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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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

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]

1,3-Dihydroxyacetone (DHA) is a three-carbon ketose with a simple structure and easy to dissolve in water. It has active chemical properties and is commonly used in the production of pharmaceutical intermediates chemical raw materials, food additives and other aspects. 1,3-Dihydroxyacetone is a high value-added product of the by-product glycerol in the production of biodiesel. The production of DHA by microbial fermentation technology or chemical catalytic oxidation is in line with the current national conditions for maximizing resource utilization in this country. This article introduces the separation and purification process such as alcohol precipitation-crystallization method, reaction-extraction method, adsorption separation, membrane separation, thin-film evaporation method and the current research progress. The advantages and disadvantages of these separation processes are analyzed and the future development prospects are prospected. [ABSTRACT FROM AUTHOR]

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]

• [BMIm][OAc] was applied in the synthesis of 1,2-diols and α-hydroxyketones. • Dihydroxyacetone derivatives were generated from the carbene/1,2-diol complex. • Benzaldehyde containing electron-rich groups promoted carbene regeneration. • The reaction mechanism and path were proposed through NMR and MS experiments. The α-hydroxyketones and 1,2-diols are versatile building blocks for the preparation of many natural and synthetic bioactive compounds. In this study, N-heterocyclic carbon (NHC) promoted coupling of several aldehydes with formaldehyde enabled the synthesis of 1,2-diols in moderate to high yields. The highly selective conversion of several aldehydes and formaldehyde into 1,2-diols and α-hydroxyketones was achieved in a one-pot two-step process via [BHMIm][OAc] as a key intermediate. In the first step, formaldehyde was quantitatively converted to [BHMIm][OAc] through the carbene addition. In the second step, 1,2-diol was produced through the intermediate-promoted aldol reaction. The results showed that benzaldehyde was capable to react with [BHMIm][OAc] efficiently, with a 54.1% yield of 1,2-diol after the 3-hour reaction at 85 °C. Among the tested benzaldehyde derivatives, the 4-nitrobenzaldehyde showed the highest yield of 1,2-diol (73.3%) under the optimized reaction conditions. Incorporation of an electron rich group on benzaldehyde promoted carbene regeneration. With 4-methoxybenzaldehyde as the substrate, the yield of α-hydroxyketone reached a maximum of 30.6%. Additionally, dihydroxyacetone derivatives were detected in the system. In situ NMR technique confirmed that it was generated from the further reaction of the carbene/1,2-diol complex with another aldehyde. Based on the results of NMR spectroscopy and mass spectrometry, a possible reaction pathway was also proposed. [Display omitted] [ABSTRACT FROM AUTHOR]

• Copper-mediated C 3 N 4 -BiVO 4 organic-inorganic hybrids were synthesized. • Production of 1O 2 was enhanced through energy transfer. • Production of O 2 − was enhanced through electron transfer. • Selectivity and yield of DHA was significantly enhanced. • DFT calculation has been utilized to explain the catalytic mechanism. Singlet oxygen (1O 2) is a kind of reactive oxygen species (ROS) with both oxidizability and selectivity. The construction of 1O 2 is the key to improve the selectivity of various organic reactions. In this study, Cu/C 3 N 4 -BiVO 4 (CCN-BVO) ternary system significantly improved the catalytic effect of selective oxidation of glycerol to prepare high value chemical dihydroxyacetone (DHA). At the same time, CCN-BVO also has a strong environmental catalytic effect, and the decomposition effect of liquid phase organic pollutants can reach more than 90 % within 2 h. The superior ROS production capacity of CCN-BVO, particularly its ability to produce 1O 2 , has been confirmed by electron spin resonance (ESR) and quenching experiments as the reason for its excellent catalytic effect. Electrochemical characterization and X-ray photoelectron spectroscopy (XPS) proved that Cu can be used as an intermediary to accelerate electron conduction, and can also effectively construct defects to improve oxygen absorption efficiency, thus effectively increasing ROS yield. This study also theoretically confirmed the reaction path of glycerol catalysis through DFT calculation, which provided a theoretical basis for the subsequent design of efficient catalytic materials. [ABSTRACT FROM AUTHOR]

[Display omitted] • System built with hollow fiber columns & perfusion culture technology. • Dynamic model established for ICSS system. • Regeneration processes extend cell lifetime. • DHA yield: 1237.8 g, up 485.0 %; Conversion rate: 97.7 %. Currently, the predominant method for the industrial production of 1,3-dihydroxyacetone (DHA) from glycerol involves fed-batch fermentation. However, previous research has revealed that in the biocatalytic synthesis of DHA from glycerol, when the DHA concentration exceeded 50 g·L−1, it significantly inhibited microbial growth and metabolism, posing a challenge in maintaining prolonged and efficient catalytic production of DHA. In this study, a new integrated continuous production and synchronous separation (ICSS) system was constructed using hollow fiber columns and perfusion culture technology. Additionally, a cell reactivation technique was implemented to extend the biocatalytic ability of cells. Compared with fed-batch fermentation, the ICSS system operated for 360 h, yielding a total DHA of 1237.8 ± 15.8 g. The glycerol conversion rate reached 97.7 %, with a productivity of 3.44 g·L−1·h−1, representing 485.0 % increase in DHA production. ICSS system exhibited strong operational characteristics and excellent performance, indicating significant potential for applications in industrial bioprocesses. [ABSTRACT FROM AUTHOR]

Exogenous exposures to the triose sugar dihydroxyacetone (DHA) occur from sunless tanning products and electronic cigarette aerosol. Once inhaled or absorbed, DHA enters cells, is converted to dihydroxyacetone phosphate (DHAP), and incorporated into several metabolic pathways. Cytotoxic effects of DHA vary across the cell types depending on the metabolic needs of the cells, and differences in the generation of reactive oxygen species (ROS), cell cycle arrest, and mitochondrial dysfunction have been reported. We have shown that cytotoxic doses of DHA induced metabolic imbalances in glycolysis and oxidative phosphorylation in liver and kidney cell models. Here, we examine the dose-dependent effects of DHA on the rat cardiomyocyte cell line, H9c2. Cells begin to experience cytotoxic effects at low millimolar doses, but an increase in cell survival was observed at 2 mM DHA. We confirmed that 2 mM DHA increased cell survival compared to the low cytotoxic 1 mM dose and investigated the metabolic differences between these two low DHA doses. Exposure to 1 mM DHA showed changes in the cell's fuel utilization, mitochondrial reactive oxygen species (ROS), and transient changes in the glycolysis and mitochondrial energetics, which normalized 24 h after exposure. The 2 mM dose induced robust changes in mitochondrial flux through acetyl CoA and elevated expression of fatty acid synthase. Distinct from the 1 mM dose, the 2 mM exposure increased mitochondrial ROS and NAD(P)H levels, and sustained changes in LDHA/LDHB and acetyl CoA-associated enzymes were observed. Although the cells were exposed to low cytotoxic (1 mM) and non-cytotoxic (2 mM) acute doses of DHA, significant changes in mitochondrial metabolic pathways occurred. Further, the proliferation increase at the acute 2 mM DHA dose suggests a metabolic adaption occurred with sustained consequences in survival and proliferation. With increased exogenous exposure to DHA through e-cigarette aerosol, this work suggests cell metabolic changes induced by acute or potentially chronic exposures could impact cell function and survival. [Display omitted] • Non-cytotoxic doses of DHA induce dose-dependent changes in mitochondrial metabolic pathways. • Increased cell proliferation occurs in H9c2 at 2 mM DHA. • Cytotoxic doses of DHA induce mitophagy and suppression of mitochondrial metabolic pathways. [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]

Stable isotopes at natural abundance are key tools to study physiological processes occurring outside the temporal scope of manipulation and monitoring experiments. Whole-molecule carbon isotope ratios (13C/12C) enable assessments of plant carbon uptake yet conceal information about carbon allocation. Here, we identify an intramolecular 13C/12C signal at tree-ring glucose C-5 and C-6 and develop experimentally testable theories on its origin. More specifically, we assess the potential of processes within C3 metabolism for signal introduction based (inter alia) on constraints on signal propagation posed by metabolic networks. We propose that the intramolecular signal reports carbon allocation into major metabolic pathways in actively photosynthesizing leaf cells including the anaplerotic, shikimate, and non-mevalonate pathway. We support our theoretical framework by linking it to previously reported whole-molecule 13C/12C increases in cellulose of ozone-treated Betula pendula and a highly significant relationship between the intramolecular signal and tropospheric ozone concentration. Our theory postulates a pronounced preference for leaf cytosolic triose-phosphate isomerase to catalyse the forward reaction in vivo (dihydroxyacetone phosphate to glyceraldehyde 3-phosphate). In conclusion, intramolecular 13C/12C analysis resolves information about carbon uptake and allocation enabling more comprehensive assessments of carbon metabolism than whole-molecule 13C/12C analysis. [ABSTRACT FROM AUTHOR]

Lactic acid is a renewable and versatile chemical for food, pharmaceuticals, cosmetics, and other chemicals. Lactic acid can be produced from biomass‐derived dihydroxyacetone. However, selective and recyclable water‐tolerant acid catalysts need to be developed for the specific production of lactic acid. Here we show that the MIL‐101(Al)−NH2 metal‐organic framework (MOF) is a water‐tolerant and selective solid Lewis acid catalyst for dihydroxyacetone isomerization to lactic acid. The Lewis acidic MIL‐101(Al)−NH2 catalyst promoted a high lactic acid selectivity of 91 % at 96 % dihydroxyacetone conversion at 120 °C in water. The reaction proceeded by temperature and/or MIL‐101(Al)−NH2 MOFs mediated dihydroxyacetone dehydration to pyruvaldehyde. Subsequently, the MIL‐101(Al)−NH2 facilitated rehydration of the pyruvaldehyde to lactic acid. The Lewis acidic MIL‐101(Al)−NH2 catalyst was stable and reusable four times without any decrease in catalytic performance. [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]

Transition-metal silicates are recognized as effective solid acid catalysts to produce value-added compounds from bio-based platform chemicals. One crucial feature in such catalytic transformations is the isomorphic substitution of transition metal into the tetrahedral coordination environment of SiO 2 matrices. This substitution generates the acidic sites which represent the catalytically active sites. Herein, the preparation of hafnium-doped mesoporous SiO 2 (hafnosilicates) is disclosed, and these materials are explored as catalysts for the efficient conversion of dihydroxyacetone (DHA) to ethyl lactate (EL). The one-step catalyst preparation is based on the aerosol-assisted sol-gel (AASG) process and leads to spherical mesoporous silicates with a homogeneous insertion of isolated Hf – as single sites into the SiO 2 matrix, as indicated by XPS. These sites display high Lewis acidity (as evidenced by Pyridine-IR) and this translates into good catalytic performance. Moreover, pH adjustment via the controlled addition of triethanolamine before the aerosol process is shown as a practical way to improve the textural properties, the degree of Hf insertion into the SiO 2 matrix (Lewis acidity), and therefore the catalytic activity. Under optimized reaction conditions (5 mL of 0.4 M DHA, 140 °C, 6 h, 200 mg of catalyst), complete conversion of DHA to EL was observed with a yield higher than 45%. [Display omitted] • Mesoporous hafnosilicate catalysts prepared in one step via an aerosol-assisted sol-gel process. • pH adjustment strategy greatly enhanced the degree of Hf insertion resulting in higher Lewis acidity. • Ethyl lactate yield was greatly improved by the amount of Lewis acidity in the hafnosilicates. • Hafnosilicates can be reused in several cycles with high stability and no leaching of active sites. [ABSTRACT FROM AUTHOR]

• Asymmetric oxygen vacancy was caused by Ce/Cu co-modification. • Production of 1O 2 was enhanced through energy transfer. • Production of ·O 2 − was enhanced through electron transfer. • Selectivity and yield of DHA was significantly enhanced. • DFT calculation has been utilized to explain the catalytic mechanism. The low selectivity and conversion rate of dihydroxyacetone (DHA) by glycerol oxidation over catalysts due to their poor reactive oxygen species (ROS) regulation, which still seriously limits the practical application. Engineering of ROS, especially singlet oxygen (1O 2), by constructing oxygen vacancies (OVs) can tune surface/bulk electronic structure and improve surface active sites of catalytic oxidation with desired selectivity and reactivity. Herein, we report the preparation of DHA by photothermal catalysis (PTC) of glycerol over Cu/Ce-BiVO 4 ternary system with unique Ce nanoisland structure on the surface of BiVO 4 substrate for effectively anchoring Cu. The forming Ce-O-Cu asymmetric oxygen vacancies can both promote the electron transfer to form superoxide anion (·O 2 −) and also improve the efficiency of energy transfer to generate 1O 2. Furthermore, the synergistic Ce and Cu bimetal active sites can regulate the microelectron structure of Ce3+/Ce4+ and Cu0/Cu+redox centers, leading an outstanding yield of 41.1% and a boosting selectivity reached to 59.7%.·O 2 − can enhance the conversion of glycerol oxidation, while 1O 2 can boost the selectivity to directionally form DHA. The synergistic effect of 1O 2 and ·O 2 − is the key to improve catalytic efficiency. First-principles calculations indicate that the most reasonable reaction pathway for 1O 2 production is O 2 →Cu/Ce-BVO→1O 2. This study explores the relationship between asymmetric oxygen vacancy and singlet oxygen production, and provides a basis for designing new high-performance catalysts. In this study, Ce-O-Cu asymmetric oxygen vacancy was constructed by Ce/Cu co-modification. The existence of asymmetric oxygen vacancy can generate singlet oxygen (1O 2) through energy transfer and superoxide anion (·O 2 −) through electron transfer. Under the synergistic action of 1O 2 and ·O 2 −, the selectivity and yield of glycerol (GLY) secondary hydroxyl oxidation to dihydroxyacetone (DHA) can be effectively improved. [Display omitted] [ABSTRACT FROM AUTHOR]

Selective oxidation of glycerol to dihydroxyacetone (DHA) is a promising pathway for glycerol utilization. In order to fabricate a highly stable supported Au catalyst for the reaction, a series of CuO-ZnO mixed oxides derived from different minerals were synthesized. Then, the Au/CuO-ZnO catalysts were prepared by the deposition-precipitation. High yield of DHA (70%) and conversion of glycerol (76%) were obtained over the rosasite-derived Au/CuO-ZnO catalyst. While over the aurichalcite-derived Au/CuO-ZnO catalyst, the yield of DHA was only 20%. By means of XRD, H 2 -TPR, TEM, XPS, CO 2 -TPD characterization, it was found that the higher yield of DHA was attributed to the stronger interaction between CuO and ZnO, higher dispersion of Au species, higher content of Au0 and proper amount of surface basic sites. The rosasite-derived Au/CuO-ZnO catalyst also showed good stability and no obvious decrease in reactivity and DHA selectivity could be seen after five recycles. The stable structure of the support not only enhanced the interaction between CuO-ZnO that stabilized the support itself, but also improved the interaction between Au and the support, further stabilizing the particle size and chemical valence of Au. [Display omitted] • Au catalysts supported on CuO-ZnO derived from mineral were employed for glycerol oxidation for the first time. • Highest yield of DHA and conversion of glycerol were obtained over rosasite-derived CuO-ZnO supported Au catalyst. • The rosasite-derived CuO-ZnO supported Au catalyst also showed good stability. • The special mineral structure improved the stability of the mixed oxide catalysts. [ABSTRACT FROM AUTHOR]

Summary: Most microorganisms can metabolize glycerol when external electron acceptors are available (i.e. under respiratory conditions). However, few can do so under fermentative conditions owing to the unique redox constraints imposed by the high degree of reduction of glycerol. Here, we utilize in silico analysis combined with in vivo genetic and biochemical approaches to investigate the fermentative metabolism of glycerol in Escherichia coli. We found that E. coli can achieve redox balance at alkaline pH by reducing protons to H2, complementing the previously reported role of 1,2‐propanediol synthesis under acidic conditions. In this new redox balancing mode, H2 evolution is coupled to a respiratory glycerol dissimilation pathway composed of glycerol kinase (GK) and glycerol‐3‐phosphate (G3P) dehydrogenase (G3PDH). GK activates glycerol to G3P, which is further oxidized by G3PDH to generate reduced quinones that drive hydrogenase‐dependent H2 evolution. Despite the importance of the GK‐G3PDH route under alkaline conditions, we found that the NADH‐generating glycerol dissimilation pathway via glycerol dehydrogenase (GldA) and phosphoenolpyruvate (PEP)‐dependent dihydroxyacetone kinase (DHAK) was essential under both alkaline and acidic conditions. We assessed system‐wide metabolic impacts of the constraints imposed by the PEP dependency of the GldA‐DHAK route. This included the identification of enzymes and pathways that were not previously known to be involved in glycerol metabolisms such as PEP carboxykinase, PEP synthetase, multiple fructose‐1,6‐bisphosphatases and the fructose phosphate bypass. [ABSTRACT FROM AUTHOR]

This study report for the first time an earth-abundant manganese oxide (MnO 2) was used for electrocatalytic glycerol oxidation with a satisfactory yield and high selectivity under mild pH media. [Display omitted] • First report of MnO 2 catalyst for electrooxidation of glycerol. • High selectivity toward DHA (∼46%) under high current density (∼6 mAcm−2) could be achieved. • Reaction pathway of glycerol electrooxidation was proposed based on HPLC, Raman spectroscopy, and electrochemical studies. • High DHA selectivity at high potential due to partial transformation of α-MnO 2 to δ-MnO 2. In this study, earth-abundant manganese oxide (MnO 2) was used as a catalyst for the electrocatalytic glycerol oxidation with a satisfactory yield and high selectivity under mild pH media; that is, the high current density of 6.0 mA cm−2 and selectivity of ca. 46% for dihydroxyacetone (DHA). MnO 2 also exhibited reasonable durability without considerable changes for 3 h. More importantly, by combination of operando Raman and electrochemical studies, a tentative reaction pathway was also proposed. It is found that high selectivity of formic acid at low potential was due to predominant coverage of α-MnO 2 on catalyst surface. Meanwhile, at high applied potential, partial transformation of α-MnO 2 to δ-MnO 2 causes decreasing C-C bond cleavage, leading to high DHA selectivity. The results of this work not only demonstrate that MnO 2 holds promise as an efficient electrocatalyst for selectively producing DHA but also provides realistic details on electrochemically generated species under working condition. [ABSTRACT FROM AUTHOR]

Klebsiella pneumoniae is an important microorganism and is used as a cell factory for many chemicals production. When glycerol was used as the carbon source, 1,3-propanediol was the main catabolite of this bacterium. K. pneumoniae ΔtpiA lost the activity of triosephosphate isomerase and prevented glycerol catabolism through the glycolysis pathway. But this strain still utilized glycerol, and 1,2-propanediol became the main catabolite. Key enzymes of 1,2-propanediol synthesis from glycerol were investigated in detail. dhaD and gldA encoded glycerol dehydrogenases were both responsible for the conversion of glycerol to dihydroxyacetone, but overexpression of the two enzymes resulted in a decrease of 1,2-propanediol production. There are two dihydroxyacetone kinases (I and II), but the dihydroxyacetone kinase I had no contribution to dihydroxyacetone phosphate formation. Dihydroxyacetone phosphate was converted to methylglyoxal, and methylglyoxal was then reduced to lactaldehyde or hydroxyacetone and further reduced to form 1,2-propanediol. Individual overexpression of mgsA, yqhD, and fucO resulted in increased production of 1,2-propanediol, but only the combined expression of mgsA and yqhD showed a positive effect on 1,2-propanediol production. The process parameters for 1,2-propanediol production by Kp ΔtpiA-mgsA-yqhD were optimized, with pH 7.0 and agitation rate of 350 rpm found to be optimal. In the fed-batch fermentation, 9.3 g/L of 1,2-propanediol was produced after 144 h of cultivation, and the substrate conversion ratio was 0.2 g/g. This study provides an efficient way of 1,2-propanediol production from glycerol via an endogenous pathway of K. pneumoniae. Key points • 1,2-Propanediol was synthesis from glycerol by a tpiA knocked out K. pneumoniae • Overexpression of mgsA, yqhD, or fucO promote 1,2-propanediol production • 9.3 g/L of 1,2-propanediol was produced in fed-batch fermentation [ABSTRACT FROM AUTHOR]

Summary: Current models of floral nectar production do not include a contribution from photosynthesis by green nectary tissue, even though many species have green nectaries. Mānuka (Leptospermum scoparium) floral nectaries are green, and in addition to sugars, their nectar contains dihydroxyacetone (DHA), the precursor of the antimicrobial agent in the honey. We investigated causes of variation in mānuka floral nectar production, particularly the effect of light incident on the nectary.Flower gas exchange, chlorophyll fluorescence, and the effects on nectar of age, temperature, light, sucrose, 3‐(3,4‐dichlorophenyl)‐1,1‐dimethylurea (DCMU), pyridoxal phosphate, and 13CO2, were measured for attached and excised flowers.Flower age affected all nectar traits, whilst temperature affected total nectar sugar only. Increased light reduced floral CO2 efflux, increased nectar sugar production, and affected the ratio of DHA to other nectar sugars. DCMU, an inhibitor of photosystem II, reduced nectar sugar production. Pyridoxal phosphate, an inhibitor of the chloroplast envelope triose phosphate transporter, reduced nectar DHA content. Incubation of excised flowers with 13CO2 in the light resulted in enrichment of nectar sugars, including DHA.Photosynthesis within green nectaries contributes to nectar sugars and influences nectar composition. Mānuka nectar DHA arises from pools of triose phosphate that are modulated by nectary photosynthesis. [ABSTRACT FROM AUTHOR]

In this work, several immobilization strategies for Gluconobacter oxydans NBRC 14819 (Gox) were tested in the bioconversion of crude glycerol to dihydroxyacetone (DHA). Agar, agarose and polyacrylamide were evaluated as immobilization matrixes. Glutaraldehyde crosslinked versions of the agar and agarose preparations were also tested. Agar immobilized Gox proved to be the best heterogeneous biocatalyst in the bioconversion of crude glycerol reaching a quantitative production of 50 g/L glycerol into DHA solely in water. Immobilization allowed reutilization for at least eight cycles, reaching four times more DHA than the amount obtained by a single batch of free cells which cannot be reutilized. An increase in scale of 34 times had no impact on DHA productivity. The results obtained herein constitute a contribution to the microbiological production of DHA as they not only attain unprecedented productivities for the reaction with immobilized biocatalysts but also proved that it is feasible to do it in a clean background of solely water that alleviates the cost of downstream processing. [Display omitted] • Gluconobacter oxydans NBRC 14819 (Gox) was immobilized in agar, agarose and polyacrylamide. • Gox immobilized in agar was best bioconverting crude glycerol to dihydroxyacetone. • Productivities reached 0.85 g/Lh in water and the Gox preparation could be reused up to 8 times. • DHA productivity was maintained as the process was scaled up 34 times. [ABSTRACT FROM AUTHOR]

Cooling crystallization of 1, 3-dihydroxyacetone (DHA) in 90% ethanol aqueous solution were investigated, and the effects of glycerol (GLY), glyceraldehyde (GL YD) and glyceric acid (GLYA) as impurities on the final solid product purity, yield, habit and particle size were comparatively studied. The results show that glycerol has a strong influence on the purity of DHA product, while GLYD and GLYA have almost no impact. The yield of DHA product increases with the increase of GLY and GLYA contents, but decreases first and then increases with the increase of GLYD content. Moreover, the addition of impurities leads to irregular morphology of DHA crystal, and the particle size distribution of crystalline products is bimodal. [ABSTRACT FROM AUTHOR]

Realizing a sustainable future requires intensifying the waste stream conversion, such as converting the greenhouse gas carbon dioxide into value-added products. In this paper, we focus on utilizing formaldehyde as a C1 carbon source for enzymatic C–C bond formation. Formaldehyde can be sustainably derived from other C1 feedstocks, and in this work, we designed a synthetic enzyme cascade for producing the functional C4 sugar erythrulose. This involved tailoring the enzyme formolase, which was optimized for fusing formaldehyde, from a three-carbon producer (dihydroxyacetone) to sets of variants with enhanced two-carbon (glycolaldehyde) or four-carbon (erythrulose) activity. To achieve this, a high-throughput combinatorial screening was developed, and every single variant was evaluated in terms of glycolaldehyde, dihydroxyacetone and erythrulose activity. By applying the two most promising variants in an enzyme cascade, we were able to show for the first time production of ERY starting from a C1 carbon source. In addition, we demonstrated that one of our tailored formolase variants was able to convert 25.0 g L−1 glycolaldehyde to 24.6 g L−1 erythrulose (98% theoretical yield) in a fully atom-economic biocatalytic process. This represents the highest achieved in vitro concentration of erythrulose to date. [ABSTRACT FROM AUTHOR]

Renewable-driven CO2 recycling plants (CO2RPs) to produce chemicals have a certain role to play in the decarbonization of the economy. In recent years, significant progress has been made in the decarbonization of chemicals such as formate/formic acid (HCOO−/HCOOH) by CO2 electrochemical reduction (CO2ER). The traditional approach consists of the cathodic CO2ER coupled to the anodic oxygen evolution reaction (OER). Current trends consist of alternative anodic processes, such as glycerol (GLY) electro-oxidation (EOG), as a powerful alternative to the OER because it can noticeably lower the cell voltage. Also, this recent alternative leads to the formation of products in the anode with more economic value than O2, for example, the fine chemical dihydroxyacetone (DHA). Until now factors other than just the energy savings in the ER cell have been neglected. But these factors, such as the anodic market size, the downstream separation energy demand, etc., have to be contemplated in the whole decarbonization picture. In the present study, we analyze the environmental and economic benefits of the integrated production of HCOO− and DHA by a renewable-driven CO2RP in which the traditional OER is substituted by the EOG alternative. Life Cycle Thinking was used to support the decision-making. HCOO− and DHA fossil routes as well as the traditional decarbonization OER scheme (that decarbonized the amount of HCOO−) were used for benchmarking. The integrated production in the proposed CO2RP is highly limited by the small market size of DHA compared to that of HCOO− and also by the high energy requirements in the DHA purification step. Anodic DHA concentration over 1.5 wt% is compulsory in short–mid-term developments to achieve a positive decarbonization scenario wherein the integrated production of DHA and HCOO− is compared with the traditional route. A noticeable reduction in the market price of DHA would be possible with appropriate anode developments. In addition, we evaluate the influence of the renewable electricity market forecast in the economic figures of DHA and HCOO− produced by the co-electrolysis technology. [ABSTRACT FROM AUTHOR]

The world's biodiesel increasing production is leading to the accumulation of its main by-product, crude glycerol, with almost no economic value, which valorization is crucial to increase biodiesel production sustainability and competitiveness. Glycerol is a potential platform chemical, with several valorization routes identified. Among them, selective catalytic aerobic oxidation is an attractive and sustainable solution, as high added value products ensure the process robustness against raw material price fluctuations. When glycerol's secondary hydroxyl group is selectively oxidized, dihydroxyacetone (DHA) is obtained. DHA is a high added value compound, used in cosmetics as the active compound in sunless skin tanning lotions, and its current industrial production by bio-fermentation is not satisfactory; therefore a more efficient production process is needed to overcome the market deficit. The state-of-the-art of DHA production by glycerol aerobic catalytic oxidation in the liquid phase with water as solvent was reviewed and, although it is still in the lab-scale phase, some routes to reach a robust commercial application were already suggested. For DHA production, catalysts should be active under base free conditions, in order to achieve high DHA selectivity. Promoted Pt nanoparticles, as Pt-Bi and Pt-Sb supported in carbon and mesoporous materials, and Au nanoparticles, supported late transition metal oxides as Au/CuO and Au/ZnO, are among the most promising catalysts for high DHA yield processes. For a better understanding of the main variables associated with this process, the effect of catalyst support, particle size, preparation and activation methods, and catalyst deactivation problems were analyzed. In addition, the reaction conditions effect in catalyst performance, including the presence of crude glycerol impurities was considered. Finally, the main studies regarding DHA continuous flow production were reviewed, identifying the major obstacles to overcome, so that commercial DHA production processes through glycerol aerobic catalytic oxidation can finally be implemented. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Summary: More than 2 million tons of glycerol are produced during industrial processes each year and, therefore, glycerol is an inexpensive feedstock to produce biocommodities by bacterial fermentation. Acetogenic bacteria are interesting production platforms and there have been few reports in the literature on glycerol utilization by this ecophysiologically important group of strictly anaerobic bacteria. Here, we show that the model acetogen Acetobacterium woodii DSM1030 is able to grow on glycerol, but contrary to expectations, only for 2–3 transfers. Transcriptome analysis revealed the expression of the pdu operon encoding a propanediol dehydratase along with genes encoding bacterial microcompartments. Deletion of pduAB led to a stable growth of A. woodii on glycerol, consistent with the hypothesis that the propanediol dehydratase also acts on glycerol leading to a toxic end‐product. Glycerol is oxidized to acetate and the reducing equivalents are reoxidized by reducing CO2 in the Wood–Ljungdahl pathway, leading to an additional acetate. The possible oxidation product of glycerol, dihydroxyacetone (DHA), also served as carbon and energy source for A. woodii and growth was stably maintained on that compound. DHA oxidation was also coupled to CO2 reduction. Based on transcriptome data and enzymatic analysis we present the first metabolic and bioenergetic schemes for glycerol and DHA utilization in A. woodii. [ABSTRACT FROM AUTHOR]

Glycerol (Gly) can be dissimilated by two pathways in bacteria. Either this sugar alcohol is first oxidized to dihydroxyacetone (DHA) and then phosphorylated or it is first phosphorylated to glycerol-3-phosphate (GlyP) followed by oxidation. Oxidation of GlyP can be achieved by NAD-dependent dehydrogenases or by a GlyP oxidase. In both cases, dihydroxyacetone phosphate is the product. Genomic analysis showed that Enterococcus faecium harbors numerous genes annotated to encode activities for the two pathways. However, our physiological analyses of growth on glycerol showed that dissimilation is limited to aerobic conditions and that despite the presence of genes encoding presumed GlyP dehydrogenases, the GlyP oxidase is essential in this process. Although E. faecium contains an operon encoding the phosphotransfer protein DhaM and DHA kinase, which are required for DHA phosphorylation, it is unable to grow on DHA. This operon is highly expressed in stationary phase but its physiological role remains unknown. Finally, data obtained from sequencing of a transposon mutant bank of E. faecium grown on BHI revealed that the GlyP dehydrogenases and a major intrinsic family protein have important but hitherto unknown physiological functions. [ABSTRACT FROM AUTHOR]

Glycogenolysis and gluconeogenesis are sensitive to nutritional state and their balances are disrupted in the liver by different pathological states. The regulation of the balance between glucose production and synthesis of glycogen continues to be a matter of investigation because of its implications in diseases and its value for therapeutics. We used the gluconeogenic precursor dihydroxyacetone (DHA) to study glycogen synthesis in isolated rat hepatocytes under gluconeogenic conditions. We used a glycogen phosphorylase (GP) inhibitor, 2-deoxy-2-fluoro-α-D-glucopyranosyl fluoride (F2Glc) to prevented GP from breaking up glycogen into glucose subunits and had a pool of glucose in the medium. Therefore, we evaluated the contribution of DHA as a unique source of carbohydrates on glycogen metabolism. We showed that DHA increased G6P levels that induced both GS activation and its translocation and, thus, an increment of glycogen deposition in a similar way as glucose did. [ABSTRACT FROM AUTHOR]

Among many theories on the life's origins, the regions between star systems in a galaxy are hypothesized to provide prebiotic material on Earth. Simple sugars, including glycolaldehyde, are confirmed to exist in interstellar medium (ISM) and can be intermediates in the formose reaction to form dihydroxyacetone (DHA). In the studied segment of the formose reaction, hydroxy carbene is sequentially added to formaldehyde, forming glycolaldehyde (hydroxyacetaldehyde) after the first addition and glycerone in the second addition. The proposed theoretical mechanism was validated through quantum chemical calculations. An exothermic and exergonic pathway favourable in ISM conditions was found, giving a possible explanation for glycerone formation. The products in question participate in biological processes like energy production, the phosphorylated form of glycerone (DHA-P) participates in glycolysis, and energy storage while glycerone is the source of the glycerine backbone in lipids. The studied reaction is a segment of the formose reaction and further polymerization can lead to pentose and hexose, which participate in the formation of RNA and DNA. Hence, this research explores the exogenous production and delivery of prebiotic material to Earth, building up to the conditions allowing the formation of rudimentary lifeforms. [ABSTRACT FROM AUTHOR]

We report the synthesis of a series of symmetrical lipids composed of dihydroxyacetone and even‑carbon fatty acids (eight to sixteen carbons), both components of the human metabolome, and characterize their formulation into porous microparticles through spontaneous emulsification without the use of additional porogens. Lipid hydrolysis products were identified by 1H NMR to validate lipid degradation into the parent metabolic synthons. Microparticle architecture, as determined by scanning electron microscopy, was lipid-length dependent, with shorter alkyl chains forming tight structures and longer alkyl chains forming larger pores with plate-like lipid architectures. In all cases, the lipids formed organized patterns, not irregular shapes. As a demonstration of the potential use of these solid lipid-based microparticles, the release kinetics of a model drug (piroxicam) was quantified showing that release was more greatly influenced by microparticle porosity, and hence surface area, than by hydrophobicity of the lipids. Unlabelled Image [ABSTRACT FROM AUTHOR]

Dihydroxyacetone (DHA), a chemical suntan agent, is produced by the regiospecific oxidation of glycerol with Gluconobacter thailandicus NBRC3255. However, this microorganism consumes DHA produced in the culture medium. Here, we attempted to understand the pathway for DHA metabolism in NBRC3255 to minimize DHA degradation. The two gene products, NBRC3255_2003 (DhaK) and NBRC3255_3084 (DerK), have been annotated as DHA kinases in the NBRC 3255 draft genome. Because the double deletion derivative for dhaK and derK showed ATP-dependent DHA kinase activity similar to that of the wild type, we attempted to purify DHA kinase from ∆dhaK ∆derK cells to identify the gene for DHA kinase. The identified gene was NBRC3255_0651, of which the product was annotated as glycerol kinase (GlpK). Mutant strains with several combinations of deletions for the dhaK, derK, and glpK genes were constructed. The single deletion strain ∆glpK showed approximately 10% of wild-type activity and grew slower on glycerol than the wild type. The double deletion strain ∆derK ∆glpK and the triple deletion strain ∆dhaK ∆derK ∆glpK showed DHA kinase activity less than a detection limit and did not grow on glycerol. In addition, although ΔderK ΔglpK consumed a small amount of DHA in the late phase of growth, ∆dhaK ΔderK ΔglpK did not show DHA consumption on glucose–glycerol medium. The transformants of the ∆dhaK ΔderK ΔglpK strain that expresses one of the genes from plasmids showed DHA kinase activity. We concluded that all three DHA kinases, DhaK, DerK, and GlpK, are involved in DHA metabolism of G. thailandicus. Key points: • Dihydroxyacetone (DHA) is produced but degraded by Gluconobacter thailandicus. • Phosphorylation rather than reduction is the first committed step in DHA metabolism. • Three kinases are involved in DHA metabolism with the different properties. [ABSTRACT FROM AUTHOR]