Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 1.101
Filtrar
1.
Appl Environ Microbiol ; 86(14)2020 07 02.
Artigo em Inglês | MEDLINE | ID: mdl-32414802

RESUMO

Bioethanol production from syngas using acetogenic bacteria has attracted considerable attention in recent years. However, low ethanol yield is the biggest challenge that prevents the commercialization of syngas fermentation into biofuels using microbial catalysts. The present study demonstrated that ethanol metabolism plays an important role in recycling NADH/NAD+ during autotrophic growth. Deletion of bifunctional aldehyde/alcohol dehydrogenase (adhE) genes leads to significant growth deficiencies in gas fermentation. Using specific fermentation technology in which the gas pressure and pH were constantly controlled at 0.1 MPa and 6.0, respectively, we revealed that ethanol was formed during the exponential phase, closely accompanied by biomass production. Then, ethanol was oxidized to acetate via the aldehyde ferredoxin oxidoreductase pathway in Clostridium ljungdahlii A metabolic experiment using 13C-labeled ethanol and acetate, redox balance analysis, and comparative transcriptomic analysis demonstrated that ethanol production and reuse shared the metabolic pathway but occurred at different growth phases.IMPORTANCE Ethanol production from carbon monoxide (CO) as a carbon and energy source by Clostridium ljungdahlii and "Clostridium autoethanogenum" is currently being commercialized. During gas fermentation, ethanol synthesis is NADH-dependent. However, ethanol oxidation and its regulatory mechanism remain incompletely understood. Energy metabolism analysis demonstrated that reduced ferredoxin is the sole source of NADH formation by the Rnf-ATPase system, which provides ATP for cell growth during CO fermentation. Therefore, ethanol production is tightly linked to biomass production (ATP production). Clarification of the mechanism of ethanol oxidation and biosynthesis can provide an important reference for generating high-ethanol-yield strains of C. ljungdahlii in the future.


Assuntos
Biocombustíveis/microbiologia , Monóxido de Carbono/metabolismo , Clostridium/metabolismo , Etanol/metabolismo , Processos Autotróficos , Clostridium/crescimento & desenvolvimento , Fermentação
2.
Artigo em Inglês | MEDLINE | ID: mdl-32403297

RESUMO

A variety of activities potentially contribute to the beneficial effects of probiotic bacteria observed in humans. Among these is a direct inhibition of the growth of pathogenic bacteria in the gut. The present study characterizes head-to-head the in-vitro pathogen growth inhibition of clinically relevant infectious bacterial strains by different types of probiotics and a synbiotic. In-vitro growth inhibition of Escherichia (E.) coli EPEC, Shigella (Sh.) sonnei, Salmonella (S.) typhimurium, Klebsiella (K.) pneumoniae and Clostridioides (C.) difficile were determined. Investigated products were a yeast mono strain probiotic containing Saccharomyces (Sac.) boulardii, bacterial mono strain probiotics containing either Lactobacillus (L.) rhamnosus GG or L. reuteri DSM 17938, a multi strain probiotic containing three L. rhamnosus strains (E/N, Oxy, Pen), and a multi strain synbiotic containing nine different probiotic bacterial strains and the prebiotic fructooligosaccharides (FOS). Inhibition of pathogens was moderate by Sac. boulardii and L. rhamnosus GG, medium by L. reuteri DSM 17938 and the L. rhamnosus E/N, Oxy, Pen mixture and strong by the multi strain synbiotic. Head-to-head in-vitro pathogen growth inhibition experiments can be used to differentiate products from different categories containing probiotic microorganisms and can support the selection process of products for further clinical evaluation.


Assuntos
Clostridium/crescimento & desenvolvimento , Enterobacteriaceae/crescimento & desenvolvimento , Lactobacillus/fisiologia , Probióticos , Saccharomyces/fisiologia , Simbióticos , Antibiose , Clostridium/patogenicidade , Enterobacteriaceae/patogenicidade , Humanos , Oligossacarídeos , Prebióticos
3.
Curr Issues Mol Biol ; 38: 103-122, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31967578

RESUMO

Five bacterial (facultatively) anaerobic strains, namely Buttiauxella sp. MASE-IM-9, Clostridium sp. MASE-IM-4, Halanaerobium sp. MASE-BB-1, Trichococcus sp. MASE-IM-5, and Yersinia intermedia MASE-LG-1 isolated from different extreme natural environments were subjected to Mars relevant environmental stress factors in the laboratory under controlled conditions. These stress factors encompassed low water activity, oxidizing compounds, and ionizing radiation. Stress tests were performed under permanently anoxic conditions. The survival rate after addition of sodium perchlorate (Na-perchlorate) was found to be species-specific. The inter-comparison of the five microorganisms revealed that Clostridium sp. MASE-IM-4 was the most sensitive strain (D10-value (15 min, NaClO4) = 0.6 M). The most tolerant microorganism was Trichococcus sp. MASE-IM-5 with a calculated D10-value (15 min, NaClO4) of 1.9 M. Cultivation in the presence of Na-perchlorate in Martian relevant concentrations up to 1 wt% led to the observation of chains of cells in all strains. Exposure to Na-perchlorate led to a lowering of the survival rate after desiccation. Consecutive exposure to desiccating conditions and ionizing radiation led to additive effects. Moreover, in a desiccated state, an enhanced radiation tolerance could be observed for the strains Clostridium sp. MASE-IM-4 and Trichococcus sp. MASE-IM-5. These data show that anaerobic microorganisms from Mars analogue environments can resist a variety of Martian-simulated stresses either individually or in combination. However, responses were species-specific and some Mars-simulated extremes killed certain organisms. Thus, although Martian stresses would be expected to act differentially on microorganisms, none of the expected extremes tested here and found on Mars prevent the growth of anaerobic microorganisms.


Assuntos
Bactérias Anaeróbias/crescimento & desenvolvimento , Meio Ambiente Extraterreno , Ambientes Extremos , Bactérias Anaeróbias/efeitos dos fármacos , Bactérias Anaeróbias/efeitos da radiação , Carnobacteriaceae/efeitos dos fármacos , Carnobacteriaceae/crescimento & desenvolvimento , Carnobacteriaceae/efeitos da radiação , Sobrevivência Celular/efeitos dos fármacos , Sobrevivência Celular/efeitos da radiação , Clostridium/efeitos dos fármacos , Clostridium/crescimento & desenvolvimento , Clostridium/efeitos da radiação , Dessecação , Enterobacteriaceae/efeitos dos fármacos , Enterobacteriaceae/crescimento & desenvolvimento , Enterobacteriaceae/efeitos da radiação , Firmicutes/efeitos dos fármacos , Firmicutes/crescimento & desenvolvimento , Firmicutes/efeitos da radiação , Marte , Estresse Oxidativo , Percloratos/toxicidade , Tolerância a Radiação , Compostos de Sódio/toxicidade , Estresse Fisiológico/efeitos da radiação , Fatores de Tempo , Yersinia/efeitos dos fármacos , Yersinia/crescimento & desenvolvimento , Yersinia/efeitos da radiação
4.
Microbiol Spectr ; 7(6)2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-31858953

RESUMO

As obligate anaerobes, clostridial pathogens depend on their metabolically dormant, oxygen-tolerant spore form to transmit disease. However, the molecular mechanisms by which those spores germinate to initiate infection and then form new spores to transmit infection remain poorly understood. While sporulation and germination have been well characterized in Bacillus subtilis and Bacillus anthracis, striking differences in the regulation of these processes have been observed between the bacilli and the clostridia, with even some conserved proteins exhibiting differences in their requirements and functions. Here, we review our current understanding of how clostridial pathogens, specifically Clostridium perfringens, Clostridium botulinum, and Clostridioides difficile, induce sporulation in response to environmental cues, assemble resistant spores, and germinate metabolically dormant spores in response to environmental cues. We also discuss the direct relationship between toxin production and spore formation in these pathogens.


Assuntos
Infecções por Clostridium/microbiologia , Clostridium/crescimento & desenvolvimento , Esporos Bacterianos/crescimento & desenvolvimento , Animais , Clostridium/classificação , Clostridium/genética , Clostridium/patogenicidade , Humanos , Esporos Bacterianos/classificação , Esporos Bacterianos/genética , Esporos Bacterianos/metabolismo
5.
Microbiologyopen ; 8(10): e872, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31568706

RESUMO

The number of agricultural biogas plants has been increasing in the past decades in some European countries. Digestates obtained after anaerobic digestion (AD) of manure are usually spread on agricultural land; however, their hygiene status regarding pathogens posing public health and/or animal health challenges has been poorly characterized up to now in France. In this study, three replicates of manure and digestate were collected from five farm biogas plants receiving animal manure in order to assess the occurrence and concentrations of sporulating (Clostridium botulinum, Clostridioides difficile, Clostridium perfringens) and nonsporulating (Listeria monocytogenes, thermotolerant Campylobacter spp., Salmonella, Escherichia coli, enterococci) bacteria. Concentrations of E. coli, enterococci, and C. perfringens in digestates ranged from 102 to 104 , 104 to 105 , and <103 to 7 × 105  CFU/g, respectively. Salmonella and C. difficile were detected in manure and digestate from the five biogas plants at concentrations ranging from <1.3 to >7 × 102  MPN/g and from 1.3 to 3 × 102  MPN/g, respectively. Thermotolerant Campylobacter, detected in all the manures, was only found in two digestates at a concentration of cells ranging from <10 to 2.6 × 102  CFU/g. Listeria monocytogenes and C. botulinum were detected in three manures and four digestates. The bacterial counts of L. monocytogenes and C. botulinum did not exceed 3 × 102 and 14 MPN/g, respectively. C. botulinum type B was detected at very low level in both the manure and digestate of farm biogas plants with no botulism history. The levels of pathogenic bacteria in both manure and digestate suggested that some bacteria can persist throughout AD.


Assuntos
Clostridium/isolamento & purificação , Enterobacteriaceae/isolamento & purificação , Listeria monocytogenes/isolamento & purificação , Esterco/microbiologia , Biocombustíveis/microbiologia , Clostridium/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Enterobacteriaceae/crescimento & desenvolvimento , França , Listeria monocytogenes/crescimento & desenvolvimento , Esporos Bacterianos/crescimento & desenvolvimento
6.
Food Microbiol ; 84: 103244, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31421772

RESUMO

Today, there is no effective non-thermal method to inactivate unwanted bacterial spores in foods. High-Pressure (HP) process has been shown to act synergistically with moderate heating and the bacteriocin nisin to inactivate spores but the mechanisms have not been elucidated. The purpose of the present work was to investigate in depth the synergy of HP and nisin on various foodborne spore species and to bring new elements of understandings. For this purpose, spores of Bacillus pumilus, B. sporothermodurans, B. licheniformis, B. weihenstephanensis, and Clostridium sp. were suspended in MES buffer, in skim milk or in a liquid medium simulating cooked ham brine and treated by HP at 500 MPa for 10 min at 50 °C or 20 °C. Nisin (20 or 50 IU/mL) was added at three different points during treatment: during HP, during and or in the plating medium of enumeration. In the latter two cases, a high synergy was observed with the inhibition of the spores of Bacillus spp. The evaluation of the germinated fraction of Bacillus spp. spores after HP revealed that this synergy was likely due to the action of nisin on HP-sensitized spores, rather than on HP-germinated spores. Thus, the combination of nisin and HP can lead to Bacillus spp. spore inhibition at 20 °C. And Nisin can act on HP-treated spores, even if they are not germinated. This paper provides new information about the inhibition of spores by the combination of HP and nisin. The high synergy observed at low temperature has not been reported yet and could allow food preservation without the use of any thermal process.


Assuntos
Pressão Atmosférica , Viabilidade Microbiana/efeitos dos fármacos , Nisina/farmacologia , Esporos Bacterianos/efeitos dos fármacos , Bacillus/efeitos dos fármacos , Bacillus/crescimento & desenvolvimento , Clostridium/efeitos dos fármacos , Clostridium/crescimento & desenvolvimento , Conservação de Alimentos , Temperatura Alta
7.
Appl Microbiol Biotechnol ; 103(11): 4633-4648, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30972463

RESUMO

Clostridium autoethanogenum and Clostridium ljungdahlii are physiologically and genetically very similar strict anaerobic acetogens capable of growth on carbon monoxide as sole carbon source. While exact nutritional requirements have not been reported, we observed that for growth, the addition of vitamins to media already containing yeast extract was required, an indication that these are fastidious microorganisms. Elimination of complex components and individual vitamins from the medium revealed that the only organic compounds required for growth were pantothenate, biotin and thiamine. Analysis of the genome sequences revealed that three genes were missing from pantothenate and thiamine biosynthetic pathways, and five genes were absent from the pathway for biotin biosynthesis. Prototrophy in C. autoethanogenum and C. ljungdahlii for pantothenate was obtained by the introduction of plasmids carrying the heterologous gene clusters panBCD from Clostridium acetobutylicum, and for thiamine by the introduction of the thiC-purF operon from Clostridium ragsdalei. Integration of panBCD into the chromosome through allele-coupled exchange also conveyed prototrophy. C. autoethanogenum was converted to biotin prototrophy with gene sets bioBDF and bioHCA from Desulfotomaculum nigrificans strain CO-1-SRB, on plasmid and integrated in the chromosome. The genes could be used as auxotrophic selection markers in recombinant DNA technology. Additionally, transformation with a subset of the genes for pantothenate biosynthesis extended selection options with the pantothenate precursors pantolactone and/or beta-alanine. Similarly, growth was obtained with the biotin precursor pimelate combined with genes bioYDA from C. acetobutylicum. The work raises questions whether alternative steps exist in biotin and thiamine biosynthesis pathways in these acetogens.


Assuntos
Clostridium/crescimento & desenvolvimento , Clostridium/metabolismo , Engenharia Metabólica/métodos , Redes e Vias Metabólicas/genética , Vitaminas/biossíntese , Clostridium/genética , Meios de Cultura/química , Desulfotomaculum/genética , Expressão Gênica , Genes Bacterianos , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo
8.
PLoS Comput Biol ; 15(3): e1006848, 2019 03.
Artigo em Inglês | MEDLINE | ID: mdl-30845144

RESUMO

The unique capability of acetogens to ferment a broad range of substrates renders them ideal candidates for the biotechnological production of commodity chemicals. In particular the ability to grow with H2:CO2 or syngas (a mixture of H2/CO/CO2) makes these microorganisms ideal chassis for sustainable bioproduction. However, advanced design strategies for acetogens are currently hampered by incomplete knowledge about their physiology and our inability to accurately predict phenotypes. Here we describe the reconstruction of a novel genome-scale model of metabolism and macromolecular synthesis (ME-model) to gain new insights into the biology of the model acetogen Clostridium ljungdahlii. The model represents the first ME-model of a Gram-positive bacterium and captures all major central metabolic, amino acid, nucleotide, lipid, major cofactors, and vitamin synthesis pathways as well as pathways to synthesis RNA and protein molecules necessary to catalyze these reactions, thus significantly broadens the scope and predictability. Use of the model revealed how protein allocation and media composition influence metabolic pathways and energy conservation in acetogens and accurately predicted secretion of multiple fermentation products. Predicting overflow metabolism is of particular interest since it enables new design strategies, e.g. the formation of glycerol, a novel product for C. ljungdahlii, thus broadening the metabolic capability for this model microbe. Furthermore, prediction and experimental validation of changing secretion rates based on different metal availability opens the window into fermentation optimization and provides new knowledge about the proteome utilization and carbon flux in acetogens.


Assuntos
Clostridium/metabolismo , Metais/metabolismo , Modelos Biológicos , Proteínas/metabolismo , Proteoma , Biocatálise , Carbono/metabolismo , Clostridium/genética , Clostridium/crescimento & desenvolvimento , Metabolismo Energético , Fermentação , Regulação Bacteriana da Expressão Gênica , Genes Bacterianos , Reprodutibilidade dos Testes
9.
Biotechnol Bioeng ; 116(7): 1627-1643, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-30825383

RESUMO

Microbial electrosynthesis or electro-fermentation in bioelectrochemical systems (BES) have recently received much attention. Here, we demonstrate with the glycerol metabolism by Clostridium pasteurianum that H 2 from in situ water electrolysis, especially in combination with a redox mediator, provides a simple and flexible way for shifting product selectivity and enhancing product yield in the fermentation process. In particular, we report and quantify for the first time strictly different effects of Neutral Red (NR) and the barely studied redox mediator Brilliant Blue (BB) on the growth and product formation of C. pasteurianum grown on glycerol in a newly developed BES. We were able to switch the product formation pattern of C. pasteurianum with a concentration-dependent addition of NR and BB under varied iron availability. Interestingly, NR and BB influenced the glycerol metabolism in a strictly opposite manner concerning the formation of the major products 1,3-propanediol (1,3-PDO) and n-butanol (BuOH). Whereas, NR and iron generally enhance the formation of BuOH, BB favors the formation of 1,3-PDO. In BES the metabolic shifts were enhanced, leading to a further increased yield by as high as 33% for BuOH in NR fermentations and 21% for 1,3-PDO in BB fermentations compared with the respective controls. For the first time, the electron transfer mediated by these mediators and their recycle (recharge) were unambiguously quantified by excluding the overlapping effect of iron. BB has a higher capacity than NR and iron. The extra electron transfer by BB can account for as high as 30-75% of the total NAD + regeneration under certain conditions, contributing significantly to the product formation.


Assuntos
Reatores Biológicos , Clostridium/crescimento & desenvolvimento , Glicerol/metabolismo , Transporte de Elétrons , Oxirredução
10.
Nutrients ; 11(2)2019 Feb 21.
Artigo em Inglês | MEDLINE | ID: mdl-30795551

RESUMO

Many Clostridium species are found as commensal members of the intestinal microbiota. However, imbalances of the microbiota may lead to certain infections caused by these microorganisms, mainly Clostridium butyricum, Clostridium difficile, and Clostridium perfringens. In many cases, infection recurrence can occur after antibiotics, indicating the need for novel therapeutic options that act on the pathogens and also restore the microbiota. Herein, the in vitro antimicrobial activity and probiotic potential of clinical and reference strains of Bifidobacterium and Lactobacillus were investigated against Clostridium species. Antimicrobial activity was evaluated by the agar spot test and inhibition of gas production. Then, the probiotic potential of selected strains was assessed by analyzing their coaggregation ability, adhesive properties to host cells and mucin, tolerance to acidic pH and bile salts, and antimicrobial susceptibility profiles. Lactobacillus plantarum ATCC 8014 was the most promising strain based on its inhibitory activity against Clostridium spp. Also, this strain met criteria to be considered a probiotic based on its coaggregation ability, adhesive properties, and tolerance to harsh pH and bile acid salt conditions. The results indicate that among the studied strains, L. plantarum ATCC 8014 presents probiotic potential for controlling infections induced by the studied Clostridium species and should be further evaluated in in vivo animal models.


Assuntos
Bifidobacterium/crescimento & desenvolvimento , Infecções por Clostridium/microbiologia , Clostridium/crescimento & desenvolvimento , Microbioma Gastrointestinal , Lactobacillus/crescimento & desenvolvimento , Interações Microbianas , Probióticos , Anti-Infecciosos , Aderência Bacteriana , Ácidos e Sais Biliares , Infecções por Clostridium/tratamento farmacológico , Clostridium butyricum/crescimento & desenvolvimento , Clostridium perfringens/crescimento & desenvolvimento , Humanos , Concentração de Íons de Hidrogênio , Lactobacillus plantarum/crescimento & desenvolvimento , Testes de Sensibilidade Microbiana , Probióticos/uso terapêutico
11.
Int J Mol Sci ; 21(1)2019 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-31906096

RESUMO

Metabolic syndrome is a cluster of disorders that increase the risk of cardiovascular disease and diabetes. This study has investigated the responses to rind of yellow mangosteen (Garcinia dulcis), usually discarded as waste, in a rat model of human metabolic syndrome. The rind contains higher concentrations of phytochemicals (such as garcinol, morelloflavone and citric acid) than the pulp. Male Wistar rats aged 8-9 weeks were fed either corn starch diet or high-carbohydrate, high-fat diet for 16 weeks, which were supplemented with 5% freeze-dried G. dulcis fruit rind powder during the last 8 weeks. We characterised metabolic, cardiovascular, liver and gut microbiota parameters. High-carbohydrate, high-fat diet-fed rats developed abdominal obesity, hypertension, increased left ventricular diastolic stiffness, decreased glucose tolerance, fatty liver and reduced Bacteroidia with increased Clostridia in the colonic microbiota. G. dulcis fruit rind powder attenuated these changes, improved cardiovascular and liver structure and function, and attenuated changes in colonic microbiota. G. dulcis fruit rind powder may be effective in metabolic syndrome by appetite suppression, inhibition of inflammatory processes and increased fat metabolism, possibly related to changes in the colonic microbiota. Hence, we propose the use of G. dulcis fruit rind as a functional food to ameliorate symptoms of metabolic syndrome.


Assuntos
Colo , Carboidratos da Dieta/efeitos adversos , Gorduras na Dieta/efeitos adversos , Garcinia/química , Microbioma Gastrointestinal/efeitos dos fármacos , Síndrome Metabólica , Compostos Fitoquímicos , Animais , Bacteroides/classificação , Bacteroides/crescimento & desenvolvimento , Clostridium/classificação , Clostridium/crescimento & desenvolvimento , Colo/metabolismo , Colo/microbiologia , Carboidratos da Dieta/farmacologia , Gorduras na Dieta/farmacologia , Masculino , Síndrome Metabólica/induzido quimicamente , Síndrome Metabólica/tratamento farmacológico , Síndrome Metabólica/metabolismo , Síndrome Metabólica/microbiologia , Compostos Fitoquímicos/química , Compostos Fitoquímicos/farmacologia , Ratos , Ratos Wistar
12.
J Sci Food Agric ; 99(4): 1492-1500, 2019 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-30129042

RESUMO

BACKGROUND: Nitrite and hexamine are used as silage additives because of their adverse effects on Clostridia and Clostridia spores. The effect of sodium nitrite and sodium nitrite/hexamine mixtures on silage quality was investigated. A white lupin-wheat mixture was treated with sodium nitrite (NaHe0) (900 g t-1 forage), or mixtures of sodium nitrite (900 g t-1 ) and hexamine. The application rate of hexamine was 300 g t-1 (NaHe300) or 600 g t-1 (NaHe600). Additional treatments were the untreated control (Con), and formic acid (FA) applied at a rate of 4 L t-1 (1000 g kg-1 ). RESULTS: Additives improved silage quality noticeably only by reducing silage ammonia content compared with the control. The addition of hexamine to a sodium nitrite solution did not improve silage quality compared with the solution containing sodium nitrite alone. The increasing addition of hexamine resulted in linearly rising pH values (P < 0.001) and decreasing amounts of lactic acid (P < 0.01). Sodium nitrite based additives were more effective than formic acid in preventing butyric acid formation. Additives did not restrict the growth of Saccharomyces cerevisiae compared to the control. CONCLUSION: The addition of hexamine did not improve silage quality compared with a solution of sodium nitrite. © 2018 Society of Chemical Industry.


Assuntos
Clostridium/metabolismo , Aditivos Alimentares/análise , Lupinus/microbiologia , Metenamina/análise , Nitritos/análise , Saccharomyces cerevisiae/metabolismo , Silagem/análise , Triticum/microbiologia , Clostridium/crescimento & desenvolvimento , Fermentação , Aditivos Alimentares/metabolismo , Manipulação de Alimentos , Lupinus/química , Lupinus/metabolismo , Metenamina/metabolismo , Nitritos/metabolismo , Saccharomyces cerevisiae/crescimento & desenvolvimento , Silagem/microbiologia , Triticum/química , Triticum/metabolismo
13.
Lett Appl Microbiol ; 68(2): 142-148, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30444534

RESUMO

Arabinoxylans are part of dietary fibre and have received attention given their emergent prebiotic character. Four arabinoxylans extracts were obtained from Argentinian soft and hard wheat. In vitro assays were performed to describe the extent to which the extracts from whole wheat flour support selective growth of Bifidobacterium breve and probiotic Lactobacillus reuteri ATCC23272 in a defined media. The prebiotic effect was evaluated by three quantitative scores: relative growth, prebiotic activity score and prebiotic index. For prebiotic index equation the growth of Bacteroides and Clostridium strains was compared to that of bifidobacteria and lactic acid bacteria. All the arabinoxylans extracts supported the growth of Lactobacillus and Bifidobacterium, reaching higher prebiotic activity score values than inulin (0·37 and 0·36 for Lactobacillus and Bifidobacterium respectively). AX2 from soft wheat and AX4 from hard showed similar prebiotic index value to commercial inulin (2·64, 2·52 and 2·22 respectively), and AX3 extract presented higher prebiotic index value (4·09) than the positive control and other prebiotic index reported for arabinoxylans. These extracts could be used as prebiotic, synbiotic compositions or novel food prototypes to treat dysbiosis associated with many diseases. SIGNIFICANCE AND IMPACT OF THE STUDY: The present work demonstrates that AX extracts from Argentinian soft and hard wheat promote efficiently the growth of probiotic strain L. reuteri ATCC23272 and B. breve 286, validated with three different parameters that consider the growth of representative strains of Bacteria genera found in the gut. The evaluation of AX extracts as a food supplement in a murine model could confirm their ability to modulate the microbiome. Novel food prototypes including AX and probiotics could relieve local symptoms and may act as psychobiotics with a beneficial effect on microbiome-brain axis.


Assuntos
Bifidobacterium breve/crescimento & desenvolvimento , Lactobacillus reuteri/crescimento & desenvolvimento , Preparações de Plantas/farmacologia , Triticum/química , Xilanos/farmacologia , Bacteroides/crescimento & desenvolvimento , Clostridium/crescimento & desenvolvimento , Fibras na Dieta , Prebióticos/microbiologia , Probióticos/metabolismo , Simbióticos
14.
Food Microbiol ; 77: 21-25, 2019 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30297052

RESUMO

Predicting the microbial safety of food products stored in modified atmosphere packaging implies taking into account the effect of oxygen reduction on microbial growth. According to their respiratory-type, the micro-organisms are not impacted similarly by the oxygen concentration. The aim of this article was to quantify and model the oxygen effect on the growth rates of 5 bacterial species: Listeria monocytogenes and Bacillus weihenstephanensis (facultative anaerobic), Pseudomonas fluorescens (strict aerobic), Clostridium perfringens and Clostridium sporogenes (strict anaerobic). The results showed the oxygen concentration doesn't modify the behavior of both facultative anaerobic strains. The growth rate of P. fluorescens decreased with the oxygen concentration, but the effect is only noticeable when the oxygen concentration fell below 3% in the gaseous phase. Conversely, the oxygen acted as a growth inhibitor for both Clostridium species. But total inhibition is reached only for 3.26% and 6.61% respectively for C. sporogenes and C. perfringens. Two models have been fitted for both respiratory-types, the first is the Monod model considering oxygen as a substrate for growth, and the second is the classic inhibitory model based on minimal inhibitory concentration.


Assuntos
Bactérias/crescimento & desenvolvimento , Microbiologia de Alimentos , Modelos Biológicos , Oxigênio/metabolismo , Atmosfera , Bacillus/crescimento & desenvolvimento , Clostridium/crescimento & desenvolvimento , Clostridium perfringens/crescimento & desenvolvimento , Contagem de Colônia Microbiana , Embalagem de Alimentos , Cinética , Listeria monocytogenes/crescimento & desenvolvimento , Pseudomonas fluorescens/crescimento & desenvolvimento
15.
Biotechnol Bioeng ; 116(1): 28-40, 2019 01.
Artigo em Inglês | MEDLINE | ID: mdl-30267585

RESUMO

Gas fermentation has emerged as a technologically and economically attractive option for producing renewable fuels and chemicals from carbon monoxide (CO) rich waste streams. LanzaTech has developed a proprietary strain of the gas fermentating acetogen Clostridium autoethanogenum as a microbial platform for synthesizing ethanol, 2,3-butanediol, and other chemicals. Bubble column reactor technology is being developed for the large-scale production, motivating the investigation of multiphase reactor hydrodynamics. In this study, we combined hydrodynamics with a genome-scale reconstruction of C. autoethanogenum metabolism and multiphase convection-dispersion equations to compare the performance of bubble column reactors with and without liquid recycle. For both reactor configurations, hydrodynamics was predicted to diminish bubble column performance with respect to CO conversion, biomass production, and ethanol production when compared with bubble column models in which the gas phase was modeled as ideal plug flow plus axial dispersion. Liquid recycle was predicted to be advantageous by increasing CO conversion, biomass production, and ethanol and 2,3-butanediol production compared with the non-recycle reactor configuration. Parametric studies performed for the liquid recycle configuration with two-phase hydrodynamics showed that increased CO feed flow rates (more gas supply), smaller CO gas bubbles (more gas-liquid mass transfer), and shorter column heights (more gas per volume of liquid per time) favored ethanol production over acetate production. Our computational results demonstrate the power of combining cellular metabolic models and two-phase hydrodynamics for simulating and optimizing gas fermentation reactors.


Assuntos
Butileno Glicóis/metabolismo , Monóxido de Carbono/metabolismo , Clostridium/metabolismo , Etanol/metabolismo , Fermentação , Engenharia Metabólica , Reatores Biológicos/microbiologia , Clostridium/genética , Clostridium/crescimento & desenvolvimento , Hidrodinâmica
16.
Biotechnol Bioeng ; 116(2): 294-306, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30267586

RESUMO

Synthesis gas (syngas) fermentation via the Wood-Ljungdahl pathway is receiving growing attention as a possible platform for the fixation of CO 2 and renewable production of fuels and chemicals. However, the pathway operates near the thermodynamic limit of life, resulting in minimal adenosine triphosphate (ATP) production and long doubling times. This calls into question the feasibility of producing high-energy compounds at industrially relevant levels. In this study, we investigated the possibility of co-utilizing nitrate as an inexpensive additional electron acceptor to enhance ATP production during H 2 -dependent growth of Clostridium ljungdahlii, Moorella thermoacetica, and Acetobacterium woodii. In contrast to other acetogens tested, growth rate and final biomass titer were improved for C. ljungdahlii growing on a mixture of H 2 and CO 2 when supplemented with nitrate. Transcriptomic analysis, 13 CO 2 labeling, and an electron balance were used to understand how electron flux was partitioned between CO 2 and nitrate. We further show that, with nitrate supplementation, the ATP/adenosine diphosphate (ADP) ratio and acetyl-CoA pools were increased by fivefold and threefold, respectively, suggesting that this strategy could be useful for the production of ATP-intensive heterologous products from acetyl-CoA. Finally, we propose a pathway for enhanced ATP production from nitrate and use this as a basis to calculate theoretical yields for a variety of products. This study demonstrates a viable strategy for the decoupling of ATP production from carbon dioxide fixation, which will serve to significantly improve the CO 2 fixation rate and the production metrics of other chemicals from CO 2 and H 2 in this host.


Assuntos
Acetobacterium/metabolismo , Dióxido de Carbono/metabolismo , Clostridium/metabolismo , Hidrogênio/metabolismo , Moorella/metabolismo , Nitratos/metabolismo , Acetobacterium/crescimento & desenvolvimento , Trifosfato de Adenosina/biossíntese , Ciclo do Carbono , Clostridium/crescimento & desenvolvimento , Análise do Fluxo Metabólico , Moorella/crescimento & desenvolvimento
17.
Gut Microbes ; 10(4): 481-503, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-30589376

RESUMO

The human gut hosts trillions of microorganisms that exert a profound influence on human biology. Gut bacteria communicate with their host by secreting small molecules that can signal to distant organs in the body. Bile acids are one class of these signaling molecules, synthesized by the host and chemically transformed by the gut microbiota. Among bile acid metabolizers, bile acid 7-dehydroxylating bacteria are commensals of particular importance as they carry out the 7-dehydroxylation of liver-derived primary bile acids to 7-dehydroxylated bile acids. The latter represents a major fraction of the secondary bile acid pool. The microbiology of this group of gut microorganisms is understudied and warrants more attention. Here, we detail the bile acid transformations carried out by the 7-dehydroxylating bacterium Clostridium scindens in vitro and in vivo. In vitro, C. scindens exhibits not only 7α-dehydroxylating capabilities but also, the ability to oxidize other hydroxyl groups and reduce ketone groups in primary and secondary bile acids. This study revealed 12-oxolithocholic acid as a major transient product in the 7α-dehydroxylation of cholic acid. Furthermore, the in vivo study included complementing a gnotobiotic mouse line (devoid of the ability to 7-dehydroxylate bile acids) with C. scindens and investigating its colonization dynamics and bile acid transformations. Using NanoSIMS (Nanoscale Secondary Ion Mass Spectrometry), we demonstrate that the large intestine constitutes a niche for C. scindens, where it efficiently 7-dehydroxylates cholic acid to deoxycholic acid. Overall, this work reveals a novel transient species during 7-dehydroxylation as well as provides direct evidence for the colonization and growth of 7-dehydroxylating bacteria in the large intestine.


Assuntos
Ácidos e Sais Biliares/metabolismo , Clostridium/metabolismo , Trato Gastrointestinal/microbiologia , Animais , Ácidos e Sais Biliares/química , Biotransformação , Clostridium/crescimento & desenvolvimento , Ácido Desoxicólico/química , Ácido Desoxicólico/metabolismo , Trato Gastrointestinal/química , Vida Livre de Germes , Humanos , Ácido Litocólico/química , Ácido Litocólico/metabolismo , Masculino , Camundongos , Estrutura Molecular
18.
Nat Commun ; 9(1): 4474, 2018 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-30367068

RESUMO

Control of translation is vital to all species. Here we employ a multi-omics approach to decipher condition-dependent translational regulation in the model acetogen Clostridium ljungdahlii. Integration of data from cells grown autotrophically or heterotrophically revealed that pathways critical to carbon and energy metabolism are under strong translational regulation. Major pathways involved in carbon and energy metabolism are not only differentially transcribed and translated, but their translational efficiencies are differentially elevated in response to resource availability under different growth conditions. We show that translational efficiency is not static and that it changes dynamically in response to mRNA expression levels. mRNAs harboring optimized 5'-untranslated region and coding region features, have higher translational efficiencies and are significantly enriched in genes encoding carbon and energy metabolism. In contrast, mRNAs enriched in housekeeping functions harbor sub-optimal features and have lower translational efficiencies. We propose that regulation of translational efficiency is crucial for effectively controlling resource allocation in energy-deprived microorganisms.


Assuntos
Carbono/metabolismo , Clostridium/metabolismo , Metabolismo Energético/genética , Regulação Bacteriana da Expressão Gênica , Biossíntese de Proteínas , Processos Autotróficos/genética , Clostridium/genética , Clostridium/crescimento & desenvolvimento , Perfilação da Expressão Gênica , Processos Heterotróficos/genética , Redes e Vias Metabólicas , Proteômica , RNA Mensageiro/classificação , RNA Mensageiro/genética , Transcrição Genética
19.
J Biotechnol ; 286: 71-78, 2018 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-30205138

RESUMO

Cashew apple bagasse (CAB) has been studied as feedstock for the biohydrogen production using Clostridium roseum and the dark fermentation process. Pretreatment with alkaline hydrogen peroxide (CAB-AHP) on raw material and the acid and enzymatic hydrolysis have been taken into account to evaluate the H2 yields. Results show that the acid hydrolysate obtained from CAB produced higher H2 molar yield (HMY) (15 mmolH2/Lhydrolysate) than the acid hydrolysate from CAB-AHP (4.99 mmolH2/Lhydrolysate), These HMY were noticeably higher than values obtained from the enzymatic hydrolysate of CAB-AHP (1.05 mmolH2/Lhydrolysa) and the enzymatic hydrolysate of CAB (0.59 mmolH2/Lhydrolysa). The maximum biohydrogen productivity (12.57 mLH2/L.h) was achieved using the acid hydrolysate from CAB, with a H2 content of about 72% vol, that could be satisfactory in view of an energetic applications of the biogas. Results suggest that CAB could be considered for the hydrogen production process, providing an appropriate destination for this lignocellulosic biomass, and consequently, reducing the environmental impact it can exert.


Assuntos
Anacardium/química , Celulose/química , Clostridium/crescimento & desenvolvimento , Hidrogênio/metabolismo , Anacardium/efeitos dos fármacos , Biomassa , Clostridium/metabolismo , Fermentação , Peróxido de Hidrogênio/farmacologia , Hidrólise
20.
Int J Food Microbiol ; 286: 148-154, 2018 Dec 02.
Artigo em Inglês | MEDLINE | ID: mdl-30114563

RESUMO

The effect of storage temperature and time on the viability of several foodborne bacterial pathogens inoculated into vacuum-packed canned pasteurized cow's milk cheese was investigated. Three popular cheese styles namely, a semi-soft white Monterey Jack style cheese, and two Cheddar cheeses vacuum packaged in mason jars were inoculated with a 3-strain cocktail of each of the following microbes at the mean concentrations listed: Escherichia coli O157:H7 (6.6 log CFU/g), Salmonella spp. (6.3 log CFU/g), Listeria innocua (6.4 log CFU/g), Staphylococcus aureus (3.6 log CFU/g), and Clostridium sporogenes vegetative cells (6.3 log CFU/g), and spores (6.0 log CFU/g). The effect of storage temperature (at 4.4, 10, and 21.1 °C) and the time (from 0 to 365 days) on the survival of the inoculated organisms was evaluated at different sampling times (0, 30, 60, 120,180, and 365 days). Both storage temperature and the time had a significant effect on the viability of the test organisms. Increasing the storage temperature from 4.4 to 21.1 °C and the storage time for up to 365 days increased pathogen reduction. The type of cheese also had a significant effect on the viability of the test organisms. At the same sampling times, the viability of E. coli O157:H7 and Salmonella spp., were highest in Monterey Jack-style cheese followed by the Cheddar cheeses one to which annatto had been added (Cheddar 1) and the second, a white Cheddar that has an added adjunct flavor culture (Cheddar 2). Similarly, the type of cheese and the time-temperature conditions to which the cheese was exposed had a significant effect on the viability of L. innocua. Among the tested organisms, S. aureus was most susceptible while C. sporogenes (both vegetative cells and spores) were most resistant. The findings of this challenge study indicate that vacuum packed canned cheese is not a favorable environment for the growth of bacterial pathogens. Depending upon the type of canned cheese, appropriate storage times and temperatures are critical to ensure microbiological safety.


Assuntos
Queijo/microbiologia , Clostridium/crescimento & desenvolvimento , Escherichia coli O157/crescimento & desenvolvimento , Listeria monocytogenes/crescimento & desenvolvimento , Listeria/crescimento & desenvolvimento , Salmonella/crescimento & desenvolvimento , Esporos Bacterianos/crescimento & desenvolvimento , Staphylococcus aureus/crescimento & desenvolvimento , Animais , Bovinos , Contagem de Colônia Microbiana , Feminino , Microbiologia de Alimentos , Armazenamento de Alimentos , Doenças Transmitidas por Alimentos/microbiologia , Doenças Transmitidas por Alimentos/prevenção & controle , Leite/microbiologia , Temperatura , Vácuo
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...