Abstract
Kombucha, historically an Asian tea-based fermented drink, has recently become trendy in Western countries. Producers claim it bears health-enhancing properties that may come from the tea or ...metabolites produced by its microbiome. Despite its long history of production, microbial richness and dynamics have not been fully unraveled, especially at an industrial scale. Moreover, the impact of tea type (green or black) on microbial ecology was not studied. Here, we compared microbial communities from industrial-scale black and green tea fermentations, still traditionally carried out by a microbial biofilm, using culture-dependent and metabarcoding approaches. Dominant bacterial species belonged to Acetobacteraceae and to a lesser extent Lactobacteriaceae, while the main identified yeasts corresponded to Dekkera, Hanseniaspora and Zygosaccharomyces during all fermentations. Species richness decreased over the 8-day fermentation. Among acetic acid bacteria, Gluconacetobacter europaeus, Gluconobacter oxydans, G. saccharivorans and Acetobacter peroxydans emerged as dominant species. The main lactic acid bacteria, Oenococcus oeni, was strongly associated with green tea fermentations. Tea type did not influence yeast community, with Dekkera bruxellensis, D. anomala, Zygosaccharomyces bailii and Hanseniaspora valbyensis as most dominant. This study unraveled a distinctive core microbial community which is essential for fermentation control and could lead to Kombucha quality standardization.
Microbial ecology of industrial Kombucha fermentations.
Some foods and feeds are often contaminated by numerous mycotoxins, but most studies have focused on the occurrence and toxicology of a single mycotoxin. Regulations throughout the world do not ...consider the combined effects of mycotoxins. However, several surveys have reported the natural co-occurrence of mycotoxins from all over the world. Most of the published data has concerned the major mycotoxins aflatoxins (AFs), ochratoxin A (OTA), zearalenone (ZEA), fumonisins (FUM) and trichothecenes (TCTs), especially deoxynivalenol (DON). Concerning cereals and derived cereal product samples, among the 127 mycotoxin combinations described in the literature, AFs+FUM, DON+ZEA, AFs+OTA, and FUM+ZEA are the most observed. However, only a few studies specified the number of co-occurring mycotoxins with the percentage of the co-contaminated samples, as well as the main combinations found. Studies of mycotoxin combination toxicity showed antagonist, additive or synergic effects depending on the tested species, cell model or mixture, and were not necessarily time- or dose-dependent. This review summarizes the findings on mycotoxins and their co-occurrence in various foods and feeds from all over the world as well as in vitro experimental data on their combined toxicity.
Food spoilage is a major issue for the food industry, leading to food waste, substantial economic losses for manufacturers and consumers, and a negative impact on brand names. Among causes, fungal ...contamination can be encountered at various stages of the food chain (e.g., post-harvest, during processing or storage). Fungal development leads to food sensory defects varying from visual deterioration to noticeable odor, flavor, or texture changes but can also have negative health impacts via mycotoxin production by some molds. In order to avoid microbial spoilage and thus extend product shelf life, different treatments-including fungicides and chemical preservatives-are used. In parallel, public authorities encourage the food industry to limit the use of these chemical compounds and develop natural methods for food preservation. This is accompanied by a strong societal demand for 'clean label' food products, as consumers are looking for more natural, less severely processed and safer products. In this context, microbial agents corresponding to bioprotective cultures, fermentates, culture-free supernatant or purified molecules, exhibiting antifungal activities represent a growing interest as an alternative to chemical preservation. This review presents the main fungal spoilers encountered in food products, the antifungal microorganisms tested for food bioprotection, and their mechanisms of action. A focus is made in particular on the recent in situ studies and the constraints associated with the use of antifungal microbial agents for food biopreservation.
Domestication provides an excellent framework for studying adaptive divergence. Using population genomics and phenotypic assays, we reconstructed the domestication history of the blue cheese mould ...Penicillium roqueforti. We showed that this fungus was domesticated twice independently. The population used in Roquefort originated from an old domestication event associated with weak bottlenecks and exhibited traits beneficial for pre‐industrial cheese production (slower growth in cheese and greater spore production on bread, the traditional multiplication medium). The other cheese population originated more recently from the selection of a single clonal lineage, was associated with all types of blue cheese worldwide except Roquefort, and displayed phenotypes more suited for industrial cheese production (high lipolytic activity, efficient cheese cavity colonization ability and salt tolerance). We detected genomic regions affected by recent positive selection and putative horizontal gene transfers. This study sheds light on the processes of rapid adaptation and raises questions about genetic resource conservation.
see also the Perspective by Brigida Gallone, Jan Steensels and Kevin J. Verstrepen.
Deoxynivalenol (DON) and zearalenone (ZEA) are mycotoxins primarily produced by Fusarium species and commonly co-occur in European grains. Some in vitro studies reported synergistic combined effects ...on cell viability reduction for these two natural food contaminants. However, most of these studies were carried out on conventional cell culture systems involving only one cell type and thus did not include cell-cell communication that is closer to in vivo conditions. In this context, we developed easy bi- and tri-culture systems using the Caco-2 (intestinal epithelial cells), THP-1 (monocytes) and HepaRG (hepatic cells) human cell lines in a proliferating state. Individual and combined cytotoxic effects of DON and ZEA were then assessed using co-cultures during 48 h. In bi-culture systems, results showed that only the highest tested dose of ZEA (IC30) induced a significant reduction in THP-1 viability with both Caco-2 and HepaRG cells cultured in transwells above. On the contrary, only the highest tested dose of DON (IC30) significantly affected HepaRG cell viability located under the Caco-2 cell monolayer. In addition, the DON + ZEA combination seemed to induce higher cytotoxicity than each toxin alone. Mycotoxin quantification in the abluminal compartment by Q-TOF LC-MS suggested uptake of both mycotoxins by the different cell lines. According to the co-culturing cell type, possible cell-cell interactions were also observed. Finally, in the tri-culture system, no cytotoxic effects were observed, regardless of the treatment. These findings highlighted the importance of the proposed models to better decipher toxicological impacts of mycotoxins on more complex cellular systems.
•The DON + ZEA mixture led to synergism on cell mortality at the highest tested dose.•When the culture system complexity increased, the mycotoxin cytotoxic effect decreased.•Cell-cell interactions modulated the cell response to the mycotoxin exposure.
Food fraud, corresponding to any intentional action to deceive purchasers and gain an undue economical advantage, is estimated to result in a 10 to 65 billion US dollars/year economical cost ...worldwide. Dairy products, such as cheese, in particular cheeses with protected land- and tradition-related labels, have been listed as among the most impacted as consumers are ready to pay a premium price for traditional and typical products. In this context, efficient food authentication methods are needed to counteract current and emerging frauds. This review reports the available authentication methods, either chemical, physical, or DNA-based methods, currently used for origin authentication, highlighting their principle, reported application to cheese geographical origin authentication, performance, and respective advantages and limits. Isotope and elemental fingerprinting showed consistent accuracy in origin authentication. Other chemical and physical methods, such as near-infrared spectroscopy and nuclear magnetic resonance, require more studies and larger sampling to assess their discriminative power. Emerging DNA-based methods, such as metabarcoding, showed good potential for origin authentication. However, metagenomics, providing a more in-depth view of the cheese microbiota (up to the strain level), but also the combination of methods relying on different targets, can be of interest for this field.
Penicillium roqueforti is a common food and feed contaminant. However, it is also worldwide renowned for its use as a technological culture responsible for the typicity of blue-veined cheese. Members ...of the P. roqueforti species are also known to be able to produce secondary metabolites including mycophenolic acid (MPA) and roquefortine C (ROQ C) mycotoxins. In order to more closely simulate the reality of mycotoxin exposure through contaminated food consumption, this work investigated the toxicological effects of MPA and ROQ C not only in acute but also in chronic (i.e. 21-days continuous exposure) conditions on Caco-2 cells. Acute exposure to high MPA or ROQ C concentrations induced an increase of IL-8 secretion. Effects of 21-days continuous exposure on barrier integrity, based on concentrations found in blue-veined cheese and mean of blue cheese intake by French consumers, were monitored. Concerning exposure to ROQ C, no alteration of the intestinal barrier was observed. In contrast, the highest tested MPA concentration (780 μM) induced a decrease in the barrier function of Caco-2 cell monolayers, but no paracellular passage of bacteria was observed. This study highlighted that exposure to MPA and ROQ C average concentrations found in blue-veined cheese does not seem to induce significant toxicological effects in the tested conditions.
•Acute exposure to high MPA or ROQ C induced an increase of IL-8 secretion.•Continuous exposure for 21 days to ROQ C did not lead to alteration of the intestinal barrier.•Continuous exposure for 21 days to high MPA concentration induced decrease in barrier function.
Mycotoxins, produced by fungi, frequently occur at different stages in the food supply chain between pre- and postharvest. Globally produced cereal crops are known to be highly susceptible to ...contamination, thus constituting a major public health concern. Among the encountered mycotoxigenic fungi in cereals,
spp. are the most frequent and produce both regulated (i.e., T-2 toxin, deoxynivalenol -DON-, zearalenone -ZEA-) and emerging (i.e., enniatins -ENNs-, beauvericin -BEA-) mycotoxins. In this study, we investigated the in vitro cytotoxic effects of regulated and emerging fusariotoxins on HepaRG cells in 2D and 3D models using undifferentiated and differentiated cells. We also studied the impact of ENN B1 and ENN B exposure on gene expression of HepaRG spheroids. Gene expression profiling pinpointed the differentially expressed genes (DEGs) and overall similar pathways were involved in responses to mycotoxin exposure. Complement cascades, metabolism, steroid hormones, bile secretion, and cholesterol pathways were all negatively impacted by both ENNs. For cholesterol biosynthesis, 23/27 genes were significantly down-regulated and could be correlated to a 30% reduction in cholesterol levels. Our results show the impact of ENNs on the cholesterol biosynthesis pathway for the first time. This finding suggests a potential negative effect on human health due to the essential role this pathway plays.
Formation of biogenic amines (BA) may occur in fermented foods and beverages due to the amino acid decarboxylase activities of Gram-positive bacteria. These compounds may cause food poisoning and ...therefore could imply food exportation problems. A set of consensual primers based on histidine decarboxylase gene (
hdc) sequences of different bacteria was designed for the detection of histamine-producing Gram-positive bacteria. A multiplex PCR based on these
hdc primers and recently designed primers targeting the tyrosine decarboxylase (
tyrdc) gene was created. A third set of primers targeting the 16S rRNA gene of eubacteria was also used as an internal control. This multiplex PCR was performed on extracted DNA as well as directly on cell colonies. The results obtained show that this new molecular tool allowed for the detection of Gram-positive histamine- and/or tyramine-producing bacteria. The use of this molecular tool for early and rapid detection of Gram-positive BA-producing bacteria is of interest in evaluating the potential of cultured indigenous strains to produce biogenic amines in a fermented food product as well as to validate the innocuity of potential starter strains in the food industry.
Consumer's demand for naturally preserved food products is growing and the use of bioprotective cultures is an alternative to chemical preservatives or a complementary tool to hurdle technologies to ...avoid or delay fungal spoilage of dairy products. To develop antifungal cultures for the dairy product biopreservation, experiments were conducted both
and
. Firstly, the antifungal activity of 32 strains of lactic acid bacteria (LAB) and propionibacteria was screened alone, and then on combinations based on 5 selected lactobacilli strains. This screening was performed in yogurt and cheese models against four major spoilage fungi previously isolated from contaminated dairy products (
, and
). Selected combinations were then tested as adjunct cultures in sour cream and semi-hard cheeses produced at a pilot scale to evaluate their antifungal activity during challenge tests against selected fungal targets (
, and
) and shelf life tests; and their impact on product organoleptic properties. The screening step allowed selecting two binary combinations, A1 and A3 composed of
L244 and either
L172 or
CIRM-BIA1113, respectively.
assays showed that the A1 combination delayed the growth of
and
for 2-24 days on sour cream depending of the antifungal culture inoculum, without effect on organoleptic properties at low inoculum (10
colony-forming units (CFU)/mL). Moreover, the A1 and A3 combinations also delayed the growth of
in semi-hard cheese for 1-6 days and 1 day, respectively. Antifungal cultures neither impacted the growth of starter cultures in both sour cream and cheese nor the products' pH, although post acidification was observed in sour cream supplemented with these combinations at the highest concentrations (2.10
CFU/mL). The combination of both
and
screening assays allowed developing 2 antifungal combinations exhibiting significant antifungal activity and providing future prospects for use as bioprotective cultures in dairy products.
PDF
