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•Experimental and in-silico study on HDO of biobased 5-hydroxymethylfurfural.•Deoxygenation at higher temperatures relative to reduction of the aldehyde.•Despite reducibility ...improvements, La promotion slowed reaction rates and activity.•Nb promotion facilitated deoxygenation rates and humin formation.•Directly comparable kinetic parameters and TOF for carbon-supported Ni catalysts.
Catalytic hydrodeoxygenation of hydroxymethylfurfural was investigated in a three-phase batch reactor over a range of reaction temperatures (170–230 °C), under 5 MPa of hydrogen, and tetrahydrofuran solvent. Nickel-based carbon-supported catalysts were also promoted by lanthanum and niobium, despite promoters alone demonstrated no activity. Based on experimentally-obtained liquid products, a reaction pathway was proposed and a microkinetic model was established, by considering adsorption, desorption and surface reaction kinetics, mass transfer and thermodynamics. An unpromoted Ni/C resulted in primarily unsaturated furan diol, a highly desirable intermediate in the polymer industry. As reaction temperatures increased > 200 °C, dehydration yielded deoxygenated products suitable for solvents and biofuel. In spite of enhancements to reducibility, La-promotion significantly decreased both hydrogenation (8-times) and deoxygenation (25-times) rate constants. Alternatively, Nb-incorporation offered additional acidity, while lower activation energies resulted in 200% higher deoxygenation rates via dehydration reactions and humin formation at lower temperatures. It exhibited the highest deoxygenation activity.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Background Irritable bowel syndrome (IBS) is a multifactorial disease for which a dysbiosis of the gut microbiota has been described. Bile acids (BA) could play a role as they are endogenous ...laxatives and are metabolized by gut microbiota. We compared fecal BA profiles and microbiota in healthy subjects (HS) and patients with diarrhea‐predominant IBS (IBS‐D), and we searched for an association with symptoms.
Methods Clinical features and stool samples were collected in IBS‐D patients and HS. Fecal BA profiles were generated using HPLC coupled to tandem mass spectrometry. The fecal microbiota composition was assessed by q‐PCR targeting dominant bacterial groups and species implicated in BA transformation.
Key Results Fourteen IBS‐D patients and 18 HS were included. The two groups were comparable in terms of age and sex. The percentage of fecal primary BA was significantly higher in IBS‐D patients than in HS, and it was significantly correlated with stool consistency and frequency. Fecal counts of all bacteria, lactobacillus, coccoides, leptum and Faecalibacterium prausnitzii were similar. There was a significant increase of Escherichia coli and a significant decrease of leptum and bifidobacterium in IBS‐D patients.
Conclusions & Inferences We report an increase of primary BA in the feces of IBS‐D patients compared to HS, correlated with stool consistency and frequency. A dysbiosis of different bacterial groups was detected, some of them involved in BA transformation. As the gut microbiota is the exclusive pathway to transform primary into secondary BA, this suggests a functional consequence of dysbiosis, leading to lower BA transformation.
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BFBNIB, DOBA, FZAB, GIS, IJS, IZUM, KILJ, NLZOH, NUK, OILJ, PILJ, PNG, SAZU, SBCE, SBMB, SIK, UILJ, UKNU, UL, UM, UPUK
Aims
The role of a Acinetobacter johnsonii strain, isolated from a soil sample, in the biotransformation of bile acids (BAs) was already described but the enzymes responsible for these ...transformations were only partially purified and molecularly characterized.
Methods and Results
This study describes the use of hybrid de novo assemblies, that combine long‐read Oxford Nanopore and short‐read Illumina sequencing strategies, to reconstruct the entire genome of A. johnsonii ICE_NC strain and to identify the coding region for a 12α‐hydroxysteroid dehydrogenase (12α‐HSDH), involved in BAs metabolism. The de novo assembly of the A. johnsonii ICE_NC genome was generated using Canu and Unicycler, both strategies yielded a circular chromosome of about 3.6 Mb and one 117 kb long plasmid. Gene annotation was performed on the final assemblies and the gene for 12α‐HSDH was detected on the plasmid.
Conclusions
Our findings illustrate the added value of long read sequencing in addressing the challenges of whole genome characterization and plasmid reconstruction in bacteria. These approaches also allowed the identification of the A. johnsonii ICE_NC gene for the 12α‐HSDH enzyme, whose activity was confirmed at the biochemical level.
Significance and impact or the study
At present, this is the first report on the characterization of a 12α‐HSDH gene in an A. johnsonii strain able to biotransform cholic acid into ursodeoxycholic acid, a promising therapeutic agent for several diseases.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
5.
Bile acids and the gut microbiome Ridlon, Jason M; Kang, Dae J; Hylemon, Phillip B ...
Current opinion in gastroenterology
30, Issue:
3
Journal Article
Peer reviewed
Open access
PURPOSE OF REVIEWWe examine the latest research on the emerging bile acid-gut microbiome axis and its role in health and disease. Our focus revolves around two key microbial pathways for degrading ...bile salts, and the impact of bile acid composition in the gut on the gut microbiome and host physiology.
RECENT FINDINGSBile acid pool size has recently been shown to be a function of microbial metabolism of bile acids in the intestines. Recent studies have shown potential mechanisms explaining how perturbations in the microbiome affect bile acid pool size and composition. Bile acids are emerging as regulators of the gut microbiome at the highest taxonomic levels. The role of bile acids as hormones and potentiators of liver cancer is also emerging.
SUMMARYThe host and microbiome appear to regulate bile acid pool size. The host produces a large, conjugated hydrophilic bile acid pool, maintained through positive-feedback antagonism of farnesoid X receptor (FXR) in intestine and liver. Members of the microbiome utilize bile acids and their conjugates resulting in agonism of FXR in intestine and liver resulting in a smaller, unconjugated hydrophobic bile acid pool. Hydrophilicity of the bile acid pool is associated with disease states. Reduced bile acid levels in the gut are associated with bacterial overgrowth and inflammation. Diet, antibiotic therapy, and disease states affect the balance of the microbiome-bile acid pool.
Emerging evidence strongly suggest that the human "microbiome" plays an important role in both health and disease. Bile acids function both as detergents molecules promoting nutrient absorption in ...the intestines and as hormones regulating nutrient metabolism. Bile acids regulate metabolism via activation of specific nuclear receptors (NR) and G-protein coupled receptors (GPCRs). The circulating bile acid pool composition consists of primary bile acids produced from cholesterol in the liver, and secondary bile acids formed by specific gut bacteria. The various biotransformation of bile acids carried out by gut bacteria appear to regulate the structure of the gut microbiome and host physiology. Increased levels of secondary bile acids are associated with specific diseases of the GI system. Elucidating methods to control the gut microbiome and bile acid pool composition in humans may lead to a reduction in some of the major diseases of the liver, gall bladder and colon.
Concomitant selective dehydroxylation during the transformation of flavones into pyrazoles with hydrazine is determined by the A‐ring substitution pattern and propensity to keto enol tautomerization. ...The obtained pyrazoles show varied tyrosinase inhibition properties, including one nanomolar inhibitor.
Concomitant selective dehydroxylation during the transformation of flavones into pyrazoles with hydrazine is determined by the A‐ring substitution pattern and propensity to keto–enol tautomerization. The obtained pyrazoles show varied tyrosinase inhibition properties, including one nanomolar inhibitor.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SBCE, SBMB, UL, UM, UPUK
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•Activation of C−O bonds was promoted by the interfacial sites of Ni and TiO2.•Modified by TiO2−x, Ni/SBA-15 catalytic performance has been increased 4 times.•TiO2 promoted the ...dispersion of Ni particles and the reduction of Ni2+ to Ni0.•Catalytic activities were related to the ratios of Ni0 to Ti3+.
The presence of oxygenated compounds in coal-based crude oil seriously affects its calorific value. Dibenzofuran, as a compound with a certain content in coal-based crude oil and difficult to hydrodeoxygenate, is often chosen as a model compound. The influence of decorating the surface of a Ni catalyst with TiO2 on the activity and selectivity for dibenzofuran hydrodeoxygenation was investigated in this study. Ring opening and dehydroxylation of six oxygen-containing intermediates on the Ni(111) surface and the interfacial sites between Ni(111) and TiO2 were compared by density functional theory calculations. Results showed that the activation of C−O bonds was promoted by the enhanced adsorption of oxygen-containing intermediates at the interfacial sites. The decoration of TiO2 on Ni metal can obviously promote the conversion of dibenzofuran and selectivity of deoxygenation products. The yield of the target product of bicyclohexane was the highest and reached up to 94.8% when the mole ratio of Ni/Ti was 1:3. The addition of TiO2 not only promoted the dispersion of Ni particles but also enhanced the reduction of Ni2+ to Ni0. However, there were no significant electronic modifications were detected for the bulk of the metallic Ni particles and changed the acidity of the catalyst. It is concluded that the improved deoxygenation performance of the catalyst was due to the interfacial sites created by TiO2 decorating on the surface of Ni particles. It can provide a valuable reference for catalysts design of fuel conversion technology and environmental science.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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•Dry synthesis method for utilizing active sites of cobalt oxides on alumina.•Combined alumina dehydroxylation and solid-state impregnation for dry synthesis.•Active control of ...hydroxyl groups and Al penta sites over γ-Al2O3 surface.•Enhanced redox property via selectively favored Co3O4 phase formation.•Designing catalyst where strong support-metal interaction has negative effects.
Alumina-supported cobalt oxide excels as an oxidation catalyst, however, strong metal-support interactions (SMSI) of cobalt and alumina can lead to inactive phases such as cobalt aluminate. To avoid the formation of the inactive phase, it was hypothesized that reducing the number of hydroxyl group anchoring sites on the alumina would enable a higher ratio of active cobalt oxide than inactive phases. We devised a dry synthesis method combined with alumina dehydroxylation and solid-state impregnation of cobalt. Characterization results including XRD, XPS, and Raman spectroscopy confirm the formation of the desired active phase on the dehydroxylated alumina. The resultant catalysts demonstrate a surprising decrease in the cobalt content (max. tenfold from 20 wt.% to 2 wt.% of cobalt loading) for oxidations of NH3 and CO, respectively, suggesting practically useful synthesis method for highly active supported catalysts.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Background & Aims The 7α-dehydroxylation of primary bile acids (BAs), chenodeoxycholic (CDCA) and cholic acid (CA) into the secondary BAs, lithocholic (LCA) and deoxycholic acid (DCA), is a key ...function of the gut microbiota. We aimed at studying the linkage between fecal BAs and gut microbiota in cirrhosis since this could help understand cirrhosis progression. Methods Fecal microbiota were analyzed by culture-independent multitagged-pyrosequencing, fecal BAs using HPLC and serum BAs using LC–MS in controls, early (Child A) and advanced cirrhotics (Child B/C). A subgroup of early cirrhotics underwent BA and microbiota analysis before/after eight weeks of rifaximin. Results Cross-sectional: 47 cirrhotics (24 advanced) and 14 controls were included. In feces, advanced cirrhotics had the lowest total, secondary, secondary/primary BA ratios, and the highest primary BAs compared to early cirrhotics and controls. Secondary fecal BAs were detectable in all controls but in a significantly lower proportion of cirrhotics ( p <0.002). Serum primary BAs were higher in advanced cirrhotics compared to the rest. Cirrhotics, compared to controls, had a higher Enterobacteriaceae (potentially pathogenic) but lower Lachonospiraceae , Ruminococcaceae and Blautia (7α-dehydroxylating bacteria) abundance. CDCA was positively correlated with Enterobacteriaceae (r = 0.57, p <0.008) while Ruminococcaceae were positively correlated with DCA (r = 0.4, p <0.05). A positive correlation between Ruminococcaceae and DCA/CA (r = 0.82, p <0.012) and Blautia with LCA/CDCA (r = 0.61, p <0.03) was also seen. Prospective study: post-rifaximin, six early cirrhotics had reduction in Veillonellaceae and in secondary/primary BA ratios. Conclusions Cirrhosis, especially advanced disease, is associated with a decreased conversion of primary to secondary fecal BAs, which is linked to abundance of key gut microbiome taxa.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
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