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Frontiers in Chemistry 2022Nanotube/nanowire-structured TiO was formed on the Ti surface by an anodic oxidation method performed at different potential values (50 or 60 V) and for different times...
Nanotube/nanowire-structured TiO was formed on the Ti surface by an anodic oxidation method performed at different potential values (50 or 60 V) and for different times (3 or 5 h). The TiO photocatalysts were taken in powder form using the ultrasonic treatment from the Ti electrodes, calcined at different temperatures, and characterized by XRD and SEM techniques, and BET surface area analyses. Both the crystallinity and the size of the primary TiO particles increased by increasing the heat treatment temperature. While all the photocatalysts heat treated up to 500°C were only in the anatase phase, the particles heat-treated at 700°C consisted of both anatase and rutile phases. The BET specific surface area of the samples decreased drastically after heat treatment of 700°C because of partial sinterization. SEM analyses indicated that the prepared materials were structured in both nanotubes and nanowires. They were tested as photocatalysts for the selective oxidation of glycerol and 3-pyridinemethanol under UVA irradiation in water at room temperature and ambient pressure. Glyceraldehyde, 1,3-dihydroxyacetone, and formic acid were determined as products in glycerol oxidation, while the products of 3-pyridinemethanol oxidation were 3-pyridinemethanal and vitamin B. Non-nanotube/nanowire-structured commercial (Degussa P25 and Merck TiO) photocatalysts were used for the sake of comparison. Low selectivity values towards the products obtained by partial oxidation were determined for glycerol. On the contrary, higher selectivity values towards the products were obtained (total 3-pyridinemethanal and vitamin B selectivity up to ca. 90%) for the photocatalytic oxidation of 3-pyridinemethanol. TiO photocatalysts must be highly crystalline (calcined at 700°C) for effective oxidation of glycerol, while for the selective oxidation of 3-pyridinemethanol it was not necessary to obtain a high crystallinity, and the optimal heat treatment temperature was 250°C. Glycerol and its oxidation products could more easily desorb from highly crystalline and less hydroxylated surfaces, which would justifies their higher activity. The prepared photocatalysts showed lower activity than Degussa P25, but a greater selectivity towards the products found.
PubMed: 35646812
DOI: 10.3389/fchem.2022.856947 -
Sheng Wu Gong Cheng Xue Bao = Chinese... Jul 2018Xylulose as a metabolic intermediate is the precursor of rare sugars, and its unique pattern of biological activity plays an important role in the fields of food,...
Xylulose as a metabolic intermediate is the precursor of rare sugars, and its unique pattern of biological activity plays an important role in the fields of food, health, medicine and so on. The aim of this study was to design a new pathway for xylulose synthesis from formaldehyde, which is one of the most simple and basic organic substrate. The pathway was comprised of 3 steps: (1) formaldehyde was converted to glycolaldehyde by benzoylformate decarboxylase mutant BFD-M3 (from Pseudomonas putida); (2) formaldehyde and glycolaldehyde were converted to dihydroxyacetone by BFD-M3 as well; (3) glycolaldehyde and dihydroxyacetone were converted to xylulose by transaldolase mutant TalB-F178Y (from Escherichia coli). By adding formaldehyde (5 g/L), BFD-M3 and TalB-F178Y in one pot, xylulose was produced at a conversion rate of 0.4%. Through optimizing the concentration of formaldehyde, the conversion rate of xylulose was increased to 4.6% (20 g/L formaldehyde), which is 11.5 folds higher than the initial value. In order to further improve the xylulose conversion rate, we employed Scaffold Self-Assembly technique to co-immobilize BFD-M3 and TalB-F178Y. Finally, the xylulose conversion rate reached 14.02%. This study provides a new scheme for the biosynthesis of rare sugars.
Topics: Bacterial Proteins; Carboxy-Lyases; Enzymes, Immobilized; Escherichia coli; Formaldehyde; Industrial Microbiology; Pseudomonas putida; Xylulose
PubMed: 30058311
DOI: 10.13345/j.cjb.170466 -
Toxins Nov 2022The traditional Chinese herbal medicine Turcz. () has been widely adopted to treat nausea, diabetes, siriasis, and poor appetite. However, contains multiple...
The traditional Chinese herbal medicine Turcz. () has been widely adopted to treat nausea, diabetes, siriasis, and poor appetite. However, contains multiple pyrrolizidine alkaloids (PAs). This study aimed to investigate the hepatotoxicity of total alkaloids in (EFTAs) and identify the toxic mechanisms of EFTAs on hepatocytes. Liquid chromatography with a tandem mass spectrometry assay with reference standards indicated that EFTAs mainly consisted of eight PAs whose content accounted for 92.38% of EFTAs. EFTAs markedly decreased mouse body and liver weights and increased the contents of AST and ALT. The histopathological assays demonstrated that, after exposition to EFTAs, the structures of hepatocytes were damaged and the fibrosis and apoptosis in hepatocytes were accelerated. Moreover, EFTAs increased the serum level of inflammatory cytokines and aggravated circulating oxidative stress. A combination of hepatic proteomics and metabolomics was used to investigate the toxic mechanisms of EFTAs. The study revealed that EFTAs seriously disrupted glycerophospholipid metabolism by upregulating the contents of lysophosphatidylglycerol acyltransferase 1 and phosphatidylinositol and downregulating the contents of choline/ethanolamine kinase beta, choline-ethanolamine phosphotransferase 1, phospholipase D4, 1-acylglycerophosphocholine, phosphatidylcholine, and dihydroxyacetone phosphate in the liver, resulting in detrimental inflammation, fibrosis, and apoptosis. This study revealed that EFTAs induced severe hepatotoxicity by disrupting glycerophospholipid metabolism.
Topics: Mice; Animals; Eupatorium; Proteomics; Pyrrolizidine Alkaloids; Alkaloids; Metabolomics; Chemical and Drug Induced Liver Injury; Fibrosis; Glycerophospholipids; Choline
PubMed: 36356015
DOI: 10.3390/toxins14110765 -
Applied and Environmental Microbiology Nov 2021Glycerol is an eco-friendly solvent that enhances plant biomass decomposition via glycerolysis in many pretreatment methods. Nonetheless, inefficient conversion of...
Glycerol is an eco-friendly solvent that enhances plant biomass decomposition via glycerolysis in many pretreatment methods. Nonetheless, inefficient conversion of glycerol to ethanol by natural Saccharomyces cerevisiae limits its use in these processes. In this study, we have developed an efficient glycerol-converting yeast strain by genetically modifying the oxidation of cytosolic NAD (NADH) by an O-dependent dynamic shuttle and abolishing both glycerol phosphorylation and biosynthesis in S. cerevisiae strain D452-2, as well as by vigorous expression of whole genes in the dihydroxyacetone (DHA) pathway (Candida utilis glycerol facilitator, Ogataea polymorpha glycerol dehydrogenase, endogenous dihydroxyacetone kinase, and triosephosphate isomerase). The engineered strain showed conversion efficiencies (CE) up to 0.49 g ethanol/g glycerol (98% of theoretical CE), with a production rate of >1 g liter h when glycerol was supplemented in a single fed-batch fermentation in a rich medium. Furthermore, the engineered strain converted a mixture of glycerol and glucose into bioethanol (>86 g/liter) with 92.8% CE. To the best of our knowledge, this is the highest reported titer of bioethanol produced from glycerol and glucose. Notably, we developed a glycerol-utilizing transformant from a parent strain which cannot utilize glycerol as a sole carbon source. The developed strain converted glycerol to ethanol with a productivity of 0.44 g liter h on minimal medium under semiaerobic conditions. Our findings will promote the utilization of glycerol in eco-friendly biorefineries and integrate bioethanol and plant oil industries. With the development of efficient lignocellulosic biorefineries, glycerol has attracted attention as an eco-friendly biomass-derived solvent that can enhance the dissociation of lignin and cell wall polysaccharides during the pretreatment process. Coconversion of glycerol with the sugars released from biomass after glycerolysis increases the resources for ethanol production and lowers the burden of component separation. However, low conversion efficiency from glycerol and sugars limits the industrial application of this process. Therefore, the generation of an efficient glycerol-fermenting yeast will promote the applicability of integrated biorefineries. Hence, metabolic flux control in yeast grown on glycerol will lead to the generation of cell factories that produce chemicals, which will boost biodiesel and bioethanol industries. Additionally, the use of glycerol-fermenting yeast will reduce global warming and generation of agricultural waste, leading to the establishment of a sustainable society.
Topics: Ethanol; Glucose; Glycerol; Industrial Microbiology; Microorganisms, Genetically-Modified; Saccharomyces cerevisiae; Solvents; Sugars
PubMed: 34524902
DOI: 10.1128/AEM.00268-21 -
Arhiv Za Higijenu Rada I Toksikologiju Jun 2018Aluminium phosphide (AlP), a very toxic pesticide also known as the rice tablet, releases phosphine gas upon contact with water, moisture, or gastric acid. Its mortality...
Aluminium phosphide (AlP), a very toxic pesticide also known as the rice tablet, releases phosphine gas upon contact with water, moisture, or gastric acid. Its mortality rate in humans is 70-100 % due to cardiogenic shock and refractory hypotension. Dihydroxyacetone (DHA) is a simple ketonic carbohydrate, mainly used for sunless skin tanning. It also plays a beneficial role in the treatment of hypotension and cardiogenic shock by restoring blood volume and cellular respiration. The aim of this study was to investigate the its effect on the haemodynamics and electrocardiogram (ECG) in male rats poisoned with AlP. The animals were divided into the following groups: control (received 1 mL corn oil, orally), AlP (received 15 mg kg-1 AlP solved in corn oil, orally), AlP plus DHA (treated with 50 mg kg-1 of DHA 30 min after receiving AlP), and AlP plus N-acetyl cysteine (NAC) (treated with 200 mg kg-1 of NAC 30 min after receiving AlP). The animals were then anaesthetised and ECG, blood pressure, and heart rate were recorded for 120 min. Treatment with AlP alone and in combination with NAC was associated with progressive hypotension, tachycardia, and ECG disturbances in rats, resulting in 100 % mortality 3 h after poisoning. However, DHA achieved 100 % survival in the poisoned rats and prevented AlP-induced ECG and haemodynamic abnormalities. The main mechanism of DHA in the treatment of AlP poisoning is unclear, but the findings suggest the promising therapeutic potential of DHA against AlP poisoning.
Topics: Aluminum Compounds; Animals; Dihydroxyacetone; Male; Pesticides; Phosphines; Poisoning; Rats; Shock, Cardiogenic
PubMed: 29990298
DOI: 10.2478/aiht-2018-69-3106 -
The Journal of General and Applied... Jun 2023Corynebacterium glutamicum was metabolically engineered to produce phenylalanine, a valuable aromatic amino acid that can be used as a raw material in the food and...
Corynebacterium glutamicum was metabolically engineered to produce phenylalanine, a valuable aromatic amino acid that can be used as a raw material in the food and pharmaceutical industries. First, a starting phenylalanine-producer was constructed by overexpressing tryptophan-sensitive 3-deoxy-D-arabino-heptulosonate-7-phosphate synthase and phenylalanine- and tyrosine-insensitive bifunctional enzyme chorismate mutase prephenate dehydratase from Escherichia coli, followed by the inactivation of enzymes responsible for the formation of dihydroxyacetone and the consumption of shikimate pathway-related compounds. Second, redirection of the carbon flow from tyrosine to phenylalanine was attempted by deleting of the tyrA gene encoding prephenate dehydrogenase, which catalyzes the committed step for tyrosine biosynthesis from prephenate. However, suppressor mutants were generated, and two mutants were isolated and examined for phenylalanine production and genome sequencing. The suppressor mutant harboring an amino acid exchange (L180R) on RNase J, which was experimentally proven to lead to a loss of function of the enzyme, showed significantly enhanced production of phenylalanine. Finally, modifications of phosphoenolpyruvate-pyruvate metabolism were investigated, revealing that the inactivation of either phosphoenolpyruvate carboxylase or pyruvate carboxylase, which are enzymes of the anaplerotic pathway, is an effective means for improving phenylalanine production. The resultant strain, harboring a phosphoenolpyruvate carboxylase deficiency, synthesized 50.7 mM phenylalanine from 444 mM glucose. These results not only provided new insights into the practical mutations in constructing a phenylalanine-producing C. glutamicum but also demonstrated the creation of a potential strain for the biosynthesis of phenylalanine-derived compounds represented by plant secondary metabolites.
Topics: Phenylalanine; Corynebacterium glutamicum; Metabolic Engineering; Tyrosine; Escherichia coli
PubMed: 35989300
DOI: 10.2323/jgam.2022.08.002 -
Frontiers in Plant Science 2022The regulatory protein CP12 can bind glyceraldehyde 3-phosphate dehydrogenase (GapDH) and phosphoribulokinase (PRK) in oxygenic phototrophs, thereby switching on and off...
The regulatory protein CP12 can bind glyceraldehyde 3-phosphate dehydrogenase (GapDH) and phosphoribulokinase (PRK) in oxygenic phototrophs, thereby switching on and off the flux through the Calvin-Benson cycle (CBC) under light and dark conditions, respectively. However, it can be assumed that CP12 is also regulating CBC flux under further conditions associated with redox changes. To prove this hypothesis, the mutant Δ of the model cyanobacterium sp. PCC 6803 was compared to wild type and different complementation strains. Fluorescence microscopy showed for the first time the kinetics of assembly and disassembly of the CP12-GapDH-PRK complex, which was absent in the mutant Δ. Metabolome analysis revealed differences in the contents of ribulose 1,5-bisphosphate and dihydroxyacetone phosphate, the products of the CP12-regulated enzymes GapDH and PRK, between wild type and mutant Δ under changing CO conditions. Growth of Δ was not affected at constant light under different inorganic carbon conditions, however, the addition of glucose inhibited growth in darkness as well as under diurnal conditions. The growth defect in the presence of glucose is associated with the inability of Δ to utilize external glucose. These phenotypes could be complemented by ectopic expression of the native CP12 protein, however, expression of CP12 variants with missing redox-sensitive cysteine pairs only partly restored the growth with glucose. These experiments indicated that the loss of GapDH-inhibition CP12 is more critical than PRK association. Measurements of the NAD(P)H oxidation revealed an impairment of light intensity-dependent redox state regulation in Δ Collectively, our results indicate that CP12-dependent regulation of the CBC is crucial for metabolic adjustment under conditions leading to redox changes such as diurnal conditions, glucose addition, and different CO conditions in cyanobacteria.
PubMed: 36330266
DOI: 10.3389/fpls.2022.1028794 -
Journal of the American Chemical Society Oct 2021A cell-free enantioselective transformation of the carbon atom of CO has never been reported. In the urgent context of transforming CO into products of high value, the...
A cell-free enantioselective transformation of the carbon atom of CO has never been reported. In the urgent context of transforming CO into products of high value, the enantiocontrolled synthesis of chiral compounds from CO would be highly desirable. Using an original hybrid chemoenzymatic catalytic process, we report herein the reductive oligomerization of CO into C (dihydroxyacetone, DHA) and C (l-erythrulose) carbohydrates, with perfect enantioselectivity of the latter chiral product. This was achieved with the key intermediacy of formaldehyde. CO is first reduced selectively by 4e by an iron-catalyzed hydroboration reaction, leading to the isolation and complete characterization of a new bis(boryl)acetal compound derived from dimesitylborane. In an aqueous buffer solution at 30 °C, this compound readily releases formaldehyde, which is then involved in selective enzymatic transformations, giving rise either (i) to DHA using a formolase (FLS) catalysis or (ii) to l-erythrulose with a cascade reaction combining FLS and d-fructose-6-phosphate aldolase (FSA) A129S variant. Finally, the nature of the synthesized products is noteworthy, since carbohydrates are of high interest for the chemical and pharmaceutical industries. The present results prove that the cell-free synthesis of carbohydrates from CO as a sustainable carbon source is a possible alternative pathway in addition to the intensely studied biomass extraction and syntheses from fossil resources.
PubMed: 34546049
DOI: 10.1021/jacs.1c07872 -
Bioresources and Bioprocessing Jul 2022Catalytic valorization of raw glycerol derived from biodiesel into high-value chemicals has attracted great attention. Here, we report chemoenzymatic cascade reactions...
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-SpNox at 30 °C. Subsequently, NaOH or NaClO 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.
PubMed: 38647569
DOI: 10.1186/s40643-022-00561-z -
Proceedings of the National Academy of... Apr 2018Methane can be converted to triose dihydroxyacetone (DHA) by chemical processes with formaldehyde as an intermediate. Carbon dioxide, a by-product of various industries...
Methane can be converted to triose dihydroxyacetone (DHA) by chemical processes with formaldehyde as an intermediate. Carbon dioxide, a by-product of various industries including ethanol/butanol biorefineries, can also be converted to formaldehyde and then to DHA. DHA, upon entry into a cell and phosphorylation to DHA-3-phosphate, enters the glycolytic pathway and can be fermented to any one of several products. However, DHA is inhibitory to microbes due to its chemical interaction with cellular components. Fermentation of DHA to d-lactate by strain TG113 was inefficient, and growth was inhibited by 30 g⋅L DHA. An ATP-dependent DHA kinase from (pDC117d) permitted growth of strain TG113 in a medium with 30 g⋅L DHA, and in a fed-batch fermentation the d-lactate titer of TG113(pDC117d) was 580 ± 21 mM at a yield of 0.92 g⋅g DHA fermented. strain LW225, with a higher glucose flux than , produced 811 ± 26 mM d-lactic acid at an average volumetric productivity of 2.0 g⋅L⋅h Fermentation of DHA required a balance between transport of the triose and utilization by the microorganism. Using other engineered strains, we also fermented DHA to succinic acid and ethanol, demonstrating the potential of converting CH and CO to value-added chemicals and fuels by a combination of chemical/biological processes.
Topics: Dihydroxyacetone; Escherichia coli; Fermentation; Glucose; Klebsiella; Lactic Acid; Metabolic Engineering; Microorganisms, Genetically-Modified
PubMed: 29632200
DOI: 10.1073/pnas.1801002115