Glyceric Acid Research Articles

Метаболомный профиль сыворотки крови у пациентов с язвенным колитом: патофизиологическая роль, диагностическое и терапевтическое значение

The incidence of inflammatory bowel disease (IBD) in both children and adults is increasing worldwide. While Crohn’s disease predominates in the pediatric population, ulcerative colitis (UC) more often affects the elderly. The relevance of metabolomic profiling in IBD has been confirmed in several studies revealing changes in endogenous and microbial metabolism associated with their pathogenesis. The metabolome composition of body fluids depends significantly on sex since sexual dimorphism is a trigger for metabolic differences between organisms. We have previously studied serum metabolic profiles in male patients with UC and identified candidate biomarkers of the disease. Objective. To determine the features of metabolome composition and candidate metabolite biomarkers of UC in women using a non-targeted serum metabolomic analysis. Patients and methods. This study included 10 women with active UC (moderately severe and severe attacks; a study group) aged 23 to 61 years (mean age: 35.2 ± 13.5 years) and 10 age-matched healthy volunteers (a control group) without IBD. Serum metabolites were analyzed by gas chromatography-mass spectrometry. Sample classification and search for potential biomarkers were performed using a partial least squares-discriminant analysis (PLS-DA), support vector machines (SVM), and a naïve Bayes classifier. ROC curves and areas under correlated curves were used to compare the success of different methods. Results. In serum samples from patients with UC and healthy volunteers, up to 90 low molecular weight compounds with different mass spectra and retention times were identified. The analysis revealed 25 compounds whose concentrations in the blood differed significantly between the study group and the comparison group (p <0.05). Six of the 25 compounds (adipic acid, β-glycerophosphate, glyceric acid, 2-hydroxybutyric acid, squalene, 2-palmitoylglycerol) were among the most significant 15 compounds detected by two classifiers at once (PLS-DA and SVM). Of these 15 compounds, only 7 were identical to the compounds that significantly altered in men: 2-hydroxybutyric acid, creatinine, β-glycerophosphate, α-glycerophosphate, trans-palmitoleic acid, palmitic acid, and squalene. Some of these compounds, just as in men, were associated with lipid metabolism disorders and glycolysis regulation (α-glycerophosphate), as well as with impaired osteogenesis (β-glycerophosphate). Conclusion. Significant differences were found between serum metabolomic profiles in women with UC and healthy volunteers. About half of the most significant compounds detected in the study group were identical to the compounds that were significantly altered in men with UC. In future investigations, the results obtained by non-targeted metabolomics, as well as the exact mechanisms of metabolic changes in UC patients, should be confirmed and clarified using targeted metabolomics and other omics. Key words: inflammatory bowel disease, ulcerative colitis, metabolome, biomarkers, gas chromatography-mass spectrometry

Metabolomic Alterations in Mammary Glands from Pubertal Mice Fed a High-Fat Diet.

Dietary malpractice is a risk factor for obesity. This study tested the hypothesis that consumption of a high-fat diet alters mammary metabolome in pubertal mice. We performed untargeted metabolomic analysis of primary metabolism on mammary glands from pubertal mice fed the AIN93G standard diet or a high-fat diet (HFD) for 3 weeks. We identified 97 metabolites for statistical comparisons. The HFD altered the amino acid metabolism considerably. This included elevated expression of branched-chain amino acids, non-essential amino acids (aspartic acid and glutamic acid), and methionine sulfoxide (oxidized methionine) and an alteration in the aminoacyl-tRNA biosynthesis pathway. Furthermore, elevations of fumaric acid and malic acid (both are citrate cycle intermediates) and glyceric acid (its phosphate derivatives are intermediates of glycolysis) in HFD-fed mice suggest an acceleration of both citrate cycle and glycolysis. Lower expression of glycerol, oleic acid, and palmitoleic acid, as well as decreased mammary expression of genes encoding lipid metabolism (Acaca, Fads1, Fasn, Scd1, and Srebf1) in HFD-fed mice indicate an attenuated lipid metabolism in the presence of adequate dietary fat. In conclusion, consumption of the HFD for 3 weeks alters metabolic profile of pubertal mammary glands. This alteration may affect mammary development and growth in pubertal mice.

Multi-omics reveals specific host metabolism-microbiome associations in intracerebral hemorrhage.

Intracerebral hemorrhage (ICH) is the most devastating subtype of stroke, but effective prevention and treatment strategies are lacking. Recently, gut microbiome and its metabolitesis are considered to be an influencing factor of stroke. However, little is known about the effects of the gut microbiome on ICH and host metabolic activity. Therefore, we used 16S sequencing, macrogenomics sequencing and untargeted metabolomics to explore the differences in gut microbial-metabolome interactions between patients with intracerebral hemorrhage and healthy control populations. We found a significant decrease in the phylum of Firmicutes and a significant increase of Bacteroidetes in ICH patients. At the genus level, Streptococcus, Bifidobacterium, Akkermansia, and Lactobacillus were more abundant in ICH patients. Macrogenomic analysis revealed active glycosaminoglycan degradation, heme synthesis, galactose degradation, lipopolysaccharide core region synthesis, and beta-Lactam resistance in ICH patients. Serum untargeted metabolomic analysis combined with ROC curves showed that octanoylcarnitine, decanoylcarnitine, dodecanoylcarnitine, glyceric acid, pyruvic acid, aspartic acid, methylcysteine, pyroglutamic acid, 9E-tetradecenoic acid, N-Acetylneuraminic acid, and aconitic acid were the best markers for the diagnosis of ICH. Correlation analysis showed that microbiome enriched in the gut of ICH patients were significantly correlated with serum metabolites, revealing a close correlation between the gut microbiome of ICH patients and the host metabolome, and significant differences from the healthy population. microbiota-host co-metabolites including pyruvic acid and 9E-tetradecenoic acid is associated with the the National Institutes of Health Stroke Scale (NIHSS) scores. In conclusion, microbiome-related metabolites in ICH patients was associated with the severity of ICH, the microbiota-host co-metabolites may be a potential may be potential therapeutic targets.

Carbon-based metal-free catalysts for selective oxidation of glycerol to glycolic acid

Exploring efficient and cheap catalyst for the selective oxidation of glycerol to valuable carboxylic acids is a critical and complicated challenge. Herein, we innovatively realized the efficient oxidation of glycerol to glycolic acid over metal-free catalyst under mild conditions via carbon material defect engineering. Multiple characterizations revealed that the stepwise functionalization of active carbon caused by simple high temperature control is adopted to fine-tune the composition and electronic structure of oxygen-containing functional groups. Specifically, the abundant ester and carboxyl functional groups exhibit stronger electronegativity than the hydroxyl group, and this enhanced electronic coupling effect strengthens the adsorption of glycerol, thus improving the catalytic activity. Kinetic analysis and density functional theory calculations demonstrated that the oxygen-containing functional groups (mainly ester and carboxyl) could promote the C–H bond activation of RCH2O* intermediate and once C–C bond cleavage of glyceric acid, ensuring the high selectivity of glycolic acid (53.2% over AC-400 catalyst). We anticipate that this work could sheds some light on the application and design of more new type of carbon-based metal-free catalysts in the aqueous phase oxidation of various polyols.

Catalytic Oxidation of Glycerol over Pt Supported on MOF-Derived Carbon Nanosheets.

A series of nitrogen-doped porous carbon nanosheets (NPCNs) doped with transition-metal-supported Pt catalysts were prepared by colloidal deposition and evaluated for the selective oxidation of glycerol to glyceric acid (GLYA) under nonalkaline conditions. The transition metal contained in the catalyst was found to affect its performance and selectivity for GLYA, with the Pt/Zr@NPCN catalyst showing the highest catalytic activity and selectivity. These materials were characterized using Brunauer-Emmett-Teller surface area analysis, transmission electron microscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and CO2 temperature-programmed desorption. The results showed that the small size of the Pt nanoparticles, the interaction between the Pt nanoparticles and the support, and the unique textural properties of the catalyst all promoted glycerol conversion and GLYA selectivity. A Zr concentration of 1.5 wt % and a support preparation temperature of 800 °C were found to provide a catalyst with the optimal performance that exhibited a glycerol conversion and selectivity for GLYA of 68.62 and 77.29%, respectively, at an initial O2 pressure of 10 bar and 60 °C after 6 h. Even after being recycled five times, this material provided a GLYA selectivity of approximately 75%, although the glycerol conversion decreased from 68 to 50%. The insights may provide new suggestions on the design of efficient support for the selective oxidation of polyols.

Enzymatic route for selective glycerol oxidation using covalently immobilized laccases

Glycerol is an important starting material for the synthesis of many chemical compounds and its selective oxidation represents an efficient way to produce value-added compounds. Glyceric acid, one of these selective oxidation products, is an important intermediate in the food, medicine, cosmetics, and light industries. In this work, four commercially available native laccases were screened for glycerol oxidation using different initiators, and the two most efficient biocatalysts were covalently immobilized on functionalized magnetic and polymethacrylate (Lifetech™) solid supports. Apart from the mostly employed Fe3O4 magnetic particles, in this work Ni-Zn or Ni-Zn-Co spinel ferrite (MFe2O4) microparticles were used. Particularly, the utilization (for the first time for laccase immobilization) of Ni-Zn ferrite support Ni0.7Zn0.3Fe2O4 functionalized with 3-aminopropyl-trimethoxysilane, via crosslinking by glutaraldehyde and reduction with NaBH4 led to excellent biocatalytic efficiency and stability. These results confirm the feasibility of Trametes versicolor laccase for covalent bonding, as presumed by computational modelling. The resulted enzymatic preparations were characterized in detail in terms of stability and reusability, demonstrating enhanced storage, pH and thermal stability compared to the native enzymes. The most active biocatalysts (790.93 [U/g]) were successfully used for glycerol oxidation and the specific conversion in glyceric acid exceeded 50%.

Heme Oxygenase-1 and Blood Bilirubin Are Gradually Activated by Oral D-Glyceric Acid.

It has been shown that small doses of oral D-glyceric acid (DGA) activate mitochondrial metabolism and reduce inflammation among 50-60-year-old healthy volunteers. The present results with the same small doses reveal that after a 4-day DGA regimen, a dose of DGA activated the HO-1 pathway acutely, while enhanced inflammatory status after the 4-day DGA regimen seemed to be able to downregulate the HO-1 pathway in non-acute measurement. Blood bilirubin was strongly upregulated towards the end of the altogether 21-day study period with positive associations towards improved inflammation and reduced blood triglycerides. After the 4-day DGA regimen, hepatic inflow of blood bilirubin with albumin as the carrier was clearly upregulated in the lower-aerobic-capacity persons. At the same time also, blood triglycerides were down, pointing possibly to the activation of liver fatty acid oxidation. The combination of activated aerobic energy metabolism with transient HO-1 pathway activation and the upregulation of blood bilirubin may reduce the risks of chronic diseases, especially in aging. Furthermore, there exist certain diseases with unsatisfactorily-met medical needs, such as fatty and cholestatic liver diseases, and Parkinson's disease, that can be possibly ameliorated with the whole-body mechanism of the action of the DGA regimen.

Carbon paper supported gold nanoflowers for tunable glycerol electrooxidation boosting efficient hydrogen evolution

Thermodynamically favorable selective electrooxidation reactions coupled with hydrogen evolution reaction (HER) is a promising strategy for simultaneous production of value-added chemicals and hydrogen. In this work, a binder-free gold nanoflowers electrode based on carbon paper is prepared and used as anode catalyst, which results in good charge transfer, high stability and superior catalytic activity for electrooxidation of glycerol. We develop an integrated system of glycerol electrooxidation with HER, and the effect of potential on the distribution of anodic electrooxidation products and cathodic hydrogen production are investigated. At 1.0 V, the overall reaction reaches 10 mA cm−2 and the selectivity of glyceric acid (GLA) reaches 97.2%. At 1.2 V, hydrogen production reaches the highest value of 960 μmol L−1 and the anode product consists of a mixture of glyceric acid, glycolic acid (GA) and formic acid (FA). At 1.3 V, the selectivity of FA reaches 87.3%. Operando technique in situ infrared spectroscopy is used to monitor the immediate evolution and study the pathway of controlled glycerol electrooxidation. This work demonstrates carbon paper is a promising substrate material of binder-free electrode applied in thermodynamically favorable electrocatalytic reactions boosting hydrogen evolution.

Cordycepin exhibits anti-fatigue effect via activating TIGAR/SIRT1/PGC-1α signaling pathway

Fatigue, a most commonly sub-health condition, may cause people more susceptible to many diseases. Cordycepin, a principal active ingredient from Cordyceps militaris, exerts various pharmacological activities including anti-diabetes, anti-inflammatory, immunomodulatory and antioxidant effects. However, the anti-fatigue effect of cordycepin and specific mechanism remained unclear. This study aimed to investigate the beneficial effect of cordycepin on physical fatigue and elucidate the potential mechanism. 20 mg/kg, 40 mg/kg of cordycepin and 500 mg/kg taurine were respectively treated to mice for 28 days before weight-loaded swimming test. The results revealed that cordycepin significantly prolonged the weight-loaded swimming time of mice. Meanwhile, cordycepin decreased the levels of lactic acid, blood uric nitrogen, and malondialdehyde, and increased the contents of superoxide dismutase, glutathione, nicotinamide adenine dinucleotide phosphate, hepatic glycogen, muscle glycogen and ATP. The metabolomic study by GC-MS showed that eight biomarkers were found in livers, including L-lactic acid, L-asparagine, 3-phosphoglyceric acid, inosine, D-galactose, L-tyrosine, glyceric acid and L-threonine. There were seven biomarkers in gastrocnemius, including D-ribose-5-phosphate, acetic acid, propionic acid, butyric acid, palmitic acid, oxaloacetic acid and citric acid. The results of metabolomics indicated that cordycepin might relieve fatigue by regulating energy metabolism and pentose phosphate pathway. Furthermore, we found cordycepin significantly enhanced the protein levels of TIGAR, SIRT1, PGC-1α, NRF1 and TFAM in gastrocnemius of weight-loaded swimming mice. Taken together, the present study demonstrated that cordycepin possessed an anti-fatigue effect via activating TIGAR/SIRT1/PGC-1α signaling pathway. Our study indicated that cordycepin may be a potentially efficient candidate for fatigue.

Low-Temperature Production of Glyceric Acid from Biomass-Based Sugar via the Cooperative Roles of MgO and NaBF4

Low-Temperature Production of Glyceric Acid from Biomass-Based Sugar via the Cooperative Roles of MgO and NaBF₄

Metabolic profiling and biochemical analysis of stored Hass avocado fruit by GC‐MS and UHPLC‐UV‐VIS revealed oxidative stress as the main driver of ‘blackspot’ physiological disorder

SummaryThe goal of this study was to use GC‐MS and UHPLC‐UV‐VIS‐based metabolomic tools combined with chemometric analysis to discriminate between fruit with blackspot physiological disorder independently of storage condition (regular air or controlled atmosphere) and without blackspot (hereafter referred to as ‘Control’). The study looked at polar metabolites, enzymes, fatty acids and oxidative stress markers. Fruit with high levels of lenticel damage are more likely to develop blackspot, which appears to be exacerbated by H2O2 and peroxidation of lipids. Lower catalase (CAT), peroxidase (POD), polyphenol oxidase (PPO), superoxide dismutase (SOD) and phenylalanine‐ammonia lyase (PAL) activities together with lower levels of polyphenols (syringic acid, epigallocatechin, quercetin and vanillic) and fatty acids (linolenic, linoleic and palmitic acid), as well as ß‐sitosterol, methyl‐3‐hydroxybutyrate, glyceric acid, hydroxyl butanoic acid, L‐threonic acid, hydroxyl glutaric acid and xylose contributed to a higher prevalence of blackspot disorder in stored Hass avocados, which was accompanied by upregulation of soluble proteins. Finally, chemometric analysis revealed a positive relationship between blackspot disorder with gluconic, palmitoleic, galactose oxime, glyceric, hydroxyglutaric, MDA, syringic and oleic acid, as well as a negative relationship with catechin, epigallocatechin, SOD, CAT and tagatose. The study concluded that oxidative stress is the main driver of ‘Blackspot’ physiological disorder.

Pd supported on defective TiO2 polymorphic mixtures: Effect of metal-support interactions upon glycerol selective oxidation

Palladium catalysts supported on defective mixes of anatase, TiO2 (II) and rutile crystalline phases, previously obtained by high-energy ball milling, were synthesized and tested for glycerol selective oxidation. A deep characterization of these unusual materials was carried out to elucidate catalytic and physicochemical features. Electron density transfer from support to metal or vice versa, depending on the polymorphs present, could not only alter palladium particle sizes and its surface oxidation state but also reducibility and oxygen mobility of catalysts. Furthermore, acid-base properties achieved also influenced catalytic activity under mild conditions of liquid-phase glycerol oxidation. A conversion of 94% and a selectivity to glyceric and lactic acids of 48% and 22% respectively were obtained for the Pd catalyst supported on mechanochemically activated anatase. The presence of several polymorphs in a metal oxide support could therefore benefit or handicap catalytic cycle for a particular reaction. Metal-support interactions play a key role in heterogenous catalysts and thus the rational design of supports comes on the scene.

Influence of sacrificial agent on Cu photodeposition over TiO2/MCH composites for photocatalytic hydrogen production

Titanium (ca. 11 wt%) was dispersed on a carbonaceous mesoporous support and modified with copper (ca. 5 wt%) photodeposited using either glycerol or methanol as the sacrificial agent ((Cu-TiO2/MCH_(Gly) and Cu-TiO2/MCH_(Met) solids, respectively). In the former case, copper particles were more preferentially deposited on titania and copper nanoaggregates were more abundant than in the latter. The synthesized catalysts were tested in the glycerol photoreforming reaction and it was found that there was an increase in activity on copper photodeposition as compared to titania-mesoporous carbon composite, being higher in Cu-TiO2/MCH_(Gly) than in Cu-TiO2/MCH_(Met) (5 and 4 times, respectively). Nevertheless, copper present in Cu-TiO2/MCH_(Gly) redisperses as reaction proceeds, the catalyst exhibiting a more similar activity to Cu-TiO2/MCH_(Met) after one use. An additional reason for catalyst deactivation is strong adsorption of reaction intermediates. In this sense, competitive reactions with glycolic and glyceric acid (two of the intermediates identified by HPLC-DAD/RID) and glycerol gave some hints on reaction mechanism which could also be helpful for future identification of the species responsible for the catalysts deactivation.

Identification of Exhaled Metabolites in Children with Cystic Fibrosis.

The early detection of inflammation and infection is important to prevent irreversible lung damage in cystic fibrosis. Novel and non-invasive monitoring tools would be of high benefit for the quality of life of patients. Our group previously detected over 100 exhaled mass-to-charge (m/z) features, using on-line secondary electrospray ionization high-resolution mass spectrometry (SESI-HRMS), which distinguish children with cystic fibrosis from healthy controls. The aim of this study was to annotate as many m/z features as possible with putative chemical structures. Compound identification was performed by applying a rigorous workflow, which included the analysis of on-line MS2 spectra and a literature comparison. A total of 49 discriminatory exhaled compounds were putatively identified. A group of compounds including glycolic acid, glyceric acid and xanthine were elevated in the cystic fibrosis group. A large group of acylcarnitines and aldehydes were found to be decreased in cystic fibrosis. The proposed compound identification workflow was used to identify signatures of volatile organic compounds that discriminate children with cystic fibrosis from healthy controls, which is the first step for future non-invasive and personalized applications.

Electrocatalytic selective oxidation of glycerol to glyceric acid over efficient Pt/CNTs-CeO2 catalysts

• Novel Pt/CNTs-CeO 2 was developed for glycerol electrooxidation. • CeO 2 provided strong electronic interaction with Pt nanoparticles. • Pt/CNTs-CeO 2 delivered superior anti-poisoning capability. • High glycerol conversion and glyceric acid selectivity was obtained around mild reaction condition. Pt/CNTs-CeO 2 electrocatalysts are prepared by the electrodeposition method and used for the selective oxidation of glycerol to produce glyceric acid (GLYA). By introducing CeO 2 to Pt/CNTs catalyst, the electronic structure of Pt is modulated and anti-poisoning ability is improved, which leads to the high electrocatalytic performance and stability of Pt/CNTs-CeO 2 catalyst. The conversion of glycerol on the Pt/CNTs-CeO 2 electrode reaches 55.3 % after applying 0.8 V versus a reversible hydrogen electrode for 4 h, and the GLYA selectivity can achieve 58.8% under such mild reaction conditions..

The support influence of Au‐based catalysts in glycerin selective oxidation to glyceric acid

AbstractBackgroundThe sustainable conversion of biomass‐derived glycerin into high‐value‐added chemicals is a significant challenge in contemporary science. In this context, the selective oxidation of aqueous glycerin into glyceric acid was investigated in the presence of NaOH and atmospheric oxygen. It was demonstrated that the selective transformation of glycerin to glyceric acid involves a new chemical reaction path for commodity glyceric acid that is both abundant and economical.ResultsThe hydrotalcite‐supported Au nanoparticle catalyst (5%Au/HT) was found to be the most active for glycerin selective transformation to glyceric acid, showing 89.5% glycerin conversion with 61.2% glyceric acid selectivity under optimum experimental conditions. Furthermore, the 5%Au/HT catalyst was reused six times and maintained nearly the same activity in the catalytic recycle experiments.ConclusionIn the Au‐based catalysts, there are strong electronic interactions between the different supports and Au nanoparticles (Au NPs). Besides, the basic sites of the catalysts participated in promotion of hydroxyl functional groups. © 2022 Society of Chemical Industry (SCI).

Liquid chromatography coupled to high-resolution mass spectrometry metabolomics: A useful tool for investigating tumor secretome based on a three-dimensional co-culture model.

Three-dimensional (3D) cell culture technologies, which more closely mimic the complex microenvironment of tissue, are being increasingly evaluated as a tool for the preclinical screening of clinically promising new molecules, and studying of tissue metabolism. Studies of metabolites released into the extracellular space (secretome) allow understanding the metabolic dynamics of tissues and changes caused by therapeutic interventions. Although quite advanced in the field of proteomics, studies on the secretome of low molecular weight metabolites (< 1500 Da) are still very scarce. We present an untargeted metabolomic protocol based on the hybrid technique of liquid chromatography coupled with high-resolution mass spectrometry for the analysis of low-molecular-weight metabolites released into the culture medium by 3D cultures and co-culture (secretome model). For that we analyzed HT-29 human colon carcinoma cells and 3T3-L1 preadipocytes in 3D-monoculture and 3D-co-culture. The putative identification of the metabolites indicated a sort of metabolites, among them arachidonic acid, glyceric acid, docosapentaenoic acid and beta-Alanine which are related to cancer and obesity. This protocol represents a possibility to list metabolites released in the extracellular environment in a comprehensive and untargeted manner, opening the way for the generation of metabolic hypotheses that will certainly contribute to the understanding of tissue metabolism, tissue-tissue interactions, and metabolic responses to the most varied interventions. Moreover, it brings the potential to determine novel pathways and accurately identify biomarkers in cancer and other diseases. The metabolites indicated in our study have a close relationship with the tumor microenvironment in accordance with the literature review.

Pt1 enhanced C-H activation synergistic with Ptn catalysis for glycerol cascade oxidation to glyceric acid

The selective oxidation of glycerol to glyceric acid, an important value-added reaction from polyols, is a typical cascade catalytic process. It is still of great challenge to simultaneously achieve high glycerol activity and glyceric acid selectivity, suffering from either deep oxidation and C-C cleavage or poor oxidation efficiency from glyceraldehyde to glyceric acid. Herein, this work, inspired by nature, proposes a cascade synergistic catalysis strategy by atomic and low-coordinated cluster Pt on well-defined Cu-CuZrOx, which involves enhanced C-H activation on atomic Pt1 and O-H activation on cluster Ptn in the oxidation of glycerol to glyceraldehyde, and cluster Ptn for C=O activation followed by O-H insertion and atomic Pt1 for C-H activation in the tandem oxidation of glyceraldehyde to glyceric acid. The enhanced C-H activation in the cascade process by atomic Pt1 is revealed to be essential for the high glycerol activity (90.0±0.1%) and the glyceric acid selectivity (80.2±0.2%).

Gut Microbial Composition and Liver Metabolite Changes Induced by Ammonia Stress in Juveniles of an Invasive Freshwater Turtle.

Simple SummaryThe ammonia content in aquaculture waterbodies can easily achieve a relatively high level, largely due to the excretion of intensively farmed aquatic animals and the decomposition of residual food particles. Excess ammonia may exert prominent toxicities to all aquatic species. Many freshwater turtles have become economically important aquaculture species in some countries. The evaluation of the toxic effects of ammonia on these cultured turtle species is rarely considered, despite having been extensively conducted in many invertebrates and fish. Various omics techniques can be applied to comprehensively analyze diverse biological responses at different levels in pollutant-exposed individuals. In order to increase our understanding of the physiological changes under ammonia stress in cultured turtle species, we exposed juveniles of the red-eared slider turtle (Trachemys scripta elegans) to different concentrations (0, 0.3, 3.0, and 20.0 mg/L) of ammonium chloride solution for 30 days, and then measured their swimming performance, growth rate, gut microbial composition, and liver metabolic profiling. No significant change in swimming ability was found in ammonia-exposed turtles, but a relatively low growth rate was exhibited in the 20.0 mg/L ammonia-exposed turtles. Although no significant differences in the alpha and beta diversity measures of the gut microbial community were observed, the microbial composition seemed to be different among different treatment groups. Some pathogenic bacteria were found to increase in ammonia-exposed turtles. Liver metabolic profiling based on liquid chromatography–mass spectrometry showed that a series of metabolites (such as leucine, valine, arginine, glutamine, adenosine diphosphate, glyceric acid, myo-inositol, gamma-aminobutyric acid, etc.) were significantly altered in ammonia-exposed turtles. Accordingly, ammonia exposure might alter the health status of guts due to increased pathogenic bacteria, and disturb multiple metabolic pathways (such as amino acid, nucleotide, lipid metabolism, energy metabolism, etc.) in juveniles of T. scripta elegans.As the most common pollutant in aquaculture systems, the toxic effects of ammonia have been extensively explored in cultured fish, molluscs, and crustaceans, but have rarely been considered in turtle species. In this study, juveniles of the invasive turtle, Trachemys scripta elegans, were exposed to different ammonia levels (0, 0.3, 3.0, and 20.0 mg/L) for 30 days to evaluate the physiological, gut microbiomic, and liver metabolomic responses to ammonia in this turtle species. Except for a relatively low growth rate of turtles exposed to the highest concentration, ammonia exposure had no significant impact on the locomotor ability and gut microbial diversity of turtles. However, the composition of the microbial community could be altered, with some pathogenic bacteria being increased in ammonia-exposed turtles, which might indicate the change in their health status. Furthermore, hepatic metabolite profiles via liquid chromatography–mass spectrometry revealed extensive metabolic perturbations, despite being primarily involved in amino acid biosynthesis and metabolism. Overall, our results show that ammonia exposure causes gut dysbacteriosis and disturbs various metabolic pathways in aquatic turtle species. Considering discrepant defense mechanisms, the toxic impacts of ammonia at environmentally relevant concentrations on physiological performance might be less pronounced in turtles compared with fish and other invertebrates.

Rational screening of metal catalysts for selective oxidation of glycerol to glyceric acid from microkinetic analysis

AbstractRational screening of efficient supported metal catalysts is still a great challenge due to the complicated reaction mechanism for selective polyol oxidation. Exemplifying glycerol oxidation to glyceric acid as a model reaction, we perform a DFT assisted descriptor based microkinetic modeling to reveal the underlying mechanism. It is found that the addition/formation of OH− could polarize the metal surface (M‐OH*) to regulate the d‐band center of Pt accompanied by the electron transfer from OH− to metal atoms, thus promoting the adsorption of glycerol. Moreover, the linear chemisorption energy and transition state energy scaling relations are well established on the formation energies of adsorbed C and O. Activity map obtained from descriptor based microkinetic analysis demonstrates that Pt and Ir metals exhibit the highest catalytic activity. Meanwhile, further analysis of the desorption energy and CC bond cleavage activation energy of glyceric acid product shows that Au and Pt metals display the optimal glyceric acid selectivity. Satisfactorily, these results from microkinetic analysis are in good agreement with the comparative experimental results. The insights revealed here may open a new avenue for rational design of transition metal catalysts in the bio‐polyol oxidation system.