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Glycerol-based biorefinery can be a highly profitable process by producing highly value-added products such as dihydroxyacetone via combined catalytic strategies. Here, two-enzyme system is adopted for the transformation of glycerol into highly valuable dihydroxyacetone as well as cofactor regeneration at the same time. Glycerol dehydrogenase (GDH) and alcohol dehydrogenase (ADH) are co-immobilized within magnetically separable and spherical mesocellular silica foam (Mag-S-MCF), to prepare NER-(GDH/ADH). In details, GDH and ADH are adsorbed into the mesopores of Mag-S-MCF, and further crosslinked within the mesopores of Mag-S-MCF. The resulting nanoscale enzyme reactors (NER) of crosslinked GDH and ADH molecules within the bottle-neck structured mesopores can effectively prevent larger sized crosslinked enzyme aggregates from being leached out of smaller mesopores, due to the bottle-neck mesopore structure of Mag-S-MCF, as well as stabilize the activity of GDH and ADH upon chemical crosslinking, effectively preventing the denaturation of enzyme molecules. More importantly, the proximity of GDH and ADH molecules within mesopores of NER improves the efficiency of cofactor-mediated dual-enzymatic reactions by relieving mass-transfer limitations and improving cofactor recycling in an effective way, expediting both glycerol oxidation and dihydroxyacetone generation at the same time. As a result, the DHA concentration of NER-(GDH/ADH) and the simple mixture of NER-GDH and NER-ADH were 410 μM and 336 μM, respectively. To the best of our knowledge, this report is the first demonstration of stabilized nanoscale multi-enzyme reactor system, equipped with efficient cofactor regeneration within confined mesopores, for efficient glycerol transformation to high-valued dihydroxyacetone. [ABSTRACT FROM AUTHOR]

Species of the genus Blautia are not only abundant in the human gut but also contribute to human well‐being. Our study demonstrates that the gut acetogen Blautia schinkii can grow on myo‐inositol. We identified the pathway of myo‐inositol degradation through a combination of physiological and biochemical studies, genome‐wide expression profiling and homology searches. Initially, myo‐inositol is oxidized to 2‐keto‐myo‐inositol. This compound is then metabolized by a series of enzymes – a dehydratase, hydrolase, isomerase and kinase – to form 2‐deoxy‐5‐keto‐d‐gluconic acid 6‐phosphate. This intermediate is split by an aldolase into malonate semialdehyde and dihydroxyacetone phosphate, which is an intermediate of the Embden–Meyerhof–Parnas pathway. This pathway leads to the production of pyruvate and, subsequently, acetate. Concurrently, malonate semialdehyde is reduced to 3‐hydroxypropionate (3‐HP). The genes responsible for myo‐inositol degradation are clustered on the genome, except for the gene encoding the aldolase. We identified the putative aldolase Fba_3 and 3‐HP dehydrogenase Adh1 encoding genes bioinformatically and verified them biochemically using enzyme assays with heterologously produced and purified protein. The major fermentation end products were 3‐HP and acetate, produced in similar amounts. The production of the unusual fermentation end product 3‐HP is significant not only for human health but also for the potential bioindustrial production of this highly desired compound. [ABSTRACT FROM AUTHOR]

Inhalation exposures to dihydroxyacetone (DHA) occur through spray tanning and e-cigarette aerosols. Several studies in skin models have demonstrated that millimolar doses of DHA are cytotoxic, yet the genotoxicity was unclear. We examined the genotoxicity of DHA in cell models relevant to inhalation exposures. Human bronchial epithelial cells BEAS-2B, lung carcinoma cells A549, cardiomyocyte Ac16, and hepatocellular carcinoma HepG3 were exposed to DHA, and low millimolar doses of DHA were cytotoxic. IC90 DHA doses induced cell cycle arrest in all cells except the Ac16. We examined DHA's genotoxicity using strand break markers, DNA adduct detection by Repair Assisted Damage Detection (RADD), metaphase spreads, and a forward mutation assay for mutagenesis. Similar to results for skin, DHA did not induce significant levels of strand breaks. However, RADD revealed DNA adducts were induced 24 h after DHA exposure, with BEAS-2B and Ac16 showing oxidative lesions and A549 and HepG3 showing crosslink-type lesions. Yet, only low levels of reactive oxygen species or advanced glycation end products were detected after DHA exposure. Metaphase spreads revealed significant increases in chromosomal aberrations in the BEAS-2B and HepG3 with corresponding changes in ploidy. Finally, we confirmed the mutagenesis observed using the supF reporter plasmid. DHA increased the mutation frequency, consistent with methylmethane sulfonate, a mutagen and clastogen. These data demonstrate DHA is a clastogen, inducing cell-specific genotoxicity and chromosomal instability. The specific genotoxicity measured in the BEAS-2B in this study suggests that inhalation exposures pose health risks to vapers, requiring further investigation. [ABSTRACT FROM AUTHOR]

The growing demand for sustainable chemical production has spurred significant interest in biocatalysis. This study is framed within the biocatalytic production of 1,3-dihydroxyacetone (DHA) from glycerol, a byproduct of biodiesel manufacturing. The main goal of this study is to address the challenge of identifying the optimal operating conditions. To achieve this, catalytic potential, a lumped parameter that considers both the activity and stability of immobilized biocatalysts, was used to guide the design of a multi-enzymatic system. The multi-enzymatic system comprises glycerol dehydrogenase (GlyDH) and NADH oxidase (NOX). The enzymatic oxidation of glycerol to DHA catalyzed by GlyDH requires the cofactor NAD+. The integration of NOX into a one-pot reactor allows for the in situ regeneration of NAD+, enhancing the overall efficiency of the process. Furthermore, immobilization on Ni+2 agarose chelated supports, combined with post-immobilization modifications (glutaraldehyde crosslinking for GlyDH), significantly improved the stability and activity of both enzymes. The catalytic potential enabled the identification of the optimal operating conditions, which were 30 °C and pH 7.5, favoring NOX stability. This work establishes a framework for the rational design and optimization of multi-enzymatic systems. It highlights the crucial interplay between individual enzyme properties and process conditions to achieve efficient and sustainable biocatalytic transformations. [ABSTRACT FROM AUTHOR]

Excellent oxygen barrier films were prepared by blending very small loadings (<1 wt%) of dihydroxyacetone (DHA), erythritol (ET) or xylitol (XT) in thermoplastic starch (TPS), and/or processing with supercritical carbon dioxide (scCO2) assistance. The minimum oxygen transmission rates (OTR) and all free-volume-hole characteristic (FVH) values of each scCO2-processed TPS/sugar alcohol film series are somewhat smaller than those of corresponding TPS/sugar alcohol film series without scCO2-assistance, and decrease with the decrease in sugar alcohol's molecular weight. The minimum OTR values acquired for scCO2-processed TPS/DHA and TPS/ET blown films are only 3.6 and 4.3 cm3/m2·day·atm, respectively, which meet the demand of high oxygen barrier films having OTR ≦5 cm3/m2·day·atm. The longitudinal or transversal tensile strengths acquired for each scCO2-processed TPS/sugar alcohol series films are ∼30 % to ∼40 % higher than those of the TPS blown films. Dynamic mechanical relaxations of each TPS/sugar alcohol or scCO2-processed TPS/sugar alcohol film series reveal that the sugar alcohols are compatible with TPS, as their sugar alcohol contents are ≤ the corresponding compatibility values. The decreased OTR and FVH values acquired for TPS/sugar alcohol or scCO2-processed TPS/sugar alcohol films are most likely due to them being scCO2-processed or incorporated with smaller molecular weight of sugar alcohols. [ABSTRACT FROM AUTHOR]

Background: Formaldehyde is a common cause of contact allergy. Hidden formaldehyde, that is, formaldehyde in products without formaldehyde releasers, has previously been detected in cosmetic products. Objectives: The objective of this study was to investigate the content and causes of hidden formaldehyde in leave‐on cosmetic products. Methods: The formaldehyde release from 142 cosmetic products, primarily creams, was analysed using the chromotropic acid (CA) method. The study included 130 products with no formaldehyde releasers on the ingredient list and 12 products with formaldehyde releasers. Products without formaldehyde releasers positive to CA, that is, with formaldehyde ≥2.5 ppm, were additionally analysed using high‐performance liquid chromatography (HPLC). Formaldehyde release from selected raw materials and packaging were also investigated. Results: Hidden formaldehyde was found in 23 of the 130 products (18%) without formaldehyde releasers on the ingredient list. The average formaldehyde content was 105 ppm (range: 0.5–507 ppm) in products with hidden formaldehyde and 355 ppm (range: 75–637 ppm) in eight products with formaldehyde releasers, selected for HPLC analysis. Impurities of formaldehyde in dihydroxyacetone may be a cause of hidden formaldehyde in self‐tanners. No clear pattern was found for the other products with hidden formaldehyde. Conclusions: Changes in regulation are needed to prevent allergic contact dermatitis from hidden formaldehyde in cosmetic products. [ABSTRACT FROM AUTHOR]

The concept of photoelectrochemical conversion of biomass into industrially valuable chemicals presents a compelling strategy to supplant the lower‐value oxygen evolution typically associated with photoanodes. Here, a surface potential manipulation method by regulating the surface oxygen valence states is put forward, which is demonstrated to be effective in enhancing the selective photoelectrochemical oxidation of glycerol to dihydroxyacetone (DHA). This involves the concurrent establishment of a BiVO4/CoOx heterojunction and a BiVO4/Au Schottky junction, aiming to fine‐tune the BiVO4 photoanode's surface potential and improve both its charge carrier separation and interfacial transfer kinetics. The BiVO4/CoOx/Au photoanode exhibits a photocurrent density of 6.15 mA cm−2 at 1.23 V versus reversible hydrogen electrode (RHE). Meanwhile, selective glycerol oxidation efficiency achieves a DHA evolution rate of 339.74 mmol m−2 h−1 and a selectivity exceeding 60%. Experiments and theoretical analysis underscore the pivotal role played by the surface potential in mediating glycerol and DHA adsorption and desorption processes. Additionally, the diminished surface potential attributed to the CoOx and Au amendments is responsible for the decreased Gibbs free energy of the dehydrogenation's rate‐limiting step involving the intermediate carbon species. This work demonstrates a method to design glycerol oxidation catalysts by modulating the interfacial molecular adsorption/desorption by surface potential regulation. [ABSTRACT FROM AUTHOR]

The waste glycerol generated during biodiesel production can be converted into a value-added product like dihydroxyacetone (DHA). DHA is widely applied in the cosmetic industry as a color additive in sunless tanning products. There is a market demand for DHA as the revenue for sunless tanning products is growing. Study on reviewing the viability of an industry-scaled DHA production plant is scarce. Therefore, it is the aim of this study to examine and evaluate the feasibility of the DHA production plant in terms of technical, economical, and safety aspects. In this present study, the DHA is synthesized from glycerol via microbial fermentation using Gluconobacter oxydans. The production process is designed and simulated using Aspen Plus software. Preliminary process hazards and safety reviews are conducted using HAZOP and process material risk assessment. Techno-economic and sensitivity analyses are also performed. The simulation results indicate that with 6266 tons of crude glycerol, 3871 tons of DHA can be generated annually. The DHA production from crude glycerol is found to be technically and economically viable. The DHA plant is able to retain profitability at ± 25% fluctuation of the DHA selling price, with a payback period of less than 5 years. The findings from this work provide insight into the feasibility of the valorization of waste crude glycerol from biodiesel synthesis into DHA. [ABSTRACT FROM AUTHOR]

The strain Gluconobacter oxydans LMG 1385 was used for the bioconversion of crude glycerol to dihydroxyacetone. The suitability of fed-batch cultures for the production of dihydroxyacetone was determined, and the influence of the pH of the culture medium and the initial concentration of glycerol on maximizing the concentration of dihydroxyacetone and on the yield and speed of obtaining dihydroxyacetone by bioconversion was examined. The feeding strategy of the substrate (crude glycerol) during the process was based on measuring the dissolved oxygen tension of the culture medium. The highest concentration of dihydroxyacetone PK = 175.8 g·L−1 and the highest yield YP/Sw = 94.3% were obtained when the initial concentration of crude glycerol was S0 = 70.0 g·L−1 and the pH of the substrate was maintained during the process at level 5.0. [ABSTRACT FROM AUTHOR]

Summary: Floral nectar composition beyond common sugars shows great diversity but contributing genetic factors are generally unknown. Mānuka (Leptospermum scoparium) is renowned for the antimicrobial compound methylglyoxal in its derived honey, which originates from the precursor, dihydroxyacetone (DHA), accumulating in the nectar. Although this nectar trait is highly variable, genetic contribution to the trait is unclear. Therefore, we investigated key gene(s) and genomic regions underpinning this trait.We used RNAseq analysis to identify nectary‐associated genes differentially expressed between high and low nectar DHA genotypes. We also used a mānuka high‐density linkage map and quantitative trait loci (QTL) mapping population, supported by an improved genome assembly, to reveal genetic regions associated with nectar DHA content.Expression and QTL analyses both pointed to the involvement of a phosphatase gene, LsSgpp2. The expression pattern of LsSgpp2 correlated with nectar DHA accumulation, and it co‐located with a QTL on chromosome 4. The identification of three QTLs, some of the first reported for a plant nectar trait, indicates polygenic control of DHA content.We have established plant genetics as a key influence on DHA accumulation. The data suggest the hypothesis of LsSGPP2 releasing DHA from DHA‐phosphate and variability in LsSgpp2 gene expression contributing to the trait variability. [ABSTRACT FROM AUTHOR]

Abstract Background Dihydroxyacetone (DHA) stands as a crucial chemical material extensively utilized in the cosmetics industry. DHA production through the dephosphorylation of dihydroxyacetone phosphate, an intermediate product of the glycolysis pathway in Escherichia coli, presents a prospective alternative for industrial production. However, insights into the pivotal enzyme, dihydroxyacetone phosphate dephosphorylase (HdpA), remain limited for informed engineering. Consequently, the development of an efficient tool for high-throughput screening of HdpA hypermutants becomes imperative. Results This study introduces a methylglyoxal biosensor, based on the formaldehyde-responding regulator FrmR, for the selection of HdpA. Initial modifications involved the insertion of the FrmR binding site upstream of the −35 region and into the spacer region between the −10 and −35 regions of the constitutive promoter J23110. Although the hybrid promoter retained constitutive expression, expression of FrmR led to complete repression. The addition of 350 μM methylglyoxal promptly alleviated FrmR inhibition, enhancing promoter activity by more than 40-fold. The methylglyoxal biosensor system exhibited a gradual increase in fluorescence intensity with methylglyoxal concentrations ranging from 10 to 500 μM. Notably, the biosensor system responded to methylglyoxal spontaneously converted from added DHA, facilitating the separation of DHA producing and non-producing strains through flow cytometry sorting. Subsequently, the methylglyoxal biosensor was successfully applied to screen a library of HdpA mutants, identifying two strains harboring specific mutants 267G > T and D110G/G151C that showed improved DHA production by 68% and 114%, respectively. Expressing of these two HdpA mutants directly in a DHA-producing strain also increased DHA production from 1.45 to 1.92 and 2.29 g/L, respectively, demonstrating the enhanced enzyme properties of the HdpA mutants. Conclusions The methylglyoxal biosensor offers a novel strategy for constructing genetically encoded biosensors and serves as a robust platform for indirectly determining DHA levels by responding to methylglyoxal. This property enables efficiently screening of HdpA hypermutants to enhance DHA production.

Abstract Background Formolase (FLS) is a computationally designed enzyme that catalyzes the carboligation of two or three C1 formaldehyde molecules into C2 glycolaldehyde or C3 dihydroxyacetone (DHA). FLS lays the foundation for several artificial carbon fixation and valorization pathways, such as the artificial starch anabolic pathway. However, the application of FLS is limited by its low catalytic activity and product promiscuity. Findings FLS, designed and engineered based on benzoylformate decarboxylase from Pseudomonas putida, was selected as a candidate for modification. To evaluate its catalytic activity, 25 residues located within an 8 Å distance from the active center were screened using single-point saturation mutagenesis. A screening approach based on the color reaction of the DHA product was applied to identify the desired FLS variants. After screening approximately 5,000 variants (approximately 200 transformants per site), several amino acid sites that were not identified by directed evolution were found to improve DHA formation. The serine-to-phenylalanine substitution at position 236 improved the activity towards DHA formation by 7.6-fold. Molecular dynamics simulations suggested that the mutation increased local hydrophobicity at the active site, predisposing the cofactor-C2 intermediate to nucleophilic attack by the third formaldehyde molecule for subsequent DHA generation. Conclusions This study provides improved FLS variants and valuable information into the influence of residues adjacent to the active center affecting catalytic efficiency, which can guide the rational engineering or directed evolution of FLS to optimize its performance in artificial carbon fixation and valorization.

Background: Dihydroxyacetone (DHA) stands as a crucial chemical material extensively utilized in the cosmetics industry. DHA production through the dephosphorylation of dihydroxyacetone phosphate, an intermediate product of the glycolysis pathway in Escherichia coli, presents a prospective alternative for industrial production. However, insights into the pivotal enzyme, dihydroxyacetone phosphate dephosphorylase (HdpA), remain limited for informed engineering. Consequently, the development of an efficient tool for high-throughput screening of HdpA hypermutants becomes imperative. Results: This study introduces a methylglyoxal biosensor, based on the formaldehyde-responding regulator FrmR, for the selection of HdpA. Initial modifications involved the insertion of the FrmR binding site upstream of the −35 region and into the spacer region between the −10 and −35 regions of the constitutive promoter J23110. Although the hybrid promoter retained constitutive expression, expression of FrmR led to complete repression. The addition of 350 μM methylglyoxal promptly alleviated FrmR inhibition, enhancing promoter activity by more than 40-fold. The methylglyoxal biosensor system exhibited a gradual increase in fluorescence intensity with methylglyoxal concentrations ranging from 10 to 500 μM. Notably, the biosensor system responded to methylglyoxal spontaneously converted from added DHA, facilitating the separation of DHA producing and non-producing strains through flow cytometry sorting. Subsequently, the methylglyoxal biosensor was successfully applied to screen a library of HdpA mutants, identifying two strains harboring specific mutants 267G > T and D110G/G151C that showed improved DHA production by 68% and 114%, respectively. Expressing of these two HdpA mutants directly in a DHA-producing strain also increased DHA production from 1.45 to 1.92 and 2.29 g/L, respectively, demonstrating the enhanced enzyme properties of the HdpA mutants. Conclusions: The methylglyoxal biosensor offers a novel strategy for constructing genetically encoded biosensors and serves as a robust platform for indirectly determining DHA levels by responding to methylglyoxal. This property enables efficiently screening of HdpA hypermutants to enhance DHA production. [ABSTRACT FROM AUTHOR]

Background: Formolase (FLS) is a computationally designed enzyme that catalyzes the carboligation of two or three C1 formaldehyde molecules into C2 glycolaldehyde or C3 dihydroxyacetone (DHA). FLS lays the foundation for several artificial carbon fixation and valorization pathways, such as the artificial starch anabolic pathway. However, the application of FLS is limited by its low catalytic activity and product promiscuity. Findings: FLS, designed and engineered based on benzoylformate decarboxylase from Pseudomonas putida, was selected as a candidate for modification. To evaluate its catalytic activity, 25 residues located within an 8 Å distance from the active center were screened using single-point saturation mutagenesis. A screening approach based on the color reaction of the DHA product was applied to identify the desired FLS variants. After screening approximately 5,000 variants (approximately 200 transformants per site), several amino acid sites that were not identified by directed evolution were found to improve DHA formation. The serine-to-phenylalanine substitution at position 236 improved the activity towards DHA formation by 7.6-fold. Molecular dynamics simulations suggested that the mutation increased local hydrophobicity at the active site, predisposing the cofactor-C2 intermediate to nucleophilic attack by the third formaldehyde molecule for subsequent DHA generation. Conclusions: This study provides improved FLS variants and valuable information into the influence of residues adjacent to the active center affecting catalytic efficiency, which can guide the rational engineering or directed evolution of FLS to optimize its performance in artificial carbon fixation and valorization. [ABSTRACT FROM AUTHOR]

Measuring the tanning skin can provide a scientific method to evaluate the efficacy of cosmetics exfoliator. Dihydroxyacetone (DHA, 5.0% (w/w)) was used to stain the inner forearms cuticle of subjects. The skin surface L*and b* were determined, then ITA and its recovery rate were calculated to evaluate the exfoliating efficacy of cosmetics. The results showed that no significant (P≥0.05) differences were observed for L*, b* and ITA on different skin surface of unstained subjects. After staining with DHA, no adverse reaction was found in the stained areas, and the changes of L*, b* and ITA on different skin surface were consistent (P≥0.05). Two different cosmetics were used continuously to exfoliate the skin in different areas. After treatment for 7 days, L*, b* and ITA of the corresponding skin areas had significant (P<0.05) improvement in comparison with the negative control area. But there were differences in the evaluation results of the exfoliating efficacy using these three parameters. The recovery rate of ITA of two samples improved significantly (P<0.05) than the negative control area. The work indicates that using 5.0% DHA for skin browning and measuring the skin surface color change by ITA recovery rate can accurately and sensitively assess the skin cuticle renewal rate. This method can be used as one of the effective ways to evaluate the exfoliating efficacy of cosmetics. [ABSTRACT FROM AUTHOR]

Glycerol dehydrogenase (GDH) catalyzes glycerol oxidation to dihydroxyacetone in a NAD+-dependent manner. As an initiator of the oxidative pathway of glycerol metabolism, a variety of functional and structural studies of GDH have been conducted previously. Structural studies revealed intriguing features of GDH, like the flexible β-hairpin and its significance. Another commonly reported structural feature is the enzyme's octameric oligomerization, though its structural details and functional significance remained unclear. Here, with a newly reported GDH structure, complexed with both NAD+ and glycerol, we analyzed the octamerization of GDH. Structural analyses revealed that octamerization reduces the structural dynamics of the N-domain, which contributes to more consistently maintaining a distance required for catalysis between the cofactor and substrate. This suggests that octamerization may play a key role in increasing the likelihood of the enzyme reaction by maintaining the ligands in an appropriate configuration for catalysis. These findings expand our understanding of the structure of GDH and its relation to the enzyme's activity. [ABSTRACT FROM AUTHOR]

Catalytic conversion of glucose to lactic acid is a green promising strategy for the effective utilization of biomass‐derived carbohydrates to generate valuable chemicals. The generation of lactic acid would also be distinguishing in different reaction atmospheres. In this work, we firstly investigated the decomposition of lactic acid and glucose transformation to lactic acid in H2. No obvious decomposition of lactic acid was observed in H2. The activity testing results showed that glucose could be completely converted over the selected hydroxides, while the formation of lactic acid was closely related to the alkalinity of hydroxide. The yield of lactic acid was remarkably obtained to be 87 % over Ca(OH)2 at 220 °C for 3 h. Stronger alkalinity of the catalyst would facilitate glucose isomerization to fructose, and then easily be transformed into dihydroxyacetone or glyceraldehyde intermediates through reverse aldol condensation, which is beneficial to the generation of lactic acid. [ABSTRACT FROM AUTHOR]

KDO (2-keto-3-deoxy-D-manno-octulosonate) is a landmark molecule of the Gram-negative outer membrane. Mutants without KDO formation are known to be barely viable. Arabinose 5-phosphate (A5P) is a precursor of KDO biosynthesis and is normally derived from ribulose 5-phosphate by A5P isomerases, encoded by kdsD and gutQ genes in E. coli K-12. We created a kdsD gutQ-deficient double mutant of strain BW25113 and confirmed that these cells are A5P auxotrophs. Fructose 6-phosphate aldolase (FSA) is known to utilize (among other donors such as dihydroxyacetone or hydroxyacetone) glycolaldehyde (GoA) as a donor compound and to provide A5P in vitro when glyceraldehyde 3-phosphate is the acceptor. We show here that this FSA function in vivo fully reverses the growth defect and the A5P deficiency in kdsD gutQ double mutants. Expression of both plasmid-encoded fsaA, fsaAA129S, or fsaB genes as well as a chromosomally integrated form of fsaAA129S led to maximal OD600 values of >2.2 when GoA was added exogenously (together with glucose as a C source) at a concentration of 100 µM (Ks values in the range of 4–10 µM). Thus, a novel bio-orthogonal bypass to overcome an A5P deficiency was opened. Lower GoA concentrations led to lower growth yields. Interestingly, mutant strains with recombinant fsa genes showed considerable growth yields even without exogenous GoA addition, pointing to yet unknown endogenous GoA sources in E. coli metabolism. This is a further example of the usefulness of FSA in rewiring central metabolic pathways in E. coli. [ABSTRACT FROM AUTHOR]

Diabetic kidney disease (DKD) can lead to accumulation of glucose upstream metabolites due to dysfunctional glycolysis. But the effects of accumulated glycolysis metabolites on podocytes in DKD remain unknown. The present study examined the effect of dihydroxyacetone phosphate (DHAP) on high glucose induced podocyte pyroptosis. By metabolomics, levels of DHAP, GAP, glucose‐6‐phosphate and fructose 1, 6‐bisphosphate were significantly increased in glomeruli of db/db mice. Furthermore, the expression of LDHA and PKM2 were decreased. mRNA sequencing showed upregulation of pyroptosis‐related genes (Nlrp3, Casp1, etc.). Targeted metabolomics demonstrated higher level of DHAP in HG‐treated podocytes. In vitro, ALDOB expression in HG‐treated podocytes was significantly increased. siALDOB‐transfected podocytes showed less DHAP level, mTORC1 activation, reactive oxygen species (ROS) production, and pyroptosis, while overexpression of ALDOB had opposite effects. Furthermore, GAP had no effect on mTORC1 activation, and mTORC1 inhibitor rapamycin alleviated ROS production and pyroptosis in HG‐stimulated podocytes. Our findings demonstrate that DHAP represents a critical metabolic product for pyroptosis in HG‐stimulated podocytes through regulation of mTORC1 pathway. In addition, the results provide evidence that podocyte injury in DKD may be treated by reducing DHAP. [ABSTRACT FROM AUTHOR]

The human gut is an anoxic environment that harbours a multitude of microorganisms that not only contribute to food digestion. The microbiome is also involved in malfunctions such as diseases, inflammation processes or development of obesity, but it is also involved in processes that increase the human well‐being. Both, the good and the bad, are mediated by fermentation end products of bacterial metabolism, among others. However, despite a steadily growing knowledge of 'who lives out there', little in known of 'what do they do out there'. The genus Blautia is commonly found in the gut and associated with human well‐being, but the exploration of their metabolic potential has just started. We demonstrate that B. schinkii grows on glycerol by producing acetate and ethanol. Transcriptome studies and biochemical analyses revealed a glycerol dehydrogenase and dihydroxyacetone kinase that funnel the substrate into glycolysis. Consequently, cells also grew on dihydroxyacetone. Cells could be adapted to grow at high (up to 1.5 M) glycerol concentrations but then only ethanol was formed. Ethanol production from glycerol is not only of relevance for the human host but also for potential bioindustrial production of bioethanol from waste glycerol. [ABSTRACT FROM AUTHOR]

The strain Gluconobacter oxydans LMG 1385 was used for the bioconversion of crude glycerol to dihydroxyacetone. The suitability of fed-batch cultures for the production of dihydroxyacetone was determined, and the influence of the pH of the culture medium and the initial concentration of glycerol on maximizing the concentration of dihydroxyacetone and on the yield and speed of obtaining dihydroxyacetone by bioconversion was examined. The feeding strategy of the substrate (crude glycerol) during the process was based on measuring the dissolved oxygen tension of the culture medium. The highest concentration of dihydroxyacetone PK = 175.8 g·L−1 and the highest yield YP/Sw = 94.3% were obtained when the initial concentration of crude glycerol was S0 = 70.0 g·L−1 and the pH of the substrate was maintained during the process at level 5.0.

Dihydroxyacetone isomerization is a fundamental reaction for the production of lactic acid using different feedstocks. However, achieving excellent catalytic activity and resistance against leaching in water is challenging. Herein, we devised a Sn doped zirconium phosphate as effective heterogeneous catalyst. The incorporation of Sn could remarkably aggrandize the content of strong Lewis acid sites while retain relatively high surface areas. Gratifyingly, this catalyst exhibits enhanced activity and reusability for selective dihydroxyacetone isomerization into lactic acid with water as solvent. High lactic acid yields of 70.30 and 76.25% were achieved in water and water/acetone under optimal reaction conditions, respectively. The composition and activity of catalyst are reserved with reduced ions leaching. The excellent catalytic performance is attributed to accelerated conversion of pyruvaldehyde to lactic acid by the strong Lewis acid sites. Nuclear magnetic resonance revealed that the reaction is proceeded via a keto-enol tautomerization process.

Dihydroxyacetone (DHA) occurs in wide-ranging organisms, including plants, and can undergo spontaneous conversion to methylglyoxal (MG). While the toxicity of MG to plants is well-known, the toxicity of DHA to plants remains to be elucidated. We investigated the effects of DHA and MG on Arabidopsis. Exogenous DHA at up to 10 mm did not affect the radicle emergence, the expansion of green cotyledons, the seedling growth, or the activity of glyoxalase II, while DHA at 10 mm inhibited the root elongation and increased the activity of glyoxalase I. Exogenous MG at 1.0 mm inhibited these physiological responses and increased both activities. Dihydroxyacetone at 10 mm increased the MG content in the roots. These results indicate that DHA is not so toxic as MG in Arabidopsis seeds and seedlings and suggest that the toxic effect of DHA at high concentrations is attributed to MG accumulation by the conversion to MG. Is dihydroxyacetone toxic in Arabidopsis? [ABSTRACT FROM AUTHOR]

Sunless tanning products have risen in popularity as the desire for a tanned appearance continues alongside growing concerns about the deleterious effects of ultraviolet radiation exposure from the sun. Dihydroxyacetone (DHA) is a simple carbohydrate found nearly universally in sunless tanning products that serves to impart color to the skin. The Food and Drug Administration (FDA), which regulates sunless tanning products as cosmetics, allows DHA for external use while maintaining that its ingestion, inhalation, or contact with mucosal surfaces should be avoided. Given its widespread use and a paucity of reviews on its safety, we aim to review the literature on the topical properties and safety profile of DHA. Available data indicate that DHA possesses only minimal to no observable photoprotective properties. In vitro studies suggest that, while DHA concentrations much higher than those in sunless tanning products are needed to induce significant cytotoxicity, even low millimolar, nonlethal concentrations can alter the function of keratinocytes, tracheobronchial cells, and other cell types on a cellular and molecular level. Instances of irritant and allergic contact dermatitis triggered by DHA exposures have also been reported. While no other side effects in humans have been observed, additional studies on the safety and toxicity of DHA in humans are warranted, with a focus on concentrations and frequencies of DHA exposure typically encountered by consumers. [ABSTRACT FROM AUTHOR]

The conversion of dihydroxyacetone solution in methanol to methyl lactate has been studied in flow regime using xSnO2/Al2O3-supported catalysts that have been characterized by XRD, low-temperature nitrogen (ad)desorption analysis, and UV-Vis spectroscopy. It is found that Lewis and Brønsted acid sites of the surface of SnO2-containing catalysts play a crucial role in the selective conversion of dihydroxyacetone to methyl lactate. The formation of methyl lactate with a selectivity of 90% is achieved on 5%SnO2/Al2O3 catalyst at 160°C, 1.0 MPa, and under feed rate of 4 mmol C3H6O3/(gcat·h). [ABSTRACT FROM AUTHOR]

Background and Aim: Aluminum phosphide poisoning has a high mortality rate because of the production of phosphine gas and refractory hypotension. Based on the effect of dihydroxyacetone on the treatment of hypotension and reduction of cytochrome C oxidase, the effects of dihydroxyacetone on the level of oxidative stress factors and histology of heart and liver tissue in aluminum phosphide-poisoned male rats were investigated. Materials and Methods: In this study, 24 rats were randomly divided into 4 groups including control (corn oil), aluminum phosphide (15 mg/kg), dihydroxyacetone (50 mg/kg) and also poisoned and treated group (aluminum phosphide (15 mg/kg) + dihydroxyacetone (50 mg/kg)). After 24 hours, the animals were sacrificed and the blood, plasma, heart, and liver samples were collected then oxidative stress factors and histology of the heart and liver were investigated. Results: Aluminum phosphide poisoning increased lipid peroxidation in red blood cells (p=0.001) and liver tissue (p=0.023) and also increased protein carbonylation in plasma (p =0.005) and red blood cells (p=0.001). After administration of dihydroxyacetone, lipid peroxidation in red blood cells (p=0.001) and liver (p=0.001) and carbonylation of proteins in red blood cells (p=0.003) and plasma (p=0.019) decreased. No significant change was observed in total plasma antioxidant capacity, carbonylation levels of the liver and heart, and lipid peroxidation in heart tissue. In addition, treatment with dihydroxyacetone significantly improved the histological changes in liver and heart tissue. Conclusion: Dihydroxyacetone not only prevents phosphine-induced deaths but also improves oxidative stress and histology of liver and heart tissue.

Different soft chemical syntheses were applied to synthesize eight Nb2O5 catalysts that were fully characterized in terms of structure, porosity, surface acidity and catalytic performance. The results showed that the catalysts indeed presented different structures and acidity. The distorted orthorhombic phase rendered solids with an improved porosity and allowed tuning higher concentrations of water-tolerant Lewis acid sites and higher Brønsted acidity when compared to a more crystalline pseudohexagonal phase. Catalysts holding the distorted orthorhombic structure were more active and selective to chemoconversion of trioses into lactic acid. It was shown though that product distribution was far more sensitive to changes in crystalline structure and Lewis acidity in the cascade reaction than the overall catalytic activity. A consistent linear correlation was found between lactic acid selectivity and the amount of water-tolerant Lewis acid sites, disclosing their dependence. It is the first time that such a clear correlation is demonstrated for triose upgrading cascade reaction. [ABSTRACT FROM AUTHOR]

Pt/La1−xBixOF/SBA-16 (SBA-16: Santa Barbara Amorphous no. 16) catalysts were prepared to produce dihydroxyacetone (DHA) from glycerol under moderate conditions. By using 7 wt% Pt/16 wt% La0.95Bi0.05OF/SBA-16, the DHA yield reached up to 78.4% (glycerol conversion: 100%) after reacting for 6 h at 30 °C in an atmospheric open-air system. [ABSTRACT FROM AUTHOR]

{111}-Dominated octahedral Co 3 O 4 electrocatalyst with better adsorption performance and enhanced electron transfer exhibited good catalytic activity and high selectivity for glycerol oxidation to high-value-added chemical, i.e., dihydroxyacetone (DHA). [Display omitted] • Successful synthesis of the {111}- and {001}-dominant Co 3 O 4 electrodes. • First report of crystal engineering for the oxidation of glycerol using spinnel cobalt oxide (Co 3 O 4). • {111}-dominant octahedral Co 3 O 4 plane exhibits superior activity for glycerol oxidation. • Improved reactant adsorption, and charge transfer across distinct Co 3 O 4 facets all affect activity. To further explore the electrooxidation mechanism of biomass-based compounds, it is highly desirable to regulate the proportion of reactive facets and identify facet-governing reactivity through crystal facet engineering. In this study, octahedral and cubic cobalt spinel oxide (Co 3 O 4), each exclusively exposed by one specific type of facet, are selected as two representative microstructure models for tuning the selectivity and productivity of electrochemical glycerol oxidation reaction. The results indicate that the {111}-dominant octahedral Co 3 O 4 plane with a higher population of Co2+ sites exhibits superior electrocatalytic activity for glycerol oxidation compared with the {001}-dominant cubic Co 3 O 4 , allowing nearly 65% of glycerol to be converted into a high-value-added dihydroxyacetone (DHA) compound. The average DHA production rate over octahedral Co 3 O 4 (2.5 μmol cm−2h−1) are approximately 3.5 times greater than that over cubic Co 3 O 4 (0.7 μmol cm−2h−1). Electrochemical studies and surface atomic configuration analysis reveal that {111}-dominant octahedral Co 3 O 4 with a higher density of active cobalt ion yields unique reactant adsorption and charge transfer, leading to increased glycerol oxidation reactivity and productivity. The present study emphasizes the significance of controlling the highly active facet in developing efficient and selective electrocatalysts. [ABSTRACT FROM AUTHOR]

We reported a strategy of carbon‐negative H2 production in which CO2 capture was coupled with H2 evolution at ambient temperature and pressure. For this purpose, carbonate‐type CuxMgyFez layered double hydroxide (LDH) was preciously constructed, and then a photocatalysis reaction of interlayer CO32− reduction with glycerol oxidation was performed as driving force to induce the electron storage on LDH layers. With the participation of pre‐stored electrons, CO2 was captured to recover interlayer CO32− in presence of H2O, accompanied with equivalent H2 production. During photocatalysis reaction, Cu0.6Mg1.4Fe1 exhibited a decent CO evolution amount of 1.63 mmol g−1 and dihydroxyacetone yield of 3.81 mmol g−1. In carbon‐negative H2 production process, it showed an exciting CO2 capture quantity of 1.61 mmol g−1 and H2 yield of 1.44 mmol g−1. Besides, this system possessed stable operation capability under simulated flu gas condition with negligible performance loss, exhibiting application prospect. [ABSTRACT FROM AUTHOR]

1,3-dihydroxyacetone (DHA) is an underrated bio-based synthon, with a broad range of reactivities. It is produced for the revalorization of glycerol, a major side-product of the growing biodiesel industry. The overwhelming majority of DHA produced worldwide is intended for application as a self-tanning agent in cosmetic formulations. This review provides an overview of the discovery, physical and chemical properties of DHA, and of its industrial production routes from glycerol. Microbial fermentation is the only industrial-scaled route but advances in electrooxidation and aerobic oxidation are also reported. This review focuses on the plurality of reactivities of DHA to help chemists interested in bio-based building blocks see the potential of DHA for this application. The handling of DHA is delicate as it can undergo dimerization as well as isomerization reactions in aqueous solutions at room temperature. DHA can also be involved in further side-reactions, yielding original side-products, as well as compounds of interest. If this peculiar reactivity was harnessed, DHA could help address current sustainability challenges encountered in the synthesis of speciality polymers, ranging from biocompatible polymers to innovative polymers with cutting-edge properties and improved biodegradability. [ABSTRACT FROM AUTHOR]

Abstract Catalytic valorization of raw glycerol derived from biodiesel into high-value chemicals has attracted great attention. Here, we report chemoenzymatic cascade reactions that convert glycerol to lactic acid and glycolic acid. In the enzymatic step, a coenzyme recycling system was developed to convert glycerol into 1,3-dihydroxyacetone (DHA) with a yield of 92.3% in potassium phosphate buffer (300 mM, pH 7.1) containing 100 mM glycerol, 2 mM NAD+, 242 U/mL glycerol dehydrogenase-GldA and NADH oxidase-SpNoxK184R at 30 °C. Subsequently, NaOH or NaClO2 catalyzes the formation of lactic acid and glycolic acid from DHA. The high yield of lactic acid (72.3%) and glycolic acid (78.2%) verify the benefit of the chemoenzymatic approaches. Graphical Abstract

A set of catalysts based on the mixed Cu-Co oxide supported on a porous dealuminized metakaolinite was synthesized and evaluated in the partial oxidation of glycerol under greener conditions. The characterization results confirmed the formation of an inverse spinel structure (CuCo2O4) as the active phase. High glycerol conversion (70.6%) and selectivity to dihydroxyacetone (88.2%) were obtained at 80 °C and 1:2 glycerol:H2O2 molar ratio, after 4 h of reaction, using a metal load of 10 wt% on the support. The catalytic activity results suggest that this reaction is sensitive to the metal oxide particle size, but the selectivity is unaffected.

The application of bio‐derived feedstocks as building blocks in organic syntheses holds great value with goals of high product yield and minimizing carbon loss. As contribution to this effort, present work explores 5 different C2‐ and C3‐feedstocks (derived from biomass and conventional sources) such as glycerol (GLY), 1,3‐dihydroxyacetone (DHA), ethylene glycol (EG), glycolic acid (GLYAC) and glyoxal (GLYOX) as carbon sources for highly selective, catalyst‐free oxidative synthesis of N‐formamides from primary and secondary amines. Both DHA and GLYOX showed the best carbon efficiency through carbon source: amine ratio of 1 : 2, resulting in 100 % selectivity of N‐formanilide with tert‐butyl hydrogen peroxide (TBHP) as the oxidant. GLYOX was applied further for synthesizing a N‐formamide library of 21 substrates exemplifying substantial yields ranging from 68–98 %. Moreover, pilot scalability of this methodology achieved a yield of 87 % and 72 % for aniline substrate at 5‐gram scale using GLYOX and DHA respectively in 24 hours. [ABSTRACT FROM AUTHOR]

As the desire and popularity of a tanned appearance continues, the social effects of UV‐free tanning are becoming more important. Dihydroxyacetone (DHA) has seen extensive use as the main tanning agent in sunless tanners. The DHA‐induced tan is a result of brown melanoidins formed by a non‐enzymatic Maillard reaction between DHA and amino acid species found in the stratum corneum. DHA, thereby, provides a safer route to a tanned appearance compared with exposure to ultraviolet radiation. However, DHA is a highly reactive molecule, posing a multitude of challenges for potential product formulations. With their increased use, the safety considerations of topically applied DHA tanners have been investigated. Many different vehicles have been used for topical delivery of DHA, and they are becoming increasingly multifunctional. This review provides a holistic overview of dihydroxyacetone sunless tanning products. [ABSTRACT FROM AUTHOR]

In this paper, evidence is provided that the model reaction of aqueous dihydroxyacetone (DHA) conversion is as sensitive to the TiO2 catalysts' basicity as to their acidity. Two parallel pathways transformed DHA: while the pathway catalyzed by Lewis acid sites gave pyruvaldehyde (PA) and lactic acid (LA), the base-catalyzed route afforded fructose. This is demonstrated on a series of six commercial TiO2 samples and further confirmed by using two reference catalysts: niobic acid (NbOH), an acid catalyst, and a hydrotalcite (MgAlO), a basic catalyst. The original acid-base properties of the six commercial TiO2 with variable structure and texture were investigated first by conventional methods in gas phase (FTIR or microcalorimetry of pyridine, NH3 and CO2 adsorption). A linear relationship between the initial rates of DHA condensation into hexoses and the total basic sites densities is highlighted accounting for the water tolerance of the TiO2 basic sites whatever their strength. Rutile TiO2 samples were the most basic ones. Besides, only the strongest TiO2 Lewis acid sites were shown to be water tolerant and efficient for PA and LA formation. [ABSTRACT FROM AUTHOR]

The catalytic behaviors of various tin compounds for the conversion of 1,3-dihydroxyacetone (DHA) to methyl lactate (ML) in methanol, as well as the reaction process, were briefly investigated in a batch reactor. The results indicated that metal cations with strong Lewis acidity, in particular Sn2+ and Sn4+, catalyzed efficiently the conversion of DHA to ML. The performance of tin cation was closely related to its counterpart anions, with the halide anions (Cl- and Br-) acting as promoters. Besides, high temperature favored the yield of methyl lactate when SnCl2 served as a catalyst, yielding the DHA conversion and ML selectivity of 98.2% and of 96.0% respectively at 100℃ Moreover, the evolution of reaction products against time suggested that the conversion of DHA to ML proceeded through a combination of consecutive and parallel reaction steps. Pyruvic aldehyde hemiacetal was the detectable reaction intermediate, whereas ML proved to be final products. [ABSTRACT FROM AUTHOR]

Alkalized CN photocatalyst with potassium doping is rationally designed to realize selective co-production of dihydroxyacetone and glyceric acid, resulting in >70 % glycerol conversion and >70 % total selectivity from glycerol photo-oxidation process. [Display omitted] • The alkalized CN with K doping is synthesized via a facile calcination process. • Co-production of dihydroxyacetone and glyceric acid via glycerol photo-oxidation. • Glycerol conversion (>80 %) and co-production selectivity (>70 %) can be achieved. • Superior performance of modified CN for glycerol oxidation is demonstrated by DFT. The emergence of biomass valorization holds great promise in tackling the energy crisis and promote carbon neutrality. Mild and cost-effective photocatalysis offers notable advantages in terms of energy efficiency, environmentally friendly, and facile processes. Here, we demonstrate selective glycerol photo-oxidation for dihydroxyacetone (DHA) and glyceric acid (GLA) co-production by strategically engineering potassium-doped alkalized polymeric carbon nitride (CN). The altered CN demonstrates promoted absorption of visible light, increased efficiency in separating charges, and superior deprotonating functionality of glycerol. Density functional theory (DFT) calculations further certificate its superior performance for glycerol oxidation into DHA and GLA. As a result, the rationally-constructed CN achieves exceptional glycerol conversion (>70 %) and maintains total selectivity of DHA and GLA (>70 %) at room temperature. This study showcases the viability of selective glycerol photo-oxidation for co-production of high-value chemicals under mild operating conditions. [ABSTRACT FROM AUTHOR]

[Display omitted] • In-situ Raman tracking NiOx surface evolution, especially for the broadening band around 900 – 1200 cm-1. • Enhancing catalytic activity and selectivity of 3-carbon product through borate-polyol chelate. • Controlling five-member or six-member ring complex formation by varying borate/glycerol ratio. • Effect of borate/glycerol ratio on tuning selective oxidation of primary or secondary alcohol group. Controlling selective glycerol electrooxidation towards the primary or secondary alcohol group, which enables obtained dihydroxyacetone or glyceraldehyde as the main product, is a challenge for an effective glycerol electrolysis system. In this work, we systematically investigated the protective effect of borate-glycerol complexes toward primary and secondary alcohol group oxidation during the glycerol electrooxidation process on NiO x catalyst in borate buffer (pH 9.2). The Raman spectroscopy and high-performance liquid chromatography results indicated that manipulating the borate/glycerol (B/G) ratio could affect selective oxidation towards primary or secondary alcohol group. Five-member ring complex was more likely to form in the electrolyte with the B/G ratio of 0.1, whereas six-member ring complex became more significant in the electrolyte with the B/G ratio of 1.5. The dominance of five- or six-member ring complex could enhance the favored adsorption of primary or secondary alcohol group, thus generating glyceraldehyde or dihydroxyacetone as the main product, respectively. The results in this study highlight the significance of electrolyte property on glycerol electrocatalysis, which is universally applicable to other transition metal electrocatalysts, enabling the development of a highly selective glycerol electrooxidation towards primary or secondary alcohol system at near-neutral pH level. [ABSTRACT FROM AUTHOR]

The electrocatalytic valorization of glycerol is an emerging upcycling process for the biomass utilization. In this work, nickel/sulfur-codoped laser-induced graphene (LINiSG) on flexible polyimide film was fabricated and demonstrated as a self-supported and binder-free monolithic electrode for electrocatalytic glycerol oxidation reaction (EGOR) towards the selective generation of value-added three-carbon (C3) chemicals. The laser-induced in-situ and synchronous carbonization of polysulfone and Ni precursor was demonstrated to remarkably promote both the electrochemical surface area and Ni loading of LINiSG electrode. These synergistic merits are considered as the main origin for its enhanced EGOR activity and stability, showing much smaller Tafel slope and 2-fold enhanced current density, as compared to LINiG electrode without the co-carbonization of polysulfone. The influence of experimental parameters has been systematically investigated by the product analysis, achieving an average 94.7 % C3 selectivity and 76.1 % C3 Faradaic efficiency with a high selectivity of dihydroxyacetone (ca. 67.7 %) in near-neutral conditions, which is better than most of the reported EGOR electrodes operated in near-neutral conditions. This work demonstrated the viability of using flexible self-supported and binder-free LIG electrode with rational design and preparation approach for electrocatalytic valorization of biomass. [Display omitted] • First report of the self-supported LIG for electrochemical glycerol valorization. • Binder-free Ni/S-codoped LIG electrode was prepared by a facile laser-scribing method. • Laser-induced co-carbonization promoted the activity of glycerol oxidation. • Activity and products of glycerol oxidation under different conditions are studied. • DHA/C3 production achieve the selectivity of 67.7 %/94.7 % at near-neutral conditions. [ABSTRACT FROM AUTHOR]

• The Ag, Cu, and Cu-Ag nanoparticles decrease the Ban-gap of TiO 2 (P25). • Partial glycerol oxidation was achieved using a low-wattage (1.8 W) LED white lamp. • The as-prepared catalyst absorbs efficiently in the visible region. • The Ag/TiO 2 was the most active catalyst due to the Schottky-type activation. • The selectivity to dihydroxyacetone shows that glycerol is selectively oxidized. A set of catalysts was prepared by the surface decoration of TiO 2 (Degussa-P25) with noble metal (Ag), non-noble metal (Cu), and bimetallic (Cu-Ag) nanoparticles, which were evaluated for photocatalytic glycerol oxidation under low-wattage irradiation (commercial-led white light, 1.8 W), basic free conditions and the assistance of hydrogen peroxide. Dihydroxyacetone and glyceraldehyde were obtained as the primary oxidation products. After 8 h, the Ag/TiO 2 catalyst showed the highest photocatalytic activity (glycerol conversion of 74%) and dihydroxyacetone selectivity of 80%. However, the highest selectivity toward dihydroxyacetone (86%) was achieved with the Cu/TiO 2 catalyst for a glycerol conversion of 55%. Thus, the results confirm the crucial role of nanoparticles in inducing a surface plasmon resonance effect (Schottky junction for metallic Ag) and a heterojunction effect (for CuO and Cu 2 O) that allows light absorption within the visible region. [Display omitted] [ABSTRACT FROM AUTHOR]

PurposeAlthough 1 H spin coupling is generally avoided in probes for hyperpolarized (HP) 13 C MRI, enzymatic transformations of biological interest can introduce large 13 C-1 H couplings in vivo. The purpose of this study was to develop and investigate the application of 1 H decoupling for enhancing the sensitivity for detection of affected HP 13 C metabolic products.MethodsA standalone 1 H decoupler system and custom concentric 13 C/1 H paddle coil setup were integrated with a clinical 3T MRI scanner for in vivo 13 C MR studies using HP [2-13 C]dihydroxyacetone, a novel sensor of hepatic energy status. Major 13 C-1 H coupling JCH  = ∼150 Hz) is introduced after adenosine triphosphate-dependent enzymatic transformation of HP [2-13 C]dihydroxyacetone to [2-13 C]glycerol-3-phosphate in vivo. Application of WALTZ-16 1 H decoupling for elimination of large 13 C-1 H couplings was first tested in thermally polarized glycerol phantoms and then for in vivo HP MR studies in three rats, scanned both with and without decoupling.ResultsAs configured, 1 H-decoupled 13 C MR of thermally polarized glycerol and the HP metabolic product [2-13 C]glycerol-3-phosphate was achieved at forward power of approximately 15 W. High-quality 3-s dynamic in vivo HP 13 C MR scans were acquired with decoupling duty cycle of 5%. Application of 1 H decoupling resulted in sensitivity enhancement of 1.7-fold for detection of metabolic conversion of [2-13 C]dihydroxyacetone to HP [2-13 C]glycerol-3-phosphate in vivo.ConclusionsApplication of 1 H decoupling provides significant sensitivity enhancement for detection of HP 13 C metabolic products with large 1 H spin couplings, and is therefore expected to be useful for preclinical and potentially clinical HP 13 C MR studies. Magn Reson Med 80:36-41, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

AimsHemodynamic shear stress participates in maintaining vascular redox status. Elucidating flow-mediated endothelial metabolites enables us to discover metabolic biomarkers and therapeutic targets. We posited that flow-responsive vascular endothelial growth factor receptor (VEGFR)-protein kinase C isoform epsilon (PKCɛ)-6-phosphofructo-2-kinase/fructose-2,6-biphosphatase 3 (PFKFB3) signaling modulates glycolytic metabolites for vascular repair.ResultsBidirectional oscillatory flow (oscillatory shear stress [OSS]: 0.1 ± 3 dyne·cm-2 at 1 Hz) upregulated VEGFR-dependent PKCɛ expression to a greater degree than did unidirectional pulsatile flow (pulsatile shear stress [PSS]: 23 ± 8 dyne·cm-2 at 1 Hz) in human aortic endothelial cells (p

The efficient preparation of catalyst is an important topic for its industrial application. The Sn‐containing zeolite is one kind of important catalysts for many catalytic conversions of oxygenated chemicals. In this work, an efficient strategy for preparation of Sn‐MFI zeolite was developed, of which space‐time yield can reach 62.58 kg/m3⋅h, which is 120 times higher than that of typical hydrothermal route (0.53 kg/m3⋅h). Combining XRD, TEM, XPS, FT‐IR, 29Si NMR and other characterization methods, the framework tin sites were confirmed, and key role of ethylenediamine (EDA) for formation of which was revealed. Additionally, the framework tin sites content and catalytic activity of the Sn‐MFI prepared by this strategy is comparable to that of Sn‐MFI‐hy prepared by typical route in the conversion of dihydroxypropanone (DHA) to methyl lactate (ML), which gives ML yield of 80.64 % under optimized conditions. The proposed methodology can be extended to other types of Sn‐containing zeolite, which will certainly promote its industrial application. [ABSTRACT FROM AUTHOR]

Gluconobacter oxydans is a well-known acetic acid bacterium that has long been applied in the biotechnological industry. Its extraordinary capacity to oxidize a variety of sugars, polyols, and alcohols into acids, aldehydes, and ketones is advantageous for the production of valuable compounds. Relevant G. oxydans industrial applications are in the manufacture of L-ascorbic acid (vitamin C), miglitol, gluconic acid and its derivatives, and dihydroxyacetone. Increasing efforts on improving these processes have been made in the last few years, especially by applying metabolic engineering. Thereby, a series of genes have been targeted to construct powerful recombinant strains to be used in optimized fermentation. Furthermore, low-cost feedstocks, mostly agro-industrial wastes or byproducts, have been investigated, to reduce processing costs and improve the sustainability of G. oxydans bioprocess. Nonetheless, further research is required mainly to make these raw materials feasible at the industrial scale. The current shortage of suitable genetic tools for metabolic engineering modifications in G. oxydans is another challenge to be overcome. This paper aims to give an overview of the most relevant industrial G. oxydans processes and the current strategies developed for their improvement. [ABSTRACT FROM AUTHOR]

Catalytic valorization of raw glycerol derived from biodiesel into high-value chemicals has attracted great attention. Here, we report chemoenzymatic cascade reactions that convert glycerol to lactic acid and glycolic acid. In the enzymatic step, a coenzyme recycling system was developed to convert glycerol into 1,3-dihydroxyacetone (DHA) with a yield of 92.3% in potassium phosphate buffer (300 mM, pH 7.1) containing 100 mM glycerol, 2 mM NAD+, 242 U/mL glycerol dehydrogenase-GldA and NADH oxidase-SpNoxK184R at 30 °C. Subsequently, NaOH or NaClO2 catalyzes the formation of lactic acid and glycolic acid from DHA. The high yield of lactic acid (72.3%) and glycolic acid (78.2%) verify the benefit of the chemoenzymatic approaches. [ABSTRACT FROM AUTHOR]

Glycerol, the "co-product" in the biodiesel process, can be considered as a raw material to expand a biorefinery scheme. Selective reductions and oxidations and steam reforming of glycerol were studied to produce added-value chemicals and energetic compounds, and also to show a possible integration of processes into a biorefinery framework. Selective reductions of glycerol in gas phase produced: i) propylene glycol on Cu-Ce/Al 2 O 3 , reaching 99.8% conversion and 83.2% selectivity to propylene glycol; and ii) ethylene glycol on Ni/SiO 2 , achieving 100% conversion and 91% selectivity to ethylene glycol in the liquid fraction. These reduction reactions demand hydrogen, which can also be obtained by steam reforming of glycerol using Ni/Al 2 O 3 promoted by adding compounds as Ce, Co, Mg, and Zr; the steam reforming also produced carbon oxides and methane, being possible to use the syngas (hydrogen plus carbon monoxide) and methane as energetic compounds and carbon dioxide to carbonylation. Selective oxidations of glycerol in liquid phase produced: i) dihydroxyacetone on Pt/K-FER, being the first active and selective monometallic catalyst for this transformation, improving the catalytic behavior by using Pt-Bi/K-FER, reaching 75.9% conversion and 93.9% selectivity to dihydroxyacetone; and ii) lactic acid on Cu/Al 2 O 3 , obtaining 99.8% conversion and 86.5% selectivity to lactic acid. From the strong link with the productive sector, one pilot plant to produce 100 t/y of propylene glycol from glycerol but versatile to also obtain acetol and/or ethylene glycol is in the final building stage, and another one for reforming glycerol to produce the hydrogen demanded for those reduction processes was finished. Consequently, glycerol was converted to propylene glycol, ethylene glycol, hydrogen, dihydroxyacetone, lactic acid, syngas, carbon dioxide, and methane; therefore, the possible integration of the corresponding processes allows consider the co-product of biodiesel as a compound to expand a biorefinery scheme. [Display omitted] • Glycerol, the "co-product" of biodiesel, can be a raw material for expand a biorefinery. • Propylene glycol renewable is selectively produced in gas phase using Cu-Ce/Al 2 O 3. • Ethylene glycol is selectively produced by hydrogenolysis in gas phase on Ni/SiO 2. • Steam reforming at 700 °C produces the hydrogen needed to obtain the previous glycols. • Pt and Pt-Bi impregnated on potassium ferrierite allow obtain dihydroxyacetone. [ABSTRACT FROM AUTHOR]

Glycerol is an abundant byproduct of biodiesel production that has significant industrial value and can be converted into dihydroxyacetone (DHA). DHA is widely used for the production of various chemicals, pharmaceuticals, and food additives. Gluconobacter can convert glycerol to DHA through two different pathways, including membrane‐bound dehydrogenases with pyrroloquinoline quinone (PQQ) and NAD(P)+‐dependent enzymes. Previous work has indicated that membrane‐bound dehydrogenases are present in Gluconobacter oxydans and Gluconobacter frateurii, but the metabolic mechanism of Gluconobacter thailandicus's glycerol conversion is still not clear. Through in‐depth analysis of the G. thailandicus genome and annotation of its metabolic pathways, we revealed the existence of both PQQ and NAD(P)+‐dependent enzymes in G. thailandicus. In addition, this study provides important information related to the tricarboxylic acid cycle, glycerol dehydrogenase level, and phylogenetic relationships of this important species. [ABSTRACT FROM AUTHOR]

Abstract Background Klebsiella pneumoniae is a bacterium that can be used as producer for numerous chemicals. Glycerol can be catabolised by K. pneumoniae and dihydroxyacetone is an intermediate of this catabolism pathway. Here dihydroxyacetone and glycerol were produced from glucose by this bacterium based a redirected glycerol catabolism pathway. Results tpiA, encoding triosephosphate isomerase, was knocked out to block the further catabolism of dihydroxyacetone phosphate in the glycolysis. After overexpression of a Corynebacterium glutamicum dihydroxyacetone phosphate dephosphorylase (hdpA), the engineered strain produced remarkable levels of dihydroxyacetone (7.0 g/L) and glycerol (2.5 g/L) from glucose. Further increase in product formation were obtained by knocking out gapA encoding an iosenzyme of glyceraldehyde 3-phosphate dehydrogenase. There are two dihydroxyacetone kinases in K. pneumoniae. They were both disrupted to prevent an inefficient reaction cycle between dihydroxyacetone phosphate and dihydroxyacetone, and the resulting strains had a distinct improvement in dihydroxyacetone and glycerol production. pH 6.0 and low air supplement were identified as the optimal conditions for dihydroxyacetone and glycerol production by K, pneumoniae ΔtpiA-ΔDHAK-hdpA. In fed batch fermentation 23.9 g/L of dihydroxyacetone and 10.8 g/L of glycerol were produced after 91 h of cultivation, with the total conversion ratio of 0.97 mol/mol glucose. Conclusions This study provides a novel and highly efficient way of dihydroxyacetone and glycerol production from glucose.