[Show abstract][Hide abstract] ABSTRACT: To gain some specific insight into the roles microorganisms might play in non-alcoholic fatty liver disease (NAFLD), some intestinal and lactic acid bacteria and one yeast (Anaerostipes caccae, Bacteroides thetaiotaomicron, Bifidobacterium longum, Enterococcus fecalis, Escherichia coli, Lactobacillus acidophilus, Lactobacillus fermentum, Lactobacillus plantarum, Weissella confusa, Saccharomyces cerevisiae) were characterized by high performance liquid chromatography for production of ethanol when grown on different carbohydrates: hexoses (glucose and fructose), pentoses (arabinose and ribose), disaccharides (lactose and lactulose), and inulin. Highest amounts of ethanol were produced by S. cerevisiae, L. fermentum and W. confusa on glucose and by S. cerevisiae and W. confusa on fructose. Due to mannitol-dehydrogenase expressed in L. fermentum, ethanol production on fructose was significantly (P < 0.05) reduced. Pyruvate and citrate, two potential electron acceptors for regeneration of NAD+/NADP+, drastically reduced ethanol production with acetate produced instead in L. fermentum grown on glucose and W. confusa grown on glucose and fructose, respectively. In fecal slurries prepared from feces of four overweight volunteers, ethanol was found to be produced upon addition of fructose. Addition of A. caccae, L. acidophilus, L. fermentum, as well as citrate and pyruvate, respectively, abolished ethanol production. However, addition of W. confusa resulted in significantly (P < 0.05) increased production of ethanol. These results indicate that microorganisms like W. confusa, a hetero-fermentative, mannitol-dehydrogenase negative lactic acid bacterium, may promote NAFLD through ethanol produced from sugar fermentation, while other intestinal bacteria and homo- and hetero-fermentative but mannitol-dehydrogenase positive lactic acid bacteria may not promote NAFLD. Also, our studies indicate that dietary factors interfering with gastrointestinal microbiota and microbial metabolism may be important in preventing or promoting NAFLD.
Full-text · Article · Jan 2016 · Frontiers in Microbiology
[Show abstract][Hide abstract] ABSTRACT: Bacteria belonging to the genus Lactobacillus are used as starter cultures or that develop naturally as fermenting microbiota in the production of various foods. On the detrimental side, lactobacilli may act as reservoir of antibiotic resistance genes, which can spread to commensal bacteria in humans or animals, or to food-associated pathogens. In the last decade, advances in molecular biology and in genome sequencing have provided more information on antibiotic resistances in foodborne bacteria. The aim of this review was to consider and provide an up-to-date status on phenotypic and genotypic antibiotic resistance profiles in Lactobacillus species from fermented foods and also to highlight new information on the distribution of glycopeptide and chloramphenicol resistance genes in Lactobacillus genomes. In silico screening of vanZ (vancomycin resistance) and cat (chloramphenicol resistance)-like sequences in Lactobacillus species isolated from fermented foods revealed for the first time the occurrence of vanZ and cat genes in Lactobacillus species being highly conserved genes in the chromosome of each species, presumably non-transferable. Further studies involving genome sequences of Lactobacillus isolated from fermented foods, especially those relying on spontaneous fermentation, is crucial to increase knowledge on the potential presence and spread of antibiotic resistance genes via the food route.
Full-text · Article · Sep 2015 · Food Research International
[Show abstract][Hide abstract] ABSTRACT: Background and Objectives: Some years ago, egg consumption was considered to be bad for heart health, blood vessels or for people watching their cholesterol levels. Meanwhile, recent meta-analysis studies concluded that higher consumption of egg is not associated with increased risk of cardiovascular disease. This discrepancy raises an important question as to whether the gut microbiota plays a role in digestion, absorption and metabolism of eggs in the digestive tract. There are four primary ways in which eggs (or egg consumption) can impact on the composition of the intestinal microbiota: a) by its nutrition-related factors; through its microbiological status; b) through the potential presence of residues of drugs applied to laying hens; and d) through its allergens. Current studies suggest that high dietary fat intake may contribute to metabolic syndrome pathogenesis through altering intestinal microbiota (a decrease in gut barrier-protecting beneficial Bifidobacteria spp. population and an increase in E coli population), increasing intestinal permeability, and promoting inflammation [Brown et al., 2012; Martinez-Medina et al., 2014]. Because per capita consumption of egg has increased continuously (221 – 259 eggs) and eggs contain high levels of cholesterol and saturated-fat, we were interested in investigating whether egg consumption and egg microbiota impact on the composition of the gut microbiota and immunological/metabolic/inflammatory biomarkers in vitro, ex vivo and in vivo. Materials and Methods: Briefly, freshly defecated fecal pellets were collected aseptically from 6 – 8 donor mice, weighed, and then placed in 200 ml of MRS broth. The fecal pellets were resuspended in 200 ml MRS broth by vortexing and by gently bashing with a sterile bacteriological loop, and the resulting cell suspensions were incubated anaerobically without or with whole boiled eggs at 37 °C for 24h. After incubation, serial dilutions were made in sterile PBS and suitable dilutions were plated onto MRS agar for anaerobic culturable bacteria. Afterwards, MRS agar plates were incubated anaerobically at 37 °C for 48 hours and the numbers of colonies on the plates were counted. After the plating process, bacterial cultures were used to measure pH values. For the first time, we used Konelab 20i Clinical Chemistry Analyzer to assess the actual rate of glucose consumption by bacteria, as manifested by quantitative measurement of glucose concentrations in bacterial cell-free culture supernatants (showing the rate of glucose disappearance). However, we conducted similar experimental series with a pure culture of the human-derived Bifidobacterium DSM 20086 strain. Results: Our preliminary in vitro and ex vivo experiments show that addition of egg to MRS broth medium did not inhibit, but rather augmented the growth of culturable anaerobic bacteria from mouse faeces as well as human intestinal-derived Bifidobacterium DSM 20086 strain, as manifested by higher bacterial counts (CFU/ml). This was associated with lower pH values and glucose concentrations in bacterial cultures as reliable and quantitative indicators for prediction of the rate of glucose utilization. Conclusion: Overall, our experiments show that although egg contains high cholesterol and saturated-fat contents, it has not any demonstrably negative impacts on bacterial growth parameters in culturable anaerobic bacteria from mouse faeces as well as human-derived Bifidobacterium DSM 20086 strain. If this happens in vivo, then egg consumption may beneficially modify gut microbiota community composition, which in turn may play a favorable role in the digestion, absorption and metabolism of egg in the digestive tract. Our ongoing cell culture and in vivo studies will provide additional insights into the molecular and cellular basis, underpinning the interplay between egg metabolism and gut microbiota composition.
[Show abstract][Hide abstract] ABSTRACT: A systematic investigation was carried out on the influence of fermentation on glucosinolates and their
degradation products from fresh raw cabbage, throughout fermentation at 20 �C and storage at 4 �C.
Glucosinolates were degraded dramatically between Day 2 and 5 of fermentation and by Day 7 there
was no detectable amount of glucosinolates left. Fermentation led to formation of potential bioactive
compounds ascorbigen (13.0 lmol/100 g FW) and indole-3-carbinol (4.52 lmol/100 g FW) with their
higher concentrations from Day 5 to Day 9. However, during storage indole-3-carbinol slowly degraded
to 0.68 lmol/100 g FW, while ascorbigen was relatively stable from Week 4 until Week 8 at
6.78 lmol/100 g FW. In contrast, the content of indole-3-acetonitrile decreased rapidly during fermentation
from 3.6 to 0.14 lmol/100 g FW. The results imply a maximum of health beneficial compounds after
fermentation (7–9 days) in contrast to raw cabbage or stored sauerkraut.
[Show abstract][Hide abstract] ABSTRACT: Bacteria assigned to the genus Weissella are Gram-positive, catalase-negative, non-endospore forming cells with coccoid or rod-shaped morphology (Collins et al., 1993; Björkroth et al., 2009, 2014) and belong to the group of bacteria generally known as lactic acid bacteria. Phylogenetically, the Weissella belong to the Firmicutes, class Bacilli, order Lactobacillales and family Leuconostocaceae (Collins et al., 1993). They are obligately heterofermentative, producing CO2 from carbohydrate metabolism with either D(−)-, or a mixture of D(−)- and L(+)- lactic acid and acetic acid as major end products from sugar metabolism. To date, there are 19 validly described Weissella species known. Weissella spp. have been isolated from and occur in a wide range of habitats, e.g., on the skin and in the milk and feces of animals, from saliva, breast milk, feces and vagina of humans, from plants and vegetables, as well as from a variety of fermented foods such as European sourdoughs and Asian and African traditional fermented foods. Thus, apart from a perceived technical role of certain Weissella species involved in such traditional fermentations, specific Weissella strains are also receiving attention as potential probiotics, and strain development of particularly W. cibaria strains is receiving attention because of their high probiotic potential for controlling periodontal disease. Moreover, W. confusa and W. cibaria strains are known to produce copius amounts of novel, non-digestible oligosaccharides and extracellular polysaccharides, mainly dextran. These polymers are receiving increased attention for their potential application as prebiotics and for a wide range of industrial applications, predominantly for bakeries and for the production of cereal-based fermented functional beverages. On the detrimental side, strains of certain Weissella species, e.g., of W. viridescens, W. cibaria and W. confusa, are known as opportunistic pathogens involved in human infections while strains of W. ceti have been recently recongnized as etiological agent of “weissellosis,” which is a disease affecting farmed rainbow trouts. Bacteria belonging to this species thus are important both from a technological, as well as from a medical point of view, and both aspects should be taken into account in any envisaged biotechnological applications.
Full-text · Article · Feb 2015 · Frontiers in Microbiology
[Show abstract][Hide abstract] ABSTRACT: Introduction
Non alcoholic fatty liver disease (NAFLD), defined by accumulation of triglycerides in hepatocytes in the absence of alcohol consumption, is associated with obesity. Evidences so far suggest that ethanol produced by gut microbial strains may be implicated in this metabolic disease.
In vitro fermentation under anaerobic conditions in medium for colonic bacteria (MCB), supplemented with fructose, was applied for evaluating metabolite profiles of the heterofermentative lactic acid bacteria (htLAB) Weissella confusa and Lactobacillus fermentum in absence or presence of sodium citrate, sodium pyruvate, ribose or xylose.
Results and Discussion
Results obtained showed that in the absence of electron acceptors (citrate, pyruvate), lactate was the major metabolite of W. confusa and L. fermentum. High amounts of ethanol were produced by W. confusa in MCB supplemented with fructose. In contrast, L. fermentum produced high amounts of mannitol in the same medium. Lactate and acetate were the major metabolites of xylose or ribose fermentation by W. confusa and L. fermentum. Changes of fructose fermentation profiles were observed when citrate or pyruvate was added to the medium: besides lactate, succinate and acetate became the major metabolites of W. confusa and L. fermentum. Co-fermentation of both pentoses with fructose by W. confusa or L. fermentum resulted in decreased amounts of ethanol and increased amounts of lactate and acetate. Our data show that citrate and pyruvate may act as electron acceptors for NAD regeneration in htLAB resulting in decreased amounts of ethanol. Furthermore, fermentation by htLAB of pentoses instead of hexoses increases production of acetate at the expense of ethanol.
Consumption of natural sources or supplementation of diet with citrate, pyruvate or xylose could reduce production of ethanol by intestinal microbiota and thus may decrease the risk of NAFLD.
[Show abstract][Hide abstract] ABSTRACT: I. Einleitung
Nichtalkoholische Fettleber (NAFLD) ist definiert als „Fettanhäufung von Triglyceriden in 5 - 10% des Lebergewichts“ (Neuschwander-Teri & Caldwell, 2003) und mit Zeichen des metabolischen Syndroms assoziiert. Einige Studien legen nahe, dass die Darmmikrobiota, hauptsächlich Ethanol produzierende und Gram-negative Bakterien, für die Entwicklung der NAFLD eine Rolle spielen könnte (Nardone et al., 2004).
II. Ziele der Arbeit
In dieser Arbeit sollte untersucht werden, ob Elektronenakzeptoren (Natriumcitrat oder Natriumpyruvat) die Metaboliten-Profile ausgewählter Stämme der Darmflora und von Probiotika verändern können und inwieweit sich hierin Bakterien unterscheiden.
Bakterielle Fermentationen wurden in Wachstumsmedium unter Sauerstoffausschluss durchgeführt. Metabolitenprofile wurden mittels HPLC analysiert.
• Lactobacillus fermentum produziert große Mengen an Ethanol aus Glukose und an Mannit aus Fruktose.
• Weissella confusa (Isolat aus menschlichen Darm) produziert große Mengen an Ethanol aus Monosacchariden (Glukose oder Fruktose).
• Bei Zusatz von Natriumcitrat oder Natriumpyruvat zu Wachstumsmedium, änderten sich die Metaboliten-Profile erheblich.
• Neben Laktat stellten Succinat und Acetat die Hauptmetaboliten für W. confusa und L. fermentum bei Zusatz von Citrat oder Pyruvat dar.
Supplementierung mit Citrat oder Pyruvat konnte die Produktion von Ethanol durch Stämme der Darmflora reduzieren. Im Fall des L. fermentum führte der Austausch von Glukose gegen Fruktose zur Verringerung der Ethanol Produktion. Mögliche Implikationen für die NAFLD werden diskutiert.
[Show abstract][Hide abstract] ABSTRACT: The fate of 5 different Escherichia coli strains, including 3 Shiga toxin-producing E. coli (STEC) strains, was analyzed during the production and ripening of semihard raw milk cheese. The strains, which were previously isolated from raw milk cheese, were spiked into raw milk before cheese production at 2 different levels (approximately 10(1) and 10(3) cfu/mL, respectively). Two cheese types were produced, which differed in cooking temperatures (40 and 46°C). The cheeses were sampled during manufacture and the 16-wk ripening period. An increase in E. coli counts of approximately 3.5 log(10) cfu/g occurred from raw milk to fresh cheese at d 1, which was attributed to a concentration effect during cheese production and growth of the strains. During ripening over 16 wk, a slow, continuous decrease was observed for all strains. However, significant differences were found between the E. coli strains at the applied spiking levels, whereas the inactivation was similar in the 2 different cheese types. The 2 generic E. coli strains survived at higher counts than did the 3 STEC strains. Nevertheless, only 1 of the 3 STEC strains showed significantly weaker survival at both spiking levels and in both cheese types. Six of 16 cheeses made from raw milk at a low spiking level contained more than 10 cfu/g of STEC at the end of the 16-wk ripening process. After enrichment, STEC were detected in almost all cheeses at both spiking levels. Particularly because of the low infectious dose of highly pathogenic STEC, even low colony counts in raw milk cheese are a matter of concern.
Full-text · Article · Dec 2012 · Journal of Dairy Science
[Show abstract][Hide abstract] ABSTRACT: People suffering from non-alcoholic fatty liver disease (NAFLD) show - without any consumption of
alcohol - all signs of a typical alcohol-induced fatty liver. So far the elicitor of NAFLD remains
unclear. However, alcohol produced by the intestinal microbiota has been discussed to be involved
in the development of the disease. In order to take a closer look at this problem, a simple
fermentation model was established for evaluating strains intestinal and lactic acid bacteria. So far,
we analysed Anaerostipes caccae, Bacteroides thetaiotamicron, Bifidobacterium longum,
Escherichia coli, Lactobacillus acidophilus, Lactobacillus fermentum, Lactobacillus plantarum and
Lactobacillus reuteri with respect to their metabolic activities. Medium for colonic bacteria (MCB),
supplemented with different sugars like glucose, fructose, lactulose, arabinose, ribose and inulin
was used under anaerobic conditions.The results obtained generally reflected the anticipated
metabolic activities. Lactate was the major metabolite for all lactobacilli strains. High amounts of
ethanol were observed in L. fermentum and L. reuteri, grown in MCB supplemented with either
glucose or fructose. Lactate and acetate were the major metabolites of B. longum, however
succinate and acetate were the major metabolic substances of B. thetaiotamicron. On the other
hand, butyrate was only the major metabolite of A. caccae in all tested sugars except inulin. E. coli
showed mixed acid fermentation with different amount of ethanol from all tested sugars except
inulin. Fermentation of lactulose and inulin, two potential prebiotics, could reduce the production
of ethanol by the intestinal bacteria. We now plan to conduct co-fermentation experiments to see,
whether combinations of different bacteria will change the overall metabolic profiles in general and
the production of ethanol in particular.
Key words: lactobacilli, Bacteroides thetaiotamicron, fructose, prebiotic, probiotic, intestinal microbiota
[Show abstract][Hide abstract] ABSTRACT: The aim of this work was to investigate how production and freeze-drying conditions of Bifidobacterium animalis subsp. lactis INL1, a probiotic strain isolated from breast milk, affected its survival and resistance to simulated gastric digestion during storage in food matrices. The determination of the resistance of bifidobacteria to simulated gastric digestion was useful for unveiling differences in cell sensitivity to varying conditions during biomass production, freeze-drying and incorporation of the strain into food products. These findings show that bifidobacteria can become sensitive to technological variables (biomass production, freeze-drying and the food matrix) without this fact being evidenced by plate counts.
No preview · Article · May 2012 · Food Microbiology
[Show abstract][Hide abstract] ABSTRACT: Screening of 175 yeasts in an agar plate co-cultivation assay revealed that five out of 31 species reduced Listeria monocytogenes by 4–5 log units, one exceptionally active Pichia norvegensis reduced Listeria by 7 log units. To test the anti-listerial activity of this Pichia strain on cheese, Tilsit cheese and smeared acid curd cheese (Harzer) were prepared. The Tilsit cheese surface was inoculated with a 3%-NaCl brine containing Brevibacterium linens, Microbacterium gubbeenense, Corynebacterium casei, Staphylococcus equorum, Debaryomyces hansenii, P. norvegensis and L. monocytogenes. Ripening was done at 13 °C and >95% relative humidity. On the Tilsit, but not on the Harzer cheeses, a decrease of listerial cell numbers by 1–2 log units was observed. The difference between high inhibition in agar plate co-cultivation versus cheese is probably due to a decreased expression of the unknown inhibitory substance due to lactate, but not by the low pH.
Full-text · Article · Feb 2011 · International Dairy Journal
[Show abstract][Hide abstract] ABSTRACT: The objective of the study was to isolate potential probiotic lactobacilli from Kimere, a pearl millet dough prepared in the Mbeere community of Kenya, East Africa, by fermentation for 18-24 hours. Kimere samples, collected from 11 different homesteads in Mbeere, showed average pH values of 3.63±0.29. Counts of presumptive lactobacilli were 8.52±0.02 log10 colony forming units per gram, respectively. 48 presumptive Lactobacillus isolates were characterised and identified by biochemical and molecular methods. Lactobacillus fermentum (46 isolates) was the dominant Lactobacillus species detected. Analysis of strain diversity with pulsed-field gel electrophoresis indicated relatively large biodiversity among L. fermentum isolates. All L. fermentum isolates were able to grow in MRS medium containing 0.3% ox gall. Twelve of them were able to grow in the presence of 3% ox gall, and of these 60% survived incubation at pH 3 in the presence of 2 mg pepsin per ml for three hours.
No preview · Article · Sep 2010 · Beneficial Microbes
[Show abstract][Hide abstract] ABSTRACT: IntroductionSurface-ripened cheesesClassification of secondary starter culturesCommercially available secondary cheese starter culturesSurface ripeningDevelopment of defined surface starter culturesProteolysis and lipolysisAromaConclusions
[Show abstract][Hide abstract] ABSTRACT: Upon growth in modified milk medium of pure cultures of micro-organisms involved in surface-ripening of red-smear cheese (Brevibacterium linens, Corynebacterium casei, Corynebacterium variabile, Arthrobacter nicotianae, Microbacterium gubbeenense, Staphylococcus equorum, S. xylosus, Debaryomyces hansenii, Geotrichum candidum), degradation of casein in the growth medium was observed. To differentiate whether extracellular or intracellular enzymes were responsible for degradation, Na-caseinate was incubated with either supernatant medium after growth and removal of micro-organisms or with cell-free extract obtained by disintegration of cells. Our results show that B. linens, A. nicotianae and M. gubbeenense apparently produce extracellular enzymes involved in casein degradation, while G. candidum produces intracellular enzymes efficiently degrading casein after cell lysis.
Full-text · Article · Jan 2009 · Milchwissenschaft
[Show abstract][Hide abstract] ABSTRACT: Amplified ribosomal DNA restriction analysis was used for classification of 90 yeast strains of 32 species of dairy origin. Primers ITS1 and ITS4 yielded PCR products in the range 375bp (Candida lipolytica) to 915bp (Schizosaccharomyces pombe). Species-specific restriction products were liberated by the enzymes Hin6I, HinfI and BsuRI. Some species showed genetic variation, leading to PCR products of different sizes (Debaryomyces hansenii, C. lipolytica, Candida inconspicua, Candida sake). Restriction patterns of three Trichosporon species were similar; a species determination was possible by including Trichosporon reference strains on the gels. Candida krusei, an essential ripening culture of acid curd cheese, could be distinguished from Candida norvegensis and C. inconspicua. C. lipolytica, an important contaminant of smear cheeses, could be classified by the size of the PCR product and restriction patterns. The method provides a fast and reliable tool for identification of dairy yeasts. Size determination of the PCR products gives a narrow range of possible species, while subsequent restriction analysis allows accurate species classification of relevant dairy yeasts.
Full-text · Article · Oct 2008 · International Dairy Journal
[Show abstract][Hide abstract] ABSTRACT: In this communication, we describe the isolation of a Lactobacillus delbrueckii subsp. bulgaricus 92063 mutant strain named pH-P11, which differed from the parent strain by low proteolytic activity and altered regulation of expression of lacZ in the presence of glucose or lactose. In the presence of lactose, beta-galactosidase activity was approximately twice as high in pH-P11 than in the wild type. pH-P11 exhibited protosymbiosis together with Streptococcus thermophilus. Yoghurt produced with pH-P11 was characterized by low acidity and little post-acidification during storage. The organoleptic properties (absence of bitterness and other off-flavors, weak sourness, and clear yoghurt taste) were those of a typical "yoghurt mild". This mild flavor was achieved at rather high cell counts of lactobacilli even at the end of shelf-life. High cell counts in conjunction with high beta-galactosidase activity make pH-P11 an interesting strain for application in yoghurt especially designed for consumers with lactose malabsorption. In contrast to "yoghurt mild", which is predominantly produced with Lactobacillus acidophilus together with Streptococcus thermophilus, the product obtained by fermentation with pH-P11 and Streptococcus thermophilus concurs with international standards for yoghurt. During frequent sub-culturing, strain pH-P11, which is supposed to differ from the wild type by one or a few so-far-not-characterized mutations, showed sufficient stability for application in industrial production.
No preview · Article · Apr 2007 · Biotechnology Journal