Explore the vast range of titles available.

The ability to predict the behaviour of high-pressure mixtures of carbon dioxide and alcohol is important for industrial purposes. The equilibrium composition of three binary carbon dioxide-alcohol systems was measured at temperatures of 313.15 K and 333.15 K and at pressures of up to 100 bar for carbon dioxide-2-propanol, up to 160 bar for carbon dioxide-1-butanol and up to 150 bar for carbon dioxide-2-butanol. Different equilibrium compositions of carbon dioxide in alcohols were observed despite their similar molecular weight (M2-propanol = 60.100 g mol−1, M1-butanol = 74.121 g mol−1 and M2-butanol = 74.122 g mol−1) and place in the functional hydroxyl group (first or second carbon molecule). It is assumed that the differences in the phase equilibria are due to different vapor pressures, polarities and solute-solute interactions.

2-Butanol is a promising biofuel due to its favorable properties and lower microbial toxicity compared to other butanol isomers. However, microbial production remains challenging due to the absence of a native biochemical pathway for directly converting sugars into 2-butanol. To achieve this goal, glucose should be directed through the 2,3-butanediol (2,3-BD) pathway, involving α-acetolactate synthase, α-acetolactate decarboxylase, and butanediol dehydrogenase for the formation of meso-2,3-BD, followed by diol dehydratase-catalyzed conversion of meso-2,3-BD to butanone and alcohol dehydrogenase-mediated reduction in butanone to 2-butanol. In this study, we report the development of six new recombinant strains based on Klebsiella pneumoniae G31, in which the metabolic pathway for converting glucose to meso-2,3-BD was extended to 2-butanol. All engineered strains harbored the vitamin B12-dependent diol dehydratase complex (pduCDEGH) from Lentilactobacillus diolivorans DSM 14421 under its native promoter control. In addition, pduQ from the same strain, and adh from Clostridium beijerinckii DSM 51 encoding alcohol dehydrogenases were expressed under native, T7, or Ptac promoters. The highest yield of 2-butanol from glucose was achieved by K. pneumoniae K6 carrying the adh gene under the control of the T7 promoter—437 mg/L. Using 2-butanone as a substrate, K6 again produced the highest titer of 2-butanol (3.9 g/L), followed by the recombinant K8 (with adh under the Ptac promoter), and notably, by the native K. pneumoniae strains. Therefore, although pduQ encodes a key alcohol dehydrogenase in L. diolivorans, it has weaker properties than adh for the K. pneumoniae host in all promoter configurations. As the high expression levels of adh under T7 promoter control were driven by the native bacterial RNA polymerase, this promoter–host combination appears particularly suitable for developing other strains of industrial relevance.

The unique fuel characteristics of butanol and the possibility of its microbial production make it one of the most desirable environmentally friendly substitutes for petroleum fuels. However, the highly toxic nature of 1-butanol to the bacterial strains makes it unprofitable for commercial production. By comparison, 2-butanol has similar fuel qualities, and despite the difficulties in its microbial synthesis, it holds promise because it may be less toxic. This paper is the first comprehensive study to compare bacterial tolerance to different butanol isomers by examining the growth of 31 bacterial strains under 1-butanol and 2-butanol stress conditions. The presented results reveal that all tested strains showed a higher tolerance to 2-butanol than to 1-butanol at each solvent concentration (1%, 2%, and 3% v/v). Moreover, with an increased solvent concentration, bacterial cells lost their resistance to 1-butanol more rapidly than to 2-butanol. A comparison of the transcriptome profiles of the reference strains Bacillus subtilis ATCC 168 and E. coli ATCC 25922 disclosed a specific response to butanol stress. Most notably, in the presence of 2-butanol E. coli ATCC 25922 showed a reduced expression of genes for chaperones, efflux pumps, and the flagellar apparatus, as well as an enhancement of membrane and electron transport. B. subtilis, with 2-butanol, did not perform emergency sporulation or escape, as some global transcriptional stress response regulators were downregulated. The overexpression of ribosomal RNAs, pyrimidine biosynthesis genes, and DNA- and RNA-binding proteins such as pcrA and tnpB was crucial in the response.

A cascade strategy for the catalytic valorization of aqueous solutions of levulinic acid as well as of γ-valerolactone to 2-methyltetrahydrofuran or to monoalcohols, 2-butanol and 2-pentanol, has been studied and optimized. Only commercial catalytic systems have been employed, adopting sustainable reaction conditions. For the first time, the combined use of ruthenium and rhenium catalysts supported on carbon, with niobium phosphate as acid co-catalyst, has been claimed for the hydrogenation of γ-valerolactone and levulinic acid, addressing the selectivity to 2-methyltetrahydrofuran. On the other hand, the use of zeolite HY with commercial Ru/C catalyst favors the selective production of 2-butanol, starting again from γ-valerolactone and levulinic acid, with selectivities up to 80 and 70 mol %, respectively. Both levulinic acid and γ-valerolactone hydrogenation reactions have been optimized, investigating the effect of the main reaction parameters, to properly tune the catalytic performances towards the desired products. The proper choice of both the catalytic system and the reaction conditions can smartly switch the process towards the selective production of 2-methyltetrahydrofuran or monoalcohols. The catalytic system [Ru/C + zeolite HY] at 200 °C and 3 MPa H2 is able to completely convert both γ-valerolactone and levulinic acid, with overall yields to monoalcohols of 100 mol % and 88.8 mol %, respectively.

RS-4-(4-hydroxyphenyl)-2-butanol (rhododendrol (RD))—a skin-whitening ingredient—was reported to induce leukoderma in some consumers. We have examined the biochemical basis of the RD-induced leukoderma by elucidating the metabolic fate of RD in the course of tyrosinase-catalyzed oxidation. We found that the oxidation of racemic RD by mushroom tyrosinase rapidly produces RD-quinone, which gives rise to secondary quinone products. Subsequently, we confirmed that human tyrosinase is able to oxidize both enantiomers of RD. We then showed that B16 cells exposed to RD produce high levels of RD-pheomelanin and protein-SH adducts of RD-quinone. Our recent studies showed that RD-eumelanin—an oxidation product of RD—exhibits a potent pro-oxidant activity that is enhanced by ultraviolet-A radiation. In this review, we summarize our biochemical findings on the tyrosinase-dependent metabolism of RD and related studies by other research groups. The results suggest two major mechanisms of cytotoxicity to melanocytes. One is the cytotoxicity of RD-quinone through binding with sulfhydryl proteins that leads to the inactivation of sulfhydryl enzymes and protein denaturation that leads to endoplasmic reticulum stress. The other mechanism is the pro-oxidant activity of RD-derived melanins that leads to oxidative stress resulting from the depletion of antioxidants and the generation of reactive oxygen radicals.

Nanocrystalline Fe 2 O 3 -NiO composite catalysts were prepared using a sonication-assisted green preparation method. The prepared catalysts were characterized using different techniques, including thermal analyses (TGA/DTA), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy, surface area measurements (S BET ), and scanning electron microscopy (SEM). The surface basicity of the prepared catalysts was measured using the temperature-programmed desorption of CO 2 (CO 2 -TPD) as a highly acidic probe molecule. The catalytic activity of all the prepared catalysts was tested at a temperature range of 250–325 °C towards the dehydrogenation of 2-butanol to methyl-ethyl ketone (MEK), which is considered a promising fossil fuel alternative and has several industrial applications. The composite catalysts showed better catalytic activity compared to the pure oxides (i.e., Fe 2 O 3 and NiO) due to the strong synergetic effect between the two oxides. Fe 2 O 3 prevented the coke formation over the surface of NiO by the oxygen-scavenging effect of Fe, which promotes the oxidation of the carbonaceous species and increases the catalyst’s resistance to deactivation. The effect of weight hourly space velocity (WHSV) on the catalytic activity was tested over a selected catalyst. In addition, the stability and durability of the catalyst were tested across four successive reaction cycles, demonstrating remarkable performance throughout all the reaction cycles. Graphical Abstract

The purpose of this paper is to develop SRF formulations for LHP performance enhancement. In this paper, the solute of SRF is prepared, and butanol and its isomer, 2-butanol, are selected. In this paper, concentrations of the 2-butanol aqueous solution (10%, 15%, and 20%) plus the butanol 6% aqueous solution were used to measure the surface tension of four different formulations of SRF and water. It was found that the higher the solute concentration became, the stronger the Marangoni effect was, and the more obvious the surface tension change of the 2-butanol 20% aqueous solution was. Water, the butanol 6% aqueous solution and the 2-butanol 20% aqueous solution were filled into LHP respectively, and the heat transfer performance was measured. The 2-Butanol 20% aqueous solution improved LHP performance by about three times compared with water, and the lowest total thermal resistance was only 1/4 that of water. Therefore, the 2-butanol 20% SRF aqueous solution is an ideal formula for improving the LHP heat transfer performance.

Real-time quaking-induced conversion (RT-QuIC) is highly sensitive for prion detection; however, inhibitory factors present in tissue homogenates readily interfere with the assay. We previously reported that recombinant cervid prion protein (rCerPrP) enabled the establishment of practical RT-QuIC for detecting chronic wasting disease and atypical bovine spongiform encephalopathy (BSE) prions, i.e., detecting low levels of prions in high concentration of brain tissue homogenates. Accordingly, the present study aimed to establish RT-QuIC for detecting classical BSE (C-BSE) and classical and atypical scrapie (C- and A-scrapie, respectively). A single-step lipid extraction using a 3:1 mixture of 2-butanol and methanol was effective as a pretreatment to remove inhibitors from brain homogenates. Among three rPrPs extensively evaluated, recombinant sheep PrP (rShPrP) was the most suitable substrate for practical detection of C-BSE prions. rCerPrP-173S/177N and rCerPrP-98S/173S/177N, which carry sheep-type amino acid substations at codons 173 and 177 and at codons 98, 173, and 177, showed excellent performance for detecting C-scrapie prions. Moreover, rCerPrP-98S/173S/177N, but not rCerPrP-173S/177N, was identified as an optimal substrate for detecting A-scrapie prions. These results suggested that combining inhibitor-removal pretreatment with the optimization of rPrP substrate for each animal prions further enhanced of RT-QuIC performance.

In the present study, low-cost iron oxide catalysts have been prepared by a simple precipitation method using tin food can waste as a source of iron and sodium hydroxide or ammonium hydroxide solution as a precipitating agent. The prepared catalysts were characterized by thermogravimetric analysis (TGA), differential thermal analysis (DTA), X-ray diffraction (XRD), FT-IR spectra, scanning electron microscopy (SEM), EDAX quantitative elemental analysis, and BET surface area measurements. Surface basicity of iron oxide catalysts was measured by adsorption of carbon dioxide as an acidic probe molecule, followed by desorption measurements using the TGA technique. The prepared iron oxide catalysts were tested by dehydrogenation of 2-butanol to methyl ethyl ketone (MEK) at a temperature range of 275–375 °C. Commercial iron oxide was tested under identical reaction conditions for comparison with the prepared catalysts. The results indicated the superiority of the prepared catalysts over the commercial one and the superiority of the catalyst prepared using NaOH over that prepared using NH4OH as precipitating agents. The use of different precipitating agents affects the surface morphology and, consequently, the catalytic activity of the produced iron oxide catalysts.

In this study, V2O5/ZrO2 samples loaded with different wt% of V2O5, ranging between 0% and 20% (wt% = 2.5, 3.6, 7.5, 10, and 20), were prepared and studied in the dehydrogenation of 2-butanol in order to investigate their acid-basic properties and to select the most interesting sample, that was identified in the 3.6 wt%V2O5/ZrO2. Such a catalyst was modified by adding phosphate at different atomic ratios (P/V = 0.5, 1, and 2) and further characterized by XRD, SEM-EDX, ESR, UV-Vis-PIR diffuse reflectance. Tests of catalytic dehydrogenation of 2-butanol were also performed. Then, the so-prepared samples were investigated in the oxidative dehydrogenation (ODH) of propane that represents the reaction of main interest in this study. It has been shown that the introduction of 3.6 wt%V2O5 and phosphate in the zirconia matrix enhances the stability of the tetragonal structure, improves acidity, and promotes ODH activity. Compared to the unpromoted 3.6 wt%V2O5/ZrO2 catalyst, the addition of phosphate increases the overall propane conversion from 12% to 20%, and also the propylene selectivity from 54% to near 64%, in the experimental conditions F °C3H8/F°O2/F°total (cm3/min): 3.6/1.8/60 at the temperature of 500 °C. The influence of the reaction mixture on the ODH, in particular the oxygen flow rate, was addressed. Highlights: Phosphorus loaded V2O5/ZrO2 catalysts were prepared and investigated in the oxidative dehydrogenation of propane. Addition of V2O5 and phosphorus to ZrO2 stabilized the tetragonal phase with respect to the monoclinic one. Among the prepared V2O5/ZrO2 samples, the most active catalyst corresponds to 3.6 wt% of V2O5/ ZrO2, The addition of phosphorus to 3.6 wt% V2O5/ZrO2 improves acidity and selectivity to propylene. Correlation between catalysts acidity and oxidative dehydrogenation of propane was observed.