10.3389/fmicb.2020.582778DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7593773PMC
October 2020

Spatiotemporal Distribution of the Environmental Microbiota in Food Processing Plants as Impacted by Cleaning and Sanitizing Procedures: the Case of Slaughterhouses and Gaseous Ozone.

Appl Environ Microbiol 2020 11 10;86(23). Epub 2020 Nov 10.

Department of Agriculture, Forestry, and Food Sciences, University of Turin, Turin, Italy

Microbial complexity and contamination levels in food processing plants heavily impact the final product fate and are mainly controlled by proper environmental cleaning and sanitizing. Among the emerging disinfection technologies, ozonation is considered an effective strategy to improve the ordinary cleaning and sanitizing of slaughterhouses. However, its effects on contamination levels and environmental microbiota still need to be understood. For this purpose, we monitored the changes in microbiota composition in different slaughterhouse environments during the phases of cleaning/sanitizing and ozonation at 40, 20, or 4 ppm. Overall, the meat processing plant microbiota differed significantly between secondary processing rooms and deboning rooms, with a greater presence of psychrotrophic taxa in secondary processing rooms because of their lower temperatures. Cleaning/sanitizing procedures significantly reduced the contamination levels and in parallel increased the number of detectable operational taxonomic units (OTUs), by removing the masking effect of the most abundant human/animal-derived OTUs, which belonged to the phylum Subsequently, ozonation at 40 or 20 ppm effectively decreased the remaining viable bacterial populations. However, we could observe selective ozone-mediated inactivation of psychrotrophic bacteria only in the secondary processing rooms. There, the and abundances and their viable counts were significantly affected by 40 or 20 ppm of ozone, while more ubiquitous genera like showed a remarkable resistance to the same treatments. This study showed the effectiveness of highly concentrated gaseous ozone as an adjunct sanitizing method that can minimize cross-contamination and so extend the meat shelf life. Our survey demonstrates that RNA-based sequencing of 16S rRNA amplicons is a reliable approach to qualitatively probe, at high taxonomic resolution, the changes triggered by new and existing cleaning/sanitizing strategies in the environmental microbiota in human-built environments. This approach could soon represent a fast tool to clearly define which routine sanitizing interventions are more suitable for a specific food processing environment, thus limiting the costs of special cleaning interventions and potential product loss.
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http://dx.doi.org/10.1128/AEM.01861-20DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7657643PMC
November 2020

Functional Biodiversity of Yeasts Isolated from Colombian Fermented and Dry Cocoa Beans.

Microorganisms 2020 Jul 21;8(7). Epub 2020 Jul 21.

Faculty of Bioscience and Technology for Food, Agriculture and Environment, University of Teramo, Via R. Balzarini 1, 64100 Teramo, Italy.

Yeasts play an important role in the cocoa fermentation process. Although the most relevant function is the degradation of sugars and the production of ethanol, there is little understanding of the enzyme activities and attributes that allow them to survive even after drying. The present study explored the functional biodiversity of yeasts associated with Colombian cocoa fermented beans, able to survive after drying. Twelve species belonging to 10 genera of osmo-, acid-, thermo-, and desiccation-tolerant yeasts were isolated and identified from fermented and dry cocoa beans, with and standing out as the most frequent. For the first time, we reported the presence of in cocoa fermented beans. It was found that resistance to desiccation is related to the different degradation capacities of fermentation substrates, which suggests that associative relationships may exist between the different yeast species and their degradation products. Besides, the increased thermotolerance of some species was related to the presence of polyphenols in the medium, which might play a fundamental role in shaping the microbial community composition.
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http://dx.doi.org/10.3390/microorganisms8071086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7409280PMC
July 2020

Impact of Chemical and Alternative Fungicides Applied to Grapevine cv Nebbiolo on Microbial Ecology and Chemical-Physical Grape Characteristics at Harvest.

Front Plant Sci 2020 29;11:700. Epub 2020 May 29.

Department of Agricultural, Forest and Food Sciences, University of Turin, Grugliasco, Italy.

Viticulture is a cropping system in which treatment against fungal diseases (in particular powdery and downy mildews) can be extremely frequent. Accordingly, a reduction in antimicrobial treatments and the application of environmentally-friendly compounds are becoming increasingly important for a more sustainable viticulture. In addition to their effect against pathogens, the impact of these products on the quality of the grapes is very important for the oenological industries, but unfortunately at present few data are available. We evaluated the effect of the application of biocontrol products and resistance inducers in the vineyard on the mechanical properties, microbial ecology, technological and phenolic maturity of "Nebbiolo" grapes at harvest. The yield and vigor of vines were not influenced by the treatments, nor were the production of primary and secondary metabolites. However, the active ingredients influenced the mechanical properties of the skin (hardness and thickness). A significant hardening of the skin was detected when laminarin and chito-oligosaccharides were used, and sulfur induced a thickening of the skin with potential consequences for wine quality. Furthermore, the yeast community present on grape berries was influenced by the treatments. The abundance of , the dominant species on the grape berry, changed in response to the compounds used. In addition, sp. was reduced in some treatments with a potentially positive effect on the quality and the safety of the grapes. This study provides an overview of the effect of biocontrol products and resistance inducers on microbial ecology and "Nebbiolo" grape quality, contributing to the establishment of more sustainable and effective defense strategies in viticulture.
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http://dx.doi.org/10.3389/fpls.2020.00700DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7272676PMC
May 2020

Effect of mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae on management of malolactic fermentation.

Food Res Int 2020 08 17;134:109246. Epub 2020 Apr 17.

Department of Agricultural, Forest and Food Sciences, University of Torino, Largo Paolo Braccini 2, 10095 Grugliasco, Italy. Electronic address:

This work aims to improve the management of the malolactic fermentation (MLF) in red wines by elucidating the interactions between Starmerella bacillaris and Saccharomyces cerevisiae in mixed fermentations and malolactic bacteria. Two Starm. bacillaris strains were individually used in mixed fermentations with a commercial S. cerevisiae. MLF was performed using two autochthonous Lactobacillus plantarum and one commercial Oenococcus oeni inoculated following a simultaneous (together with S. cerevisiae) or sequential (at the end of alcoholic fermentation) approach. The impact of yeast inoculation on the progress of MLF was investigated by monitoring the viable microbial populations and the evolution of the main oenological parameters, as well as the volatile organic composition of the wines obtained in mixed and pure micro-scale winemaking trials. Our results indicated that MLF was stimulated, inhibited, or unaffected in mixed fermentations depending on the strains and on the regime of inoculation. O. oeni was able to perform MLF under all experimental conditions, and it showed a minimal impact on the volatile organic compounds of the wine. L. plantarum was unable to perform MLF in sequential inoculation assays, and strain-depending interactions with Starm. bacillaris were indicated as factor affecting the outcome of MLF. Moreover, uncompleted MLF were related to a lower aromatic complexity of the wines. Our evidences indicate that tailored studies are needed to define the appropriate management of non-Saccharomyces and malolactic starter cultures in order to optimize some technological parameters (i.e. reduction of vinification time) and to improve qualitative features (i.e. primary and secondary metabolites production) of red wines.
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http://dx.doi.org/10.1016/j.foodres.2020.109246DOI Listing
August 2020

Microbiota and volatilome profile of fresh and chill-stored deepwater rose shrimp (Parapenaeus longirostris).

Food Res Int 2020 06 1;132:109057. Epub 2020 Feb 1.

Lab. Marketing and Technology of Aquatic Products and Foods, Dept. of Ichthyology and Aquatic Environment, School of Agricultural Sciences, University of Thessaly, Fitokou street, 38446, N. Ionia, Volos, Greece.

Bacterial communities and Volatile Organic Compounds (VOCs) profile of deepwater rose shrimp (Parapenaeus longirostris) stored at 0 °C (ice) and 4 °C were investigated using 16S amplicon based sequencing and Solid phase micro-extraction (SPME) - Gas chromatography/mass spectrometry (GC/MS), respectively. The shelf-life of shrimps determined by sensory assessment was 5 and 2 days at 0 °C and 4 °C, respectively. Based on 16S analysis (culture-independed), the initial microbiota of shrimps mainly consists of Photobacterium, Candidatus Hepatoplasma, Psychrobacter, Acinetobacter and Delftia. Psychrobacter and Carnobacterium dominated during storage at both temperatures. Psychrobacter was the most dominant taxon at the end of shelf-life of chill-stored shrimps. A minor microbial population composed by Brevundimonas, Stenotrophomonas, Staphylococcus, Legionella, Acinetobacter, Bacillus, Escherichia-Shigella, Enterococcus, Enterobacter, Klebsiella was also detected. Those taxa may be originated from the environment due to an inadequate hygienic practice during fishing, handling and icing. VOCs such as ethanol, 3-methyl-1-butanol, 2-ethyl-1-hexanol, 3-hydroxy-2-butanone, indole etc., were found to be associated with shrimps at 4 °C, while acetone and dimethyl sulfide with shrimps in ice. Some VOCs, from microbial or chemical origin, increased in shrimps either at 0 °C (i.e. 1-octen-3-ol, trans-2-octenal) or at 4 °C (i.e. 3-methyl-1-butanol, indole), while 2-methylbutanal and 3-methylbutanal increased in both temperatures. A positive correlation between Psychrobacter with 2-ethyl-1-hexanol and Carnobacterium with 3-methyl-1-butanol was also observed. Concluding, we suggest the reinforcement of Good Hygiene Practices on fishing boats during fishing/handling, the rapid onboard icing and keeping shrimps iced avoiding even small increase of storage temperature that affects quality parameters (e.g. microbial population level, synthesis of microbiota, VOCs profile) in order to provide a product of the highest quality and safety in the market.
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http://dx.doi.org/10.1016/j.foodres.2020.109057DOI Listing
June 2020

Diet influences the functions of the human intestinal microbiome.

Sci Rep 2020 03 6;10(1):4247. Epub 2020 Mar 6.

Department of Agricultural, Forest and Food Science, University of Turin, Grugliasco, Italy.

Gut microbes programme their metabolism to suit intestinal conditions and convert dietary components into a panel of small molecules that ultimately affect host physiology. To unveil what is behind the effects of key dietary components on microbial functions and the way they modulate host-microbe interaction, we used for the first time a multi-omic approach that goes behind the mere gut phylogenetic composition and provides an overall picture of the functional repertoire in 27 fecal samples from omnivorous, vegan and vegetarian volunteers. Based on our data, vegan and vegetarian diets were associated to the highest abundance of microbial genes/proteins responsible for cell motility, carbohydrate- and protein-hydrolyzing enzymes, transport systems and the synthesis of essential amino acids and vitamins. A positive correlation was observed when intake of fiber and the relative fecal abundance of flagellin were compared. Microbial cells and flagellin extracted from fecal samples of 61 healthy donors modulated the viability of the human (HT29) colon carcinoma cells and the host response through the stimulation of the expression of Toll-like receptor 5, lectin RegIIIα and three interleukins (IL-8, IL-22 and IL-23). Our findings concretize a further and relevant milestone on how the diet may prevent/mitigate disease risk.
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http://dx.doi.org/10.1038/s41598-020-61192-yDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7060259PMC
March 2020

Antilisterial Effect and Influence on Gene Expression of Enterocin or in Sliced Dry-Cured Ham Stored at 7°C.

J Food Prot 2019 Sep;82(9):1598-1606

Department of Agricultural, Forest and Food Sciences, University of Torino, Grugliasco, Italy 10095 (ORCID: https://orcid.org/0000-0003-3774-6191 [V.A.]).

In this study, we focused on the effect of an enterocin or an strain added onto sliced dry-cured ham that was artificially inoculated with and stored at 7°C. The population of and the expression of five genes were monitored throughout the storage period. A persistent and a nonpersistent strain were tested, and both were influenced by the presence of the enterocin; both populations were reduced by more than 2 Log CFU/g after 14 days compared with the control, noninoculated ham. The presence of a bacteriocin-producing lactic acid bacterium, had a less pronounced effect on the viable counts for both strains. Concerning gene expression, a common trend observed for both strains in the presence of enterocin was the down-regulation of genes tested after 30 min of storage at 7°C. For the remainder of the storage period, the expression fluctuated but was mostly reduced. Similarly, the presence of led to an overall down-regulation of genes. The effect on gene expression of both enterocin and was more pronounced on the nonpersistent strain. Although the potential of a bacteriocin and a bacteriocin-producing microorganism to control was confirmed, this study highlights that gene expression may be influenced and needs to be evaluated when considering such biopreservation interventions.
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http://dx.doi.org/10.4315/0362-028X.JFP-19-024DOI Listing
September 2019

Effect of mixed species alcoholic fermentation on growth and malolactic activity of lactic acid bacteria.

Appl Microbiol Biotechnol 2019 Sep 6;103(18):7687-7702. Epub 2019 Aug 6.

Dipartimento di Scienze Agrarie, Forestali e Alimentari, Università degli Studi di Torino, Largo Braccini 2, 10095, Grugliasco, Italy.

In recent years, there is an increasing interest from the winemaking industry for the use of mixed fermentations with Starmerella bacillaris (synonym Candida zemplinina) and Saccharomyces cerevisiae, due to their ability to modulate metabolites of oenological interest. The current study was carried out to elucidate the effect of this fermentation protocol on the growth and malolactic activity of lactic acid bacteria (LAB) used for malolactic fermentation (MLF) and on the chemical and volatile profile of Nebbiolo wines and their chromatic characteristics. To this end, two LAB species, namely Lactobacillus plantarum and Oenococcus oeni, were inoculated at the beginning and at the end of the alcoholic fermentation (AF) performed by pure and mixed yeast using the abovementioned yeasts. The different yeast inoculation protocols and the combination of species tested influenced greatly the interactions and behavior of the inoculated yeasts and LAB during AF and MLF. For both LAB species, inoculation timing was critical to how rapidly MLF started and finished. Fermentation inoculated with L. plantarum, at the beginning of the AF, completed MLF faster than those inoculated with O. oeni. The presence of Starm. bacillaris in mixed fermentation promoted LAB growth and activity, in particular, O. oeni. Furthermore, LAB species choice had a greater impact on the volatile and chromatic profile of the wines than inoculation time. These findings reveal new knowledge about the importance of LAB species choice and inoculation time to ensure fast MLF completion and to improve wine characteristics in mixed fermentation with Starm. bacillaris and S. cerevisiae.
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http://dx.doi.org/10.1007/s00253-019-10064-1DOI Listing
September 2019

Saccharomyces cerevisiae-Starmerella bacillaris strains interaction modulates chemical and volatile profile in red wine mixed fermentations.

Food Res Int 2019 08 1;122:392-401. Epub 2019 Apr 1.

Università degli Studi di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Largo Braccini 2, 10095 Grugliasco, Italy. Electronic address:

The use of Starmerella bacillaris in combination with Saccharomyces cerevisiae is considered as a state-of-the-art biological application to modulate wine composition. This application implies a detailed understanding of yeast-yeast interactions during mixed fermentations and their effect on the composition of the resulting wines. In this context, ten commercial S. cerevisiae strains were used as partners of an indigenous, previously characterized Starm. bacillaris strain in order to get a better insight into the impact of S. cerevisiae strain employed. The different combinations of strains tested influenced the growth dynamics, the fermentation behavior and, as a consequence, wine composition in a couple-dependent manner. In addition, wines produced from mixed fermentations had significantly lower levels of ethanol, acetic acid and ethyl acetate, and showed higher amounts of glycerol, higher alcohols and esters compared to pure S. cerevisiae control fermentations. This study reveals the importance of S. cerevisiae strain choice on the chemical composition of the wines produced from mixed culture fermentations with Starm. bacillaris.
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http://dx.doi.org/10.1016/j.foodres.2019.03.072DOI Listing
August 2019

Probiotic potential of a Lactobacillus rhamnosus cheese isolate and its effect on the fecal microbiota of healthy volunteers.

Food Res Int 2019 05 5;119:305-314. Epub 2019 Feb 5.

Department of Agricultural, Forest and Food Sciences, University of Torino, Italy. Electronic address:

The present study describes an in vitro characterization of strains of lactic acid bacteria, focusing on physiological characters of probiotic interest, and a subsequent placebo-controlled, crossover administration trial, with a cohort of healthy volunteers. The strains of lactic acid bacteria were previously isolated from a fermented food (ripened cheese) and several ones resulted to have promising probiotic characteristics. Based on comprehensive evaluation of the data obtained, one strain was chosen and supplemented in a fermented milk. The fermented milk was then used in the administration trial with the goal of assessing its effect on the composition of the intestinal microbiota, as reflected in the feces. The fermented milk, with or without probiotic, had an effect on the intestinal microbiota and significant inter-individual differences were observed in response to the intervention. A common trend was observed related to two important populations of the human gut microbiota; a reduction in the relative abundance of Bacteroides and increase in the abundance of Prevotella in subjects during treatment compared to baseline were registered.
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http://dx.doi.org/10.1016/j.foodres.2019.02.004DOI Listing
May 2019

Effect of Atmospheric Pressure Plasma on Listeria monocytogenes Attached to Abiotic Surfaces.

J Food Prot 2019 Feb;82(2):233-237

1 Department of Agriculture, Forest and Food Sciences, University of Turin, Largo Braccini 2, Grugliasco, Turin, Italy (ORCID: http://orcid.org/0000-0003-3774-6191 [V.A.]).

Listeria monocytogenes can be introduced into food processing plants via raw material of animal or plant origin and can establish endemic populations through formation of biofilms. Biofilms are a continuous source of contamination for food products, and L. monocytogenes cells in biofilms are more resistant to stress and sanitizing agents than are planktonic cells. The use of gas-discharge plasmas may offer a feasible alternative to conventional sanitization methods. Plasmas are a mixture of charged particles, chemically reactive species, and UV radiation and can be used to destroy microorganisms. The purpose of this study was to measure the effectiveness of cold atmospheric pressure plasma (APP) treatments against bacteria attached to a solid surface and to evaluate the individual susceptibility of various L. monocytogenes strains. Attention was focused on the state of the cells after treatment, combining detection by viable counts and quantitative PCR (qPCR). Most of the culturable cells were inactivated after APP treatment, but the qPCR assay targeting the 16S rRNA revealed the presence of injured cells or their entrance into the viable but nonculturable state. These results were at least partly confirmed by a resuscitation experiment. After APP treatment, L. monocytogenes cell suspensions were incubated in brain heart infusion broth; some cells grew in the medium and therefore had survived the treatment. An understanding of the effects of APP on L. monocytogenes can inform the development of sanitation programs incorporating APP for pathogen removal. Methods other than those based of the culturability of the cells should be used to monitor pathogens in food processing plants because cultivation alone may underestimate the actual microbial load.
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http://dx.doi.org/10.4315/0362-028X.JFP-18-228DOI Listing
February 2019

Metataxonomic comparison between internal transcribed spacer and 26S ribosomal large subunit (LSU) rDNA gene.

Int J Food Microbiol 2019 Feb 10;290:132-140. Epub 2018 Oct 10.

Department of Agricultural, Forest, and Food Science, University of Turin, Largo Paolo Braccini 2, 10095 Grugliasco, Torino, Italy. Electronic address:

Next-generation sequencing has been used to strengthen knowledge about taxonomic diversity and ecology of fungi within food ecosystems. However, primer amplification and identification bias could edge our understanding into the fungal ecology. The aim of this study is to compare the performance of two primer pairs over two nuclear ribosomal RNA (rRNA) regions of the fungal kingdom, namely the ITS2 and 26S regions. Fermented cocoa beans were employed as biological material and the fungal ecology during fermentation was studied using amplicon-based sequencing tools, making use of a manually curated 26S database constructed in this study, and validated with SILVA's database. To explore potential biases introduced by PCR amplification of fungal communities, a mock community of known composition was prepared and tested. The relative abundances observed for ITS2 suggest that species with longer amplification fragments are underestimated and concurrently species that render shorter amplification fragments are overestimated. However, this correlation between amplicon length and estimation is not valid for all the species analysed. Variability in the amplification lengths contributed to the preferential amplification phenomenon. DNA extracted from twenty fermented cocoa bean samples were used to assess the performance of the two target regions. Overall, the metataxonomic data set recovered similar taxonomic composition and provided consistent results in OTU richness among biological samples. However, 26S region provided higher alpha diversity index and greater fungal rRNA taxonomic depth and robustness results compared with ITS2. Based on the results of this study we suggest the use of the 26S region for targeting fungi. Furthermore, this study showed the efficacy of the manually curated reference database optimized for annotation of mycobiota by using the 26S as a gene target.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2018.10.010DOI Listing
February 2019

Cell-to-cell contact mechanism modulates Starmerella bacillaris death in mixed culture fermentations with Saccharomyces cerevisiae.

Int J Food Microbiol 2019 Jan 12;289:106-114. Epub 2018 Sep 12.

Università degli Studi di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Largo Braccini 2, 10095 Grugliasco, Italy. Electronic address:

The use of mixed culture fermentations with selected Starmerella bacillaris and Saccharomyces cerevisiae strains is gaining winemaking attention, mainly due to their ability to enhance particular characteristics in the resulting wines. In this context, yeast interspecies interactions during fermentation have a fundamental role to determine the desired product characteristics, since they may modulate yeast growth and as a consequence metabolite production. In order to get an insight into these interactions, the growth and death kinetics of the abovementioned species were investigated in pure and mixed culture fermentations, using cv. Nebbiolo grape must. Trials were conducted in flasks but also in a double-compartment fermentation system in which cells of the two species were kept separate by a filter membrane. Although the two species had similar growth pattern during the first days of fermentation, Starm. bacillaris died earlier when tested in the flask than in the double-compartment fermentor. The early death of Starm. bacillaris seemed to be not caused by nutrient limitation nor by accumulation of growth inhibitory compounds (which were not measured in the present study). Rather, cell-to-cell contact mechanism, dependent on the presence of viable S. cerevisiae cells, appears to be responsible for the observations made. These results contribute to better understand the factors that influence Starm. bacillaris death during wine fermentations.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2018.09.009DOI Listing
January 2019

Microbiota dynamics and volatilome profile during stink bean fermentation (Sataw-Dong) with Lactobacillus plantarum KJ03 as a starter culture.

Food Microbiol 2018 Dec 26;76:91-102. Epub 2018 Apr 26.

Department of Agricultural, Forest and Food Science (DISAFA), University of Torino, Grugliasco, Torino 10095, Italy. Electronic address:

Sataw-Dong is a fermented stink bean in brine, made with Parkia speciosa subjected to spontaneous fermentation. This study aimed to investigate the impact of Lactobacillus plantarum KJ03 as a starter culture during Sataw-Dong fermentation and to determine its effect on the volatilome profile. Two fermentations were performed: spontaneous and inoculated with starter. The surface of the beans and the brines were separately analyzed throughout fermentation period for 15 days. Inoculated samples clearly showed a significantly higher acidification of the brine, reaching a pH of 3.98 within 5 days of fermentation. The microbiota was investigated through 16S amplicon based sequencing and revealed the dominance of Lactobacillus plantarum and Lactobacillus sanfranciscensis throughout the fermentation in both brine and bean samples. The starter used clearly influenced volatile organic compounds (VOCs) profiles. Inoculated samples showed the lowest abundance of Brevundimonas, Corynebacterium, Enterobacteriaceae, Methylobacterium and Klebsiella, compared to the spontaneous fermentation. Correlation between OTUs and VOCs revealed that acids, aldehydes, and alcohols exhibited a positive correlation with L. plantarum and L. sanfranciscencis. Overall aldehydes were mostly produced at the beginning, while acids, alcohols, and ketones at the middle until the end of the fermentation. Sataw-Dong produced with the starter significantly perceived a positive response in the overall acceptance. As shown through microbiological changes, acidification, VOCs and sensory analysis, the successful and accelerated Sataw-Dong fermentation was achieved when using a functional starter strain.
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http://dx.doi.org/10.1016/j.fm.2018.04.012DOI Listing
December 2018

A bioinformatics pipeline integrating predictive metagenomics profiling for the analysis of 16S rDNA/rRNA sequencing data originated from foods.

Food Microbiol 2018 Dec 24;76:279-286. Epub 2018 May 24.

University of Turin, Department of Agricultural, Forest and Food Sciences, Laboratory of Food Microbiology, Largo P. Braccini 2, 10095, Grugliasco, Turin, Italy.

The recent advances in molecular biology, such as the advent of next-generation sequencing (NGS) platforms, have paved the way to new exciting tools which rapidly transform food microbiology. Nowadays, NGS methods such as 16S rDNA/rRNA metagenomics or amplicon sequencing are used for the taxonomic profiling of the food microbial communities. Although 16S rDNA/rRNA NGS-based microbial data are not suited for the investigation of the functional potential of the identified operational taxonomic units as compared to shotgun metagenomics, advances in the bioinformatics discipline allow now the performance of such studies. In this paper, a bioinformatics workflow is described integrating predictive metagenomics profiling with specific application to food microbiology data. Bioinformatics tools pertinent to each sub-module of the pipeline are suggested as well. The published 16S rDNA/rRNA amplicon data originated from an Italian Grana-type cheese, using an NGS platform, was employed to demonstrate the predictive metagenomics profiling approach. The pipeline identified the microbial community and the changes that occurred in the microbial profile during manufacture of the food product studied (taxonomic profiling). The workflow also indicated significant changes in the functional profiling of the community. The tool may help to investigate the functional potential, alterations, and interactions of a microbial community. The proposed workflow may also find an application in the investigation of the ecology of foodborne pathogens encountered in various food products.
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http://dx.doi.org/10.1016/j.fm.2018.05.009DOI Listing
December 2018

Specific Phenotypic Traits of Starmerella bacillaris Related to Nitrogen Source Consumption and Central Carbon Metabolite Production during Wine Fermentation.

Appl Environ Microbiol 2018 08 1;84(16). Epub 2018 Aug 1.

SPO, INRA, SupAgro, Université de Montpellier, Montpellier, France

Over the last few years, the potential of non- yeasts to improve the sensory quality of wine has been well recognized. In particular, the use of in mixed fermentations with was reported as an appropriate way to enhance glycerol formation and reduce ethanol production. However, during sequential fermentation, many factors, such as the inoculation timing, strain combination, and physical and biochemical interactions, can affect yeast growth, the fermentation process, and/or metabolite synthesis. Among them, the availability of yeast-assimilable nitrogen (YAN), due to its role in the control of growth and fermentation, has been identified as a key parameter. Consequently, a comprehensive understanding of the metabolic specificities and the nitrogen requirements would be valuable to better exploit the potential of during wine fermentation. In this study, marked differences in the consumption of the total and individual nitrogen sources were registered between the two species, while the two strains generally behaved uniformly. strains are differentiated by their preferential uptake of ammonium compared with amino acids that are poorly assimilated or even produced (alanine). Otherwise, the non- yeast exhibits low activity through the acetaldehyde pathway, which triggers an important redistribution of fluxes through the central carbon metabolic network. In particular, the formation of metabolites deriving from the two glycolytic intermediates glyceraldehyde-3-phosphate and pyruvate is substantially increased during fermentations by This knowledge will be useful to better control the fermentation process in mixed fermentation with and Mixed fermentations using a controlled inoculation of and starter cultures represent a feasible way to modulate wine composition that takes advantage of both the phenotypic specificities of the non- strain and the ability of to complete wine fermentation. However, according to the composition of grape juices, the consumption by of nutrients, in particular of nitrogen sources, during the first stages of the process may result in depletions that further limit the growth of and lead to stuck or sluggish fermentations. Consequently, understanding the preferences of non- yeasts for the nitrogen sources available in grape must together with their phenotypic specificities is essential for an efficient implementation of sequential wine fermentations with and species. The results of our study demonstrate a clear preference for ammonium compared to amino acids for the non- species. This finding underlines the importance of nitrogen sources, which modulate the functional characteristics of inoculated yeast strains to better control the fermentation process and product quality.
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http://dx.doi.org/10.1128/AEM.00797-18DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6070767PMC
August 2018

Volatile profiles and chromatic characteristics of red wines produced with Starmerella bacillaris and Saccharomyces cerevisiae.

Food Res Int 2018 07 17;109:298-309. Epub 2018 Apr 17.

Università degli Studi di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Largo Braccini 2, 10095 Grugliasco, Italy. Electronic address:

The use of mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae is gaining attention in recent years due to their ability to modulate the metabolites production of enological interest. In the present study, four of the most popular planted red grape varieties (Cabernet sauvignon, Merlot, Pinot noir and Shiraz) were fermented using the aforementioned species and two different inoculation protocols (inoculation of S. cerevisiae after 24 and 48 h from the Starm. bacillaris inoculation), in order to evaluate their impact on the volatile composition and chromatic characteristics of wines. Analysis from chemical composition showed that titratable acidity and glycerol content exhibited marked differences among wines after fermentation. For volatile compounds, mixed fermented wines using an inoculation delay of 48 h led to reduction of volatile compounds (mainly esters). A shorter 24 h delay produced wines with higher values of color intensity than pure fermented wines. The differences observed between the inoculation protocols can be explained by the growth dynamics of both species during fermentation. These findings suggest that mixed fermentations posed a great potential in reducing metabolites which are considered negative for wine quality (mainly ethyl acetate and volatile fatty acids) and with an improvement of the chromatic profile of the wines.
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http://dx.doi.org/10.1016/j.foodres.2018.04.027DOI Listing
July 2018

Sausage fermentation and starter cultures in the era of molecular biology methods.

Int J Food Microbiol 2018 Aug 25;279:26-32. Epub 2018 Apr 25.

University of Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Largo Braccini 2, 10095 Grugliasco, Torino, Italy. Electronic address:

Fermented sausages have a long tradition originating from Europe and they constitute a significant part of the Mediterranean diet. This kind of products has a specific microbiota that is typical of the region or area where they are produced. Therefore, in order to protect the traditional aspect of these products, it is essential to understand the microbial ecology during fermentation by studying the dynamic changes that occur and to select autochthonous starter cultures that can be used in the production. In this paper we summarize the state of the art concerning the selection and use of starter cultures and ecology aspects of naturally fermented sausages. We pay particular attention to the application of bacteriocinogenic strains as they could provide an additional tool in the prevention of foodborne pathogens as well as enhancing the competitiveness of the starter organisms. Microbial ecology of fermented sausages has been determined by traditional microbiological methods, but the introduction in food microbiology of new molecular techniques complements the studies carried out so far and allows scientists to overcome the limitations of traditional methods. Next Generation Sequencing (NGS) techniques represent a change in the way microbiologists address ecology and diversity in foods. Indeed the application of metataxonomics and metagenomics will permit a detailed understanding of microbial ecology. A thorough knowledge of the mechanisms behind the biological processes will enhance meat fermentation control and modulation to obtain products with desired organoleptic properties.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2018.04.038DOI Listing
August 2018

Volatile profile of white wines fermented with sequential inoculation of Starmerella bacillaris and Saccharomyces cerevisiae.

Food Chem 2018 Aug 7;257:350-360. Epub 2018 Mar 7.

Università degli Studi di Torino, Dipartimento di Scienze Agrarie, Forestali e Alimentari, Largo Braccini 2, 10095 Grugliasco, Italy. Electronic address:

Mixed fermentations with Starmerella bacillaris and Saccharomyces cerevisiae affect the chemical composition of wines, by modulating various metabolites of oenological interest. The current study was carried out to elucidate the effect of sequential inoculation of the above mentioned species on the production of white wines, especially on the chemical and aromatic characteristics of Chardonnay, Muscat, Riesling and Sauvignon blanc wines. Titratable acidity and glycerol content exhibited evident differences among the wines after fermentation. For volatile compounds, mixed fermentations led to a reduction of the total esters, including ethyl acetate, which is a compound responsible for wine deterioration. However, Sauvignon blanc wines fermented by mixed cultures contained significantly higher levels of esters and thiols, both associated with positive sensory attributes. These findings suggest that sequential inoculations possess great potential in affecting and modulating the chemical and aromatic profile of white wines, especially those produced from Sauvignon blanc grapes.
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http://dx.doi.org/10.1016/j.foodchem.2018.03.018DOI Listing
August 2018

Fructose liquid and solid formulations differently affect gut integrity, microbiota composition and related liver toxicity: a comparative in vivo study.

J Nutr Biochem 2018 05 13;55:185-199. Epub 2018 Feb 13.

Dept. of Drug Science and Technology, University of Turin, Italy. Electronic address:

Despite clinical findings suggesting that the form (liquid versus solid) of the sugars may significantly affect the development of metabolic diseases, no experimental data are available on the impact of their formulations on gut microbiota, integrity and hepatic outcomes. In the present sudy, C57Bl/6j mice were fed a standard diet plus water (SD), a standard diet plus 60% fructose syrup (L-Fr) or a 60% fructose solid diet plus water (S-Fr) for 12 weeks. Gut microbiota was characterized through 16S rRNA phylogenetic profiling and shotgun sequencing of microbial genes in ileum content and related volatilome profiling. Fructose feeding led to alterations of the gut microbiota depending on the fructose formulation, with increased colonization by Clostridium, Oscillospira and Clostridiales phyla in the S-Fr group and Bacteroides, Lactobacillus, Lachnospiraceae and Dorea in the L-Fr. S-Fr evoked the highest accumulation of advanced glycation end products and barrier injury in the ileum intestinal mucosa. These effects were associated to a stronger activation of the lipopolysaccharide-dependent proinflammatory TLR4/NLRP3 inflammasome pathway in the liver of S-Fr mice than of L-Fr mice. In contrast, L-Fr intake induced higher levels of hepatosteatosis and markers of fibrosis than S-Fr. Fructose-induced ex novo lipogenesis with production of SCFA and MCFA was confirmed by metagenomic analysis. These results suggest that consumption of fructose under different forms, liquid or solid, may differently affect gut microbiota, thus leading to impairment in intestinal mucosa integrity and liver homeostasis.
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http://dx.doi.org/10.1016/j.jnutbio.2018.02.003DOI Listing
May 2018

Next generation microbiological risk assessment: opportunities of whole genome sequencing (WGS) for foodborne pathogen surveillance, source tracking and risk assessment.

Int J Food Microbiol 2018 Dec 1;287:3-9. Epub 2017 Dec 1.

Safety and Environmental Assurance Centre, Unilever, Colworth Science Park, Sharnbrook, Bedfordshire MK44 1LQ, UK.

Whole genome sequencing (WGS) of important foodborne pathogens is a technology under development, but is already employed in routine surveillance by public health agencies and is being increasingly exploited in tracing transmission routes and identifying contamination events (source tracking) that take place in the farm-to-fork continuum. Furthermore, data generated from WGS, complemented by other -omics data, have the potential to be integrated into and strengthen microbiological risk assessment. In this paper, we discuss the contribution of WGS in diverse areas important to food safety and public health. Additionally, an outlook of future WGS applications, which should contribute to our understanding of the ecology and physiology of foodborne microorganisms, is presented.
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http://dx.doi.org/10.1016/j.ijfoodmicro.2017.11.007DOI Listing
December 2018

Shotgun Metagenomics and Volatilome Profile of the Microbiota of Fermented Sausages.

Appl Environ Microbiol 2018 02 17;84(3). Epub 2018 Jan 17.

DISAFA, Microbiology and Food Technology Sector, University of Turin, Grugliasco, Italy

Changes in the microbial gene content and abundance can be analyzed to detect shifts in the microbiota composition due to the use of a starter culture in the food fermentation process, with the consequent shift of key metabolic pathways directly connected with product acceptance. Meat fermentation is a complex process involving microbes that metabolize the main components in meat. The breakdown of carbohydrates, proteins, and lipids can lead to the formation of volatile organic compounds (VOCs) that can drastically affect the organoleptic characteristics of the final products. The present meta-analysis, performed with the shotgun DNA metagenomic approach, focuses on studying the microbiota and its gene content in an Italian fermented sausage produced by using a commercial starter culture (a mix of and ), with the aim to discover the connections between the microbiota, microbiome, and the release of volatile metabolites during ripening. The inoculated fermentation with the starter culture limited the development of and reduced the microbial diversity compared to that from spontaneous fermentation. KEGG database genes associated with the reduction of acetaldehyde to ethanol (EC 1.1.1.1), acetyl phosphate to acetate (EC 2.7.2.1), and 2,3-butanediol to acetoin (EC 1.1.1.4) were most abundant in inoculated samples (I) compared to those in spontaneous fermentation samples (S). The volatilome profiles were highly consistent with the abundance of the genes; elevated acetic acid (1,173.85 μg/kg), ethyl acetate (251.58 μg/kg), and acetoin (1,100.19 μg/kg) were observed in the presence of the starters at the end of fermentation. Significant differences were found in the liking of samples based on flavor and odor, suggesting a higher preference by consumers for the spontaneous fermentation samples. Inoculated samples exhibited the lowest scores for the liking data, which were clearly associated with the highest concentration of acetic acid. We present an advance in the understanding of meat fermentation by coupling DNA sequencing metagenomics and metabolomics approaches to describe the microbial function during this process. Very few studies using this global approach have been dedicated to food, and none have examined sausage fermentation, underlying the originality of the study. The starter culture drastically affected the organoleptic properties of the products. This finding underlines the importance of starter culture selection that takes into consideration the functional characteristics of the microorganism to optimize production efficiency and product quality.
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http://dx.doi.org/10.1128/AEM.02120-17DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5772244PMC
February 2018

Genomic assessment in Lactobacillus plantarum links the butyrogenic pathway with glutamine metabolism.

Sci Rep 2017 11 21;7(1):15975. Epub 2017 Nov 21.

Department of Forestry, Agriculture and Food Sciences, University of Torino, Turin, Italy.

The butyrogenic capability of Lactobacillus (L.) plantarum is highly dependent on the substrate type and so far not assigned to any specific metabolic pathway. Accordingly, we compared three genomes of L. plantarum that showed a strain-specific capability to produce butyric acid in human cells growth media. Based on the genomic analysis, butyric acid production was attributed to the complementary activities of a medium-chain thioesterase and the fatty acid synthase of type two (FASII). However, the genomic islands of discrepancy observed between butyrogenic L. plantarum strains (S2T10D, S11T3E) and the non-butyrogenic strain O2T60C do not encompass genes of FASII, but several cassettes of genes related to sugar metabolism, bacteriocins, prophages and surface proteins. Interestingly, single amino acid substitutions predicted from SNPs analysis have highlighted deleterious mutations in key genes of glutamine metabolism in L. plantarum O2T60C, which corroborated well with the metabolic deficiency suffered by O2T60C in high-glutamine growth media and its consequent incapability to produce butyrate. In parallel, the increase of glutamine content induced the production of butyric acid by L. plantarum S2T10D. The present study reveals a previously undescribed metabolic route for butyric acid production in L. plantarum, and a potential involvement of the glutamine uptake in its regulation.
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http://dx.doi.org/10.1038/s41598-017-16186-8DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5698307PMC
November 2017