Dehydration Mechanism Research Articles

Noble Metal Promoted TiO2 from Silver-Waste Valorisation: Synergism between Ag and Au

Wastewaters from precious metal industries contain high amounts of noble metals, but their efficient recycling is hindered by the wastewater complex composition. Here, we propose an innovative approach for the efficient recovery of noble metals contained in these metal-enriched wastewaters as precursors for the synthesis of noble metal nanoparticles (NPs) and supported metal catalysts. Silver NPs were synthesized from Ag-enriched wastewater and then deposited on TiO2 to prepare photocatalysts. Then, further promotion of the photocatalytic activity of Ag-modified TiO2 was achieved by the addition of as little as 0.5 wt.% of Au. STEM-EDS analyses proved that Au NPs were located on Ag or AgOx nanoparticles. The contact between the two metal-containing NPs results in charge transfer effects, appreciable both in terms of oxidation states determined by XPS and of optical properties. In particular, the plasmon band of Au NPs shows photochromic effects: under UV light irradiation, bimetallic samples exhibit a blue-shift of the plasmon band, which is reversible under dark storage. The activity of the materials was tested towards ethanol photodegradation under UV light. Adding 0.5 wt.% Au NPs resulted in a promoted activity compared to Ag-TiO2, thus showing synergistic effects between Au and Ag. Ethanol was completely converted already after 1 h of UV irradiation, acetaldehyde was formed as the main oxidation product and fully degraded in less than 180 min. Notably, bimetallic samples showed ethylene formation by a parallel dehydration mechanism.

Production of rods for steel and iron casting from mixtures with a binder based on a combination of inorganic salts

Recently, there has been an active search and development of non-scarce and suitable for industrial use inorganic binders that can compete with synthetic resins in the composition of core mixtures in the production of castings, while ensuring comfortable working conditions for the personnel of foundries and reducing harmful emissions during the entire production process. To date, this goal has not yet been achieved and the search has not been completed, so research continues. The work, the results of which are presented by the authors of this article, is one of many ongoing in Russia in the mainstream of the designated topic. The authors decided to assign the role of the binder in the composition of the core mixture to the composition of inorganic salts, one of which is liquid glass - an aqueous solution of sodium or potassium silicates, and the other (others) are simultaneously hydrophilic and highly soluble in water salts of alkali or alkaline earth metals. The work focuses on the group of complex double salts, crystalline hydrates of sulfates of tri- and monovalent metals - the so-called alum, which have the required set of properties, and, in particular, on non-deficient potassium alum, which had previously proven itself well as a technological additive to the liquid glass core mixture. An environmentally friendly, easy-toimplement version of the technology has been proposed, experimentally verified and tested under the conditions of existing production, which provides the curing of the rod by the mechanism of dehydration of the rod mixture by a combination of heat exposure and the imposition of vacuum and the achievement of the required level of operational characteristics. Practical testing has confirmed the effectiveness of the application of the developed technology for the production of castings from iron and steel. Currently, work is underway to expand its application in foundries of Russian enterprises.

Glucose Conversion to 5-(Hydroxymethyl)furfural (5-HMF) using Microwave Radiation and Titanium Dioxide

In this project, the focus is placed on the reaction optimizations to produce 5-hydroxymethylfurfural (5-HMF), a common chemical building block to other industrially useful derivatives. The main objective of this study is to determine the feasibility of using different forms of TiO2 as a catalyst to acquire 5-HMF from monosaccharides by an effi cient, economical, and environment-friendly process. The use of three different forms of TiO2 (anatase, rutile, and P-25) as a catalyst, for the glucose dehydration process in this study, has never been reported in past literature. The heating by microwave radiation is introduced to the reaction, which requires elevated temperature, to reduce both the required reaction time and temperature. TiO2, the heterogeneous catalyst for the dehydration mechanism, was fi ltered off, while the 5-HMF dissolved and stayed in the aqueous solution. The three TiO2 catalyst forms are separately utilized to optimize reaction conditions. Anatase form is shown to be the most effective at catalyzing the dehydration process. The reaction temperature of 187 ºC; anatase as a catalyst; and reaction time of 5 minutes led to the optimal outcome in this project. The maximum 5-HMF yield obtained in this study is 12.84%, which is in-between the 6.10-18.60% 5-HMF yield range acquired by Qi et al., 2008. Moreover, a catalyst/substrate weight ratio of 1:10 was used in this study, compared to the 1:2 ratio used by Qi et al., 2008. Hence, this project reduced the amount of catalyst required to obtain a signifi cant 5-HMF yield, and successfully demonstrated that the anatase form of TiO2 is a viable catalyst for the dehydration of monosaccharides to 5-HMF.

Аналіз технічних рішень для зневоднення та класифікації за крупністю мінеральної сировини при тонкому і надтонкому вібраційному грохоченні

The article is aimed at studying new technical solutions for dehydration and size classification in the case of fine and ultrafine vibratory screening of mineral raw materials. It is shown that the moisture content in many products is limited by GOST or temporary regulations. Water is the ballast in their transportation. An excessive amount of water contributes to the freezing of raw materials in winter conditions and causes great difficulties in unloading them from wagons. Traditional methods make it possible to effectively separate only materials with a particle size of more than 1 mm, and reduce the moisture content of the finished product to 18-22%, depending on the size, which does not meet the required standards. It is necessary to reduce moisture to 8-10% or less. In addition, the processing of various raw materials in most cases requires, simultaneously with dehydration, the separation of products of a wide range of sizes. To overcome the adhesion forces between wet particles, different excitations are used, one of which is a combined excitation that provides intensive movement of the liquid and particles relative to each other. Combined means excitation with various combinations of polyfrequency, impulse dynamic effects, and additional effects of various physical fields are also possible. The use of polyfrequency and impulse dynamic (“single impacts”) impacts on the MVG2.0 vibrating polyfrequency screen makes it possible to effectively separate the solid phase from the liquid when treating recycled water with a particle size of 20 microns. At the same time, the residual moisture in the oversize product is no more than 17%. The method of complex dehydration of wet mineral raw materials, combining three dehydration mechanisms (vibration, electrokinetic and vacuum), concentrated in one device, allows, at different initial moisture content of the raw material, to reduce the moisture content from 30 to 16%, from 20 to 14% and from 10 to 6%, t .e. reduce the humidity from 30 to 6% in several stages. These results were obtained for narrow size classes of 0.25÷0.63 mm. The use of modes with "double impacts" and disintegrating elements in the new vibro-impact screen made it possible to reduce the humidity from 30% to 8-10%. The separation efficiency of the +0–0.1 mm class was up to 65–70%. When using an activator, the moisture content of the material is reduced from 30% to 7-9%, and the separation efficiency of the +0-0.1 mm class is increased to 70-75%. Due to the use of a disintegrator over the activator, the moisture content of the oversize product was reduced to 6–8%, while the separation efficiency of the +0–0.1 mm class increased to 75–80%. Experimental method on the model of a vibro-impact screen for different fineness classes determined the conditions under which the maximum extraction of the class +0–0.1 mm and the decrease in humidity are determined. Currently, work is underway aimed at creating a vibro-impact screen, which will implement: expanding the range of impact on the processed material, increasing the life of the screen, the possibility of operational automatic control, increasing the stability of work and, at the same time, simplicity of design.

TMT-Based Quantitative Proteomic Analysis Reveals the Physiological Regulatory Networks of Embryo Dehydration Protection in Lotus (Nelumbo nucifera).

Lotus is an aquatic plant that is sensitive to water loss, but its seeds are longevous after seed embryo dehydration and maturation. The great difference between the responses of vegetative organs and seeds to dehydration is related to the special protective mechanism in embryos. In this study, tandem mass tags (TMT)-labeled proteomics and parallel reaction monitoring (PRM) technologies were used to obtain novel insights into the physiological regulatory networks during lotus seed dehydration process. Totally, 60,266 secondary spectra and 32,093 unique peptides were detected. A total of 5,477 proteins and 815 differentially expressed proteins (DEPs) were identified based on TMT data. Of these, 582 DEPs were continuously downregulated and 228 proteins were significantly up-regulated during the whole dehydration process. Bioinformatics and protein-protein interaction network analyses indicated that carbohydrate metabolism (including glycolysis/gluconeogenesis, galactose, starch and sucrose metabolism, pentose phosphate pathway, and cell wall organization), protein processing in ER, DNA repair, and antioxidative events had positive responses to lotus embryo dehydration. On the contrary, energy metabolism (metabolic pathway, photosynthesis, pyruvate metabolism, fatty acid biosynthesis) and secondary metabolism (terpenoid backbone, steroid, flavonoid biosynthesis) gradually become static status during lotus embryo water loss and maturation. Furthermore, non-enzymatic antioxidants and pentose phosphate pathway play major roles in antioxidant protection during dehydration process in lotus embryo. Abscisic acid (ABA) signaling and the accumulation of oligosaccharides, late embryogenesis abundant proteins, and heat shock proteins may be the key factors to ensure the continuous dehydration and storage tolerance of lotus seed embryo. Stress physiology detection showed that H2O2 was the main reactive oxygen species (ROS) component inducing oxidative stress damage, and glutathione and vitamin E acted as the major antioxidant to maintain the REDOX balance of lotus embryo during the dehydration process. These results provide new insights to reveal the physiological regulatory networks of the protective mechanism of embryo dehydration in lotus.

Crystal Structures and Solution Chemical Properties of Two Lactate Complexes Mn[(C3H5O3)2(H2O)2]⋅H2O(s) and Cu(C3H5O3)2(s)

Trihydrated manganese lactate Mn[(C3H5O3)2(H2O)2]⋅H2O(s) and anhydrous copper lactate Cu(C3H5O3)2(s) were synthesized. Crystal structures of the two compounds were characterized by X-ray single crystal diffraction technique. The compositions, spatial structures and coordination modes of the two compounds were determined by analysis of their molecular structures and crystal structures. Lattice potential energies of the compounds were calculated by using the crystallographic data. Molar enthalpies of dissolution of these metal complexes in the ultrapure water were measured by an isoperibol solution-reaction calorimeter with an accuracy of ±0.3%. On the basis of Pitzer's electrolyte solution theory, infinite dilution molar enthalpies of dissolution and Pitzer's parameters of the two lactate complexes soluble in water at T = 298.15 K were calculated. The infinite dilution molar enthalpies (ΔsHm∞) of dissolution of the title compounds were combined with lattice potential energies (UPOT) by a designed thermodynamic cycle, and the average molar enthalpy of hydration of the common lactate ion was calculated to be (407.207 ± 0.038) kJ·mol−1. The mechanism of thermal decomposition or dehydration of the trihydrated manganese lactate was explored by TG-DSC technique, and the difference between molar enthalpies (ΔsHm) of dissolution of trihydrated manganese lactate and anhydrous copper lactate at the same concentration was revealed.

Dehydration mechanisms in electrohydrodynamic drying of plant-based foods

Electrohydrodynamic drying (EHDD) is an energy-efficient and non-thermal technique for dehydrating heat-sensitive biological materials, like fruits, vegetables, or medicinal plants. Although this method has been studied for more than three decades, still little is known about the relative contribution of the different dehydration mechanisms in EHDD. An accurate understanding of the impact of the different EHD-driven mass transfer processes inside the food and its surrounding air is essential for a targeted future optimization and successful upscaling of EHDD technology. Examples of these dehydration mechanisms are convective moisture removal, electroporation of the cell membrane, or electro-osmotic flow in the fruit. In this modeling study, we first identify possible dehydration mechanisms for mass transfer during the EHDD process of plant-based food materials. Using available theoretical models, we then estimate the relative contribution of each dehydration mechanism to the overall mass transfer during the constant rate period and rank them based on their contribution. We show that convective dehydration by ionic wind is the dominant dehydration mechanism, with a contribution of about 93% to the overall water flux for a capillary-porous material. Cell-membrane electroporation is the second important driving force that increases the contribution of the transmembrane water flow to about 6.5% of the total mass flux in fruit tissue. The contribution of all the other water transport mechanisms is only 0.5%. These insights provide a stepping stone towards developing a full physics-based model of the dehydration process by EHD, including the falling rate period.

Crystal structure and solution thermodynamics of the lactate complex Zn[(C3H5O3)2(H2O)2]⋅H2O(s)

An important trihydrated lactate complex Zn[(C3H5O3)2(H2O)2]⋅H2O(s) was synthesized. Crystal structure was characterized by X-ray single crystal diffractometer, and molecular structure, spatial structure and coordination mode of the complex were determined. The lattice potential energy of the complex was calculated by crystal data. The enthalpy of dissolution of the compound in the water was measured by isoperibol reaction calorimeter with an accuracy of ±0.3%. According to the Pitzer electrolyte solution theory, molar enthalpy of dissolution at the infinite dilution and Pitzer parameters of the compound soluble in water at T = 298.15 K were calculated. Combined with molar enthalpy of dissolution in the infinite dilution (ΔsHm∞) and lattice potential energy (UPOT), enthalpy of hydration of lactate ion was calculated. Mechanism of thermal analysis or dehydration of the compound was explained by TG-DSC technique.

Study on demulsifier crude oil interactions at oil-water interface for crude oil dehydration

Stabilization mechanisms of water-in-oil emulsions have been well studied. The process of dehydration with demulsifiers in these previous works have focused primarily on macro scale bottle tests or on microscale investigations of asphaltene film. A connection between the two scales, however, is necessary to better understand the mechanisms of dehydration using demulsifiers. In our present work, results from bottle tests of undiluted crude oil were compared with the coalescence process of water droplets in solvent diluted crude oil and with visualization experiments of the interfacial film rigidity through observing the crumpling of water droplets in diluted crude oil. To gain further insight into the molecular interactions between the native surface active materials and three different polymeric demulsifiers at the solvent-water interface, Langmuir interfacial isotherms were measured using diluted crude oil-water systems with and without the addition of demulsifiers. The highest water removal percentage was obtained though the addition of a random biopolymer demulsifier, butyl acrylate/2-(dimethylamino) ethyl acrylate (P1), that also rendered the shortest coalescence time of the three polymers tested, indicating the importance of coalescence behavior in dehydration. In addition, the smallest crumpling ratio which corresponds to lowest rigidity was detected for the P1 treated interface. For the first time, we observed that the diluted crude oil-water interfacial film collapsed easily upon compression with the administration of the very efficient demulsifier P1. It was found that the collapse pressure can be used as a measure of the rigidity of very soft interfacial films that may not be measurable directly by compression energy. Based on the close relation between the dehydration process and the interaction between demulsifiers and natural active surfactants, it can be deduced that, efficient demulsifiers essentially disrupt the continuity of the asphaltenic interfacial films and reduce the strength of anchoring of these natural surfactants at the interface, allowing for the collapse of segments and resulting in efficient dehydration.

Furosemide-induced systemic dehydration alters the proteome of rabbit vocal folds

Whole-body dehydration (i.e., systemic dehydration) leads to vocal fold tissue dehydration. Furosemide, a common diuretic prescribed to treat hypertension and edema-associated conditions, induces systemic dehydration. Furosemide also causes voice changes in human speakers, making this method of systemic dehydration particularly interesting for vocal fold dehydration studies. Our objective was to obtain a comprehensive proteome of vocal folds following furosemide-induced systemic dehydration. New Zealand White rabbits were used as the animal model and randomly assigned to euhydrated (control) or furosemide-dehydrated groups. Systemic dehydration, induced by injectable furosemide, was verified by an average body weight loss of −5.5% and significant percentage changes in blood analytes in the dehydrated rabbits compared to controls. Vocal fold specimens, including mucosa and muscle, were processed for proteomic analysis using label-free quantitation LC-MS/MS. Over 1600 proteins were successfully identified across all vocal fold samples; and associated with a variety of cellular components and ubiquitous cell functions. Protein levels were compared between groups showing 32 proteins differentially regulated (p ≤ 0.05) in the dehydrated vocal folds. These are mainly involved with mitochondrial translation and metabolism. The downregulation of proteins involved in mitochondrial metabolism in the vocal folds suggests a mechanism to prevent oxidative stress associated with systemic dehydration. SignificanceVoice disorders affect different population demographics worldwide with one in 13 adults in the United States reporting voice problems annually. Vocal fold systemic hydration is clinically recognized for preventing and treating voice problems and depends on optimal body hydration primarily achieved by water intake. Herein, we use the rabbit as a translatable animal model, and furosemide as a translatable method of systemic dehydration, to reveal a comprehensive proteomic profile of vocal fold mucosa and muscle in response to systemic dehydration. The significant subset of proteins differentially regulated due to furosemide-induced dehydration offer novel insights into the molecular mechanisms of systemic dehydration in the vocal folds. These findings also deepen our understanding of changes to tissue biology after diuretic administration.

Analysis of volatile composition released from torrefaction of empty fruit bunch

This paper presents the effect of torrefaction on constituents of empty fruit bunch (EFB) and volatile components analysis. Different torrefaction temperature ranging from 240 to 300 ℃ are employed where hemicellulose has been decomposed significantly. Cellulose and lignin show only slight degradation at investigated temperature. Volatile released from torrefaction of EFB has been collected and analyzed where only carbon monoxide and carbon dioxide non-condensable volatile components are detected. The two highest volatile fractions detected for condensable components are water and acetic acid. The formation of non-condensable and condensable volatile components are originated from dehydration and decarboxylation mechanisms during decomposition of hemicellulose.

Dehydration and Rehydration Mechanisms of Pharmaceutical Crystals: Classification Of Hydrates by Activation Energy

Dehydration strongly influences the stability of hydrate drug substances. Consequently, the ability to predict dehydration of crystalline hydrate using the intermolecular interactions of water molecules contained in the crystals is essential for drug development. The conventional method employed to predict the propensity for dehydration uses the dehydration temperature, which is related to how tightly water molecules are bound in the crystal lattice. However, it is difficult to predict the dehydration propensity of a particular hydrate using only the dehydration temperature because other kinetic factors affect dehydration behavior, such as intermolecular interactions, and drug-substance-to-water molar ratio in a hydrate. In this study, we explored the use of the dehydration activation energy Ea and rehydration behavior to classify 11 pharmaceutical hydrates into three classes according to their kinetic behavior related to the thermodynamic factors of hydrates. There is good agreement between these classes and hydrate crystal structures determined from single-crystal X-ray diffraction, and thus, the classification reflects their crystal structural features. We compared Ea to the dehydration temperatures for each class and found that Ea plays a crucial role and is better than the temperature for quantitative differentiation of the dehydration propensities in these hydrates.

Lactic acid conversion into acrylic acid and other products over natural and synthetic zeolite catalysts: theoretical and experimental studies

In the present study we are interested in designing theoretical and experimental approach for the production of acrylic acid (AA) from lactic acid (LA) over various zeolite catalysts: synthetic BEA and natural clinoptilolite CLI zeolites modified with metals (Sn, Co, Cu and Fe). The catalysts were prepared using an ion exchange method. In the theoretical studies the metal M-O-M dimers were found to be stable above oxygen bound with aluminium centres of BEA and CLI zeolites. The mechanism of direct lactic acid dehydration in Sn-, Co-, Cu- and Fe-BEA zeolites was found inside the zeolites pores and in the hierarchical/surface model. Experimentally, the investigated catalysts set trends in the following by-product formation: acrylic acid, pyruvic acid (PAC), 2,3-pentanedione (2,3-PD) or acetaldehyde (AC). Based on the collected results, the following types of LA conversion reactions can be proposed: dehydration to AA, decarboxylation to acetaldehyde, hydrogenation to 2,3-pentanedione, oxidation to acetic acid, reduction to propionic acid, oxidative dehydrogenation to pyruvic acid, condensation to 1,2-propanediol.

Vapor-phase dehydration of 1,4-butanediol to 1,3-butadiene over Y2Zr2O7 catalyst

• Vapor-phase catalytic dehydration of 1,4-butanediol was investigated over Y 2 Zr 2 O 7 catalysts. • 1,3-Butadiene together with 3-buten-1-ol, tetrahydrofuran, and propylene was produced depending on the conditions. • 1,3-Butadiene yield of 90% or higher was achieved over the Y 2 Zr 2 O 7 calcined at 700 °C in the dehydration at 360 °C. • An unsaturated alcohol such as 3-buten-1-ol is more reactive than 1- and 2-butanol over the Y 2 Zr 2 O 7 catalyst. • It is suggested that the C=C double bond of 3-buten-1ol affects an attractive interaction to anchor the Y 2 Zr 2 O 7 catalyst. Vapor-phase catalytic dehydration of 1,4-butanediol (1,4-BDO) was investigated over Y 2 O 3 -ZrO 2 catalysts. In the dehydration, 1,3-butadiene (BD) together with 3-buten-1-ol (3B1OL), tetrahydrofuran, and propylene was produced depending on the reaction conditions. In the dehydration over Y 2 O 3 -ZrO 2 catalysts with different Y contents at 325°C, Y 2 Zr 2 O 7 with an equimolar ratio of Y/Zr showed high selectivity to 3B1OL, an intermediate to BD. In the dehydration at 360°C, a BD yield higher than 90% was achieved over the Y 2 Zr 2 O 7 calcined at 700°C throughout 10 h. In the dehydration of 3B1OL over Y 2 Zr 2 O 7 , however, the catalytic activity affected by the calcination temperature is roughly proportional to the specific surface area of the sample. The highest activity of Y 2 Zr 2 O 7 calcined at 700 °C for the BD formation from 1,4-BDO is explained by the trade-off relation in the activities for the first-step dehydration of 1,4-BDO to 3B1OL and for the second-step dehydration of 3B1OL to BD. The higher reactivity of 3B1OL than saturated alcohols such as 1-butanol and 2-butanol suggests that the C=C double bond of 3B1OL induces an attractive interaction to anchor the catalyst surface and promotes the dehydration. A probable mechanism for the one-step dehydration of 1,4-BDO to BD was discussed.

Cover Image

The cover image is based on the Full Paper The mechanism of sorbitol dehydration in hot acidic solutions by Tomomi Kondo, Takehiko Sasaki and Motoyuki Shiga., https://doi.org/10.1002/jcc.26710.

The mechanism of sorbitol dehydration in hot acidic solutions.

Sugar alcohol dehydration in hot water is an important reaction that allows for environmentally friendly biomass conversion without the use of organic solvents. Here, we report a free-energy analysis by metadynamics (MTD) simulations based on ab initio density functional theory and semiempirical density-functional tight-binding method to understand the mechanism of dehydration reactions of d-sorbitol (SBT) in hot acidic water. Comparing the results of ab initio and semiempirical MTD, it was found that the latter gives a reliable free energy surface of SBT dehydration reaction, although the results vary upon the inclusion of dispersion correction. It was found that the reaction proceeds consistently via an SN 2 mechanism, whereby the free energy of protonation of the hydroxyl group created as an intermediate is affected by the acidic species. This mechanism was further verified by real-time trajectories started from the transition state using ab initio molecular dynamics simulations. The free energy barriers of the reaction pathways leading to five-membered ether products are lower than those leading to six-membered ether products, in agreement with experiment. This outcome can be ascribed, in part, to our finding that the reaction barrier of the pathway is correlated to the stability of the SBT confined conformation at the initial stage of the reaction.

Development of a reactive force field for [formula omitted]n[formula omitted], and the application to thermochemical energy storage

Calcium chloride salt hydrates (CaCl2·nH2O) have a high potential to be used as thermochemical storage material (TCM). However, specific material properties – e.g., slow diffusion, low thermal conductivity, melting temperature, and crystal stability – inhibits further implementation as robust TCM. Inherent bulk crystal defects like cracks, pores, and grain boundaries promoted during the (de) hydration cycle of the TCM, affect these material properties. Reactive force field molecular dynamics (ReaxFF-MD) is used to investigate CaCl2·nH2O (physical and chemical) properties, as well as the effect of crystal defects on them. In this sense, a new ReaxFF force field is developed, which can describe stable CaCl2·nH2O structures, accurate descriptions of crystal surface energies, and multiple material indicators like charges, reaction enthalpies, and radial distribution functions. The new force field is further used to investigate the thermal conductivity, dehydration echanisms/kinetics, and crack formation upon heating of the crystal. The thermal conductivity is found to be 1.1 and 0.5 W/mK for respectively CaCl2 and CaCl2·2H2O, which is in good agreement with experimental results. Additionally, we investigated the influence of grain boundaries and the salts’ anisotropic crystal morphology and found that both grain boundaries and the typical layered structure in z-direction lower the thermal conductivity. By investigating dehydration mechanisms, it is shown that initial dehydration is 1.9–2.5 times lower in the z-direction, also due to the typical layered morphology. For all directions, superficial dehydrated CaCl2 layers impede dehydration of core layers, but cracks and pores significantly promote it. These molecular-scale findings reveal nanoscale opportunities that could benefit the TCM.

The Unexplored Wealth of Microbial Secondary Metabolites: the Sphingobacteriaceae Case Study.

Research on secondary metabolites (SMs) has been mostly focused on Gram-positive bacteria, especially Actinobacteria. The association of genomics with robust bioinformatics tools revealed the neglected potential of Gram-negative bacteria as promising sources of new SMs. The family Sphingobacteriaceae belongs to the phylum Bacteroidetes having representatives in practically all environments including humans, rhizosphere, soils, wastewaters, among others. Some genera of this family have demonstrated great potential as plant growth promoters, bioremediators and producers of some value-added compounds such as carotenoids and antimicrobials. However, to date, Sphingobacteriaceae's SMs are still poorly characterized, and likewise, little is known about their chemistry. This study revealed that Sphingobacteriaceae pangenome encodes a total of 446 biosynthetic gene clusters (BGCs), which are distributed across 85 strains, highlighting the great potential of this bacterial family to produce SMs. Pedobacter, Mucilaginibacter and Sphingobacterium were the genera with the highest number of BGCs, especially those encoding the biosynthesis of ribosomally synthesized and post-translationally modified peptides (RiPPs), terpenes, polyketides and nonribosomal peptides (NRPs). In Mucilaginibacter and Sphingobacterium genera, M. lappiensis ATCC BAA-1855, Mucilaginibacter sp. OK098 (both with 11 BGCs) and Sphingobacterium sp. 21 (6 BGCs) are the strains with the highest number of BGCs. Most of the BGCs found in these two genera did not have significant hits with the MIBiG database. These results strongly suggest that the bioactivities and environmental functions of these compounds, especially RiPPs, PKs and NRPs, are still unknown. Among RiPPs, two genera encoded the production of class I and class III lanthipeptides. The last are associated with LanKC proteins bearing uncommon lyase domains, whose dehydration mechanism deserves further investigation. This study translated genomics into functional information that unveils the enormous potential of environmental Gram-negative bacteria to produce metabolites with unknown chemistries, bioactivities and, more importantly, unknown ecological roles.

Stepwise dehydration of Cd-exchanged levyne: thermal stability and structural modifications

Zeolites show remarkable properties that can be tuned through cation exchange of their original extraframework content. In this respect, the response of the modified zeolite to the heating stimuli, in terms of structural modifications and thermal stability, can drastically change and is, therefore, an important factor to consider. In this study, the dehydration mechanism of a natural levyne previously exchanged with Cd2+ has been monitored in situ by single crystal X-ray diffraction. The initial dehydration trend between 50 and 175 °C is similar to that observed for the pristine material, levyne-Ca. The water loss is accompanied by extraframework cation migration within the zeolitic cavities and the unit-cell volume slightly contracts from 3503.8(1) to 3467.8(6) Å3. From 200 to 250 °C, a pronounced drop of the unit-cell volume (− 7%) is observed. The dehydrated structure at 250 °C corresponds to levyne B topology of natural levyne, characterized by the statistical rupture of the T–O–T bonds of the double six-ring membered cage. However, in contrast to levyne-Ca, the fraction of broken connections reached 50% instead of 37%, and no additional structural modifications were detected up to 350 °C. At 400 °C, diffraction data pointed to the onset of the structural collapse. At this temperature, the measured unit-cell volume was 8% smaller compared to that of the RT structure. The corresponding contracted structure did not rehydrate after exposure to humid conditions for 21 days.

Impact of e-Liquid Composition, Coil Temperature, and Puff Topography on the Aerosol Chemistry of Electronic Cigarettes

E-cigarette aerosol is a complex mixture of gases and particles with a composition that is dependent on the e-liquid formulation, puffing regimen, and device operational parameters. This work investigated mainstream aerosols from a third generation device, as a function of coil temperature (315-510 °F, or 157-266 °C), puff duration (2-4 s), and the ratio of propylene glycol (PG) to vegetable glycerin (VG) in e-liquid (100:0-0:100). Targeted and untargeted analyses using liquid chromatography high-resolution mass spectrometry, gas chromatography, in situ chemical ionization mass spectrometry, and gravimetry were used for chemical characterizations. PG and VG were found to be the major constituents (>99%) in both phases of the aerosol. Most e-cigarette components were observed to be volatile or semivolatile under the conditions tested. PG was found almost entirely in the gas phase, while VG had a sizable particle component. Nicotine was only observed in the particle phase. The production of aerosol mass and carbonyl degradation products dramatically increased with higher coil temperature and puff duration, but decreased with increasing VG fraction in the e-liquid. An exception is acrolein, which increased with increasing VG. The formation of carbonyls was dominated by the heat-induced dehydration mechanism in the temperature range studied, yet radical reactions also played an important role. The findings from this study identified open questions regarding both pathways. The vaping process consumed PG significantly faster than VG under all tested conditions, suggesting that e-liquids become more enriched in VG and the exposure to acrolein significantly increases as vaping continues. It can be estimated that a 30:70 initial ratio of PG:VG in the e-liquid becomes almost entirely VG when 60-70% of e-liquid remains during the vaping process at 375 °F (191 °C). This work underscores the need for further research on the puffing lifecycle of e-cigarettes.