Effect of Poly(propylene carbonate) on Properties of Polylactic Acid-Based Composite Films.

To enrich the properties of polylactic acid (PLA)-based composite films and improve the base degradability, in this study, a certain amount of poly(propylene carbonate) (PPC) was added to PLA-based composite films, and PLA/PPC-based composite films were prepared by melt blending and hot-press molding. The effects of the introduction of PPC on the composite films were analyzed through in-depth studies on mechanical properties, water vapor and oxygen transmission rates, thermal analysis, compost degradability, and bacterial inhibition properties of the composite films. When the introduction ratio coefficient of PPC was 30%, the tensile strength of the composite film increased by 19.68%, the water vapor transmission coefficient decreased by 14.43%, and the oxygen transmission coefficient decreased by 18.31% compared to that of the composite film without PPC, the cold crystallization temperature of the composite film increased gradually from 96.9 °C to 104.8 °C, and PPC improved the crystallization ability of composite film. The degradation rate of the composite film with PPC increased significantly compared to the previous one, and the degradation rate increased with the increase in the PPC content. The degradation rate was 49.85% and 46.22% faster on average than that of the composite film without PPC when the degradation was carried out over 40 and 80 days; the composite film had certain inhibition, and the maximum diameter of the inhibition circle was 2.42 cm. This study provides a strategy for the development of PLA-based biodegradable laminates, which can promote the application of PLA-based laminates in food packaging.

Nitrogen dioxide exposure, health outcomes, and associated demographic disparities due to gas and propane combustion by U.S. stoves.

Gas and propane stoves emit nitrogen dioxide (NO2) pollution indoors, but the exposures of different U.S. demographic groups are unknown. We estimate NO2 exposure and health consequences using emissions and concentration measurements from >100 homes, a room-specific indoor air quality model, epidemiological risk parameters, and statistical sampling of housing characteristics and occupant behavior. Gas and propane stoves increase long-term NO2 exposure 4.0 parts per billion volume on average across the United States, 75% of the World Health Organization's exposure guideline. This increased exposure likely causes ~50,000 cases of current pediatric asthma from long-term NO2 exposure alone. Short-term NO2 exposure from typical gas stove use frequently exceeds both World Health Organization and U.S. Environmental Protection Agency benchmarks. People living in residences <800 ft2 in size incur four times more long-term NO2 exposure than people in residences >3000 ft2 in size; American Indian/Alaska Native and Black and Hispanic/Latino households incur 60 and 20% more NO2 exposure, respectively, than the national average.

Abiotic natural attenuation of 1,2,3-trichloropropane by natural magnetite under O2 perturbation.

1,2,3-Trichloropropane (TCP) is an emerging groundwater pollutant, but there is a lack of reported studies on the abiotic natural attenuation of TCP by iron minerals. Furthermore, perturbation by O2 is common in the shallow subsurface by both natural and artificial processes. In this study, natural magnetite was selected as the reactive iron mineral to investigate its role in the degradation of TCP under O2 perturbation. The results indicated that the mineral structural Fe(II) on magnetite reacted with dissolved oxygen to generate O2-· and HO·. Both O2-· and HO· contributed to TCP degradation, with O2-· playing a more important role. After 56 days of reaction, 66.7% of TCP was completely dechlorinated. This study revealed that higher magnetite concentrations, smaller magnetite particle sizes, and lower initial TCP concentrations favored TCP degradation. The presence of <10 mg/L natural organic matter (NOM) did not affect TCP degradation. These findings significantly advance our understanding of the abiotic natural attenuation mechanisms facilitated by iron minerals under O2 perturbation, providing crucial insights for the study of natural attenuation.

The long-chain flavodoxin FldX1 improves the biodegradation of 4-hydroxyphenylacetate and 3-hydroxyphenylacetate and counteracts the oxidative stress associated to aromatic catabolism in Paraburkholderia xenovorans.

BACKGROUND: Bacterial aromatic degradation may cause oxidative stress. The long-chain flavodoxin FldX1 of Paraburkholderia xenovorans LB400 counteracts reactive oxygen species (ROS). The aim of this study was to evaluate the protective role of FldX1 in P. xenovorans LB400 during the degradation of 4-hydroxyphenylacetate (4-HPA) and 3-hydroxyphenylacetate (3-HPA). METHODS: The functionality of FldX1 was evaluated in P. xenovorans p2-fldX1 that overexpresses FldX1. The effects of FldX1 on P. xenovorans were studied measuring growth on hydroxyphenylacetates, degradation of 4-HPA and 3-HPA, and ROS formation. The effects of hydroxyphenylacetates (HPAs) on the proteome (LC-MS/MS) and gene expression (qRT-PCR) were quantified. Bioaugmentation with strain p2-fldX1 of 4-HPA-polluted soil was assessed, measuring aromatic degradation (HPLC), 4-HPA-degrading bacteria, and plasmid stability. RESULTS: The exposure of P. xenovorans to 4-HPA increased the formation of ROS compared to 3-HPA or glucose. P. xenovorans p2-fldX1 showed an increased growth on 4-HPA and 3-HPA compared to the control strain WT-p2. Strain p2-fldX1 degraded faster 4-HPA and 3-HPA than strain WT-p2. Both WT-p2 and p2-fldX1 cells grown on 4-HPA displayed more changes in the proteome than cells grown on 3-HPA in comparison to glucose-grown cells. Several enzymes involved in ROS detoxification, including AhpC2, AhpF, AhpD3, KatA, Bcp, CpoF1, Prx1 and Prx2, were upregulated by hydroxyphenylacetates. Downregulation of organic hydroperoxide resistance (Ohr) and DpsA proteins was observed. A downregulation of the genes encoding scavenging enzymes (katE and sodB), and gstA and trxB was observed in p2-fldX1 cells, suggesting that FldX1 prevents the antioxidant response. More than 20 membrane proteins, including porins and transporters, showed changes in expression during the growth of both strains on hydroxyphenylacetates. An increased 4-HPA degradation by recombinant strain p2-fldX1 in soil microcosms was observed. In soil, the strain overexpressing the flavodoxin FldX1 showed a lower plasmid loss, compared to WT-p2 strain, suggesting that FldX1 contributes to bacterial fitness. Overall, these results suggest that recombinant strain p2-fldX1 is an attractive bacterium for its application in bioremediation processes of aromatic compounds. CONCLUSIONS: The long-chain flavodoxin FldX1 improved the capability of P. xenovorans to degrade 4-HPA in liquid culture and soil microcosms by protecting cells against the degradation-associated oxidative stress.

Poly(Propylene Carbonate)-Based Biodegradable and Environment-Friendly Materials for Biomedical Applications.

Poly(propylene carbonate) (PPC) is an emerging "carbon fixation" polymer that holds the potential to become a "biomaterial of choice" in healthcare owing to its good biocompatibility, tunable biodegradability and safe degradation products. However, the commercialization and wide application of PPC as a biomedical material are still hindered by its narrow processing temperature range, poor mechanical properties and hydrophobic nature. Over recent decades, several physical, chemical and biological modifications of PPC have been achieved by introducing biocompatible polymers, inorganic ions or small molecules, which can endow PPC with better cytocompatibility and desirable biodegradability, and thus enable various applications. Indeed, a variety of PPC-based degradable materials have been used in medical applications including medical masks, surgical gowns, drug carriers, wound dressings, implants and scaffolds. In this review, the molecular structure, catalysts for synthesis, properties and modifications of PPC are discussed. Recent biomedical applications of PPC-based biomaterials are highlighted and summarized.

Sudden death due to butane abuse - An overview.

Volatile Solvents Abuse (VSA) poses major health risks, especially for young people and those living in precarious socio-economic conditions. Such substances can in fact bring about psychoactive effects such as euphoria, and even lead to sudden death from cardiac arrhythmias, respiratory depression, myocardial infarction, laryngospasm, encephalopathy, and rhabdomyolysis. The present case report is centered around a 23-year-old man who died in prison due to inhalation of a cooker gas mixture (n-butane, propane, and isobutane) inside a plastic bag. External examination and autopsy showed non-specific signs of asphyxia associated with edema and brain swelling. Histological signs of early myocardial damage and hypoxic-ischemic injury (HII) were highlighted in the brain and cerebellum, as well as activated macrophages and anthracotic-like material in the lungs. Toxicological investigations revealed the presence of propane, isobutane and n-butane in liquids and biological samples. Besides the cardiotoxic effect, there was an asphyctic component due to the plastic bag that may have facilitated death. The assessment of cerebral HII and cardiopulmonary damage in acute cases is very important to prove death by butane inhalation. In the forensic field, it may be useful to shed more light on intoxications, deaths, and butane encephalopathies, as the latter can be mistaken for a hypoxic-ischemic encephalopathy.

Human health risk assessment of volatile organic compounds in oil-based drill cuttings of shale gas.

Waste oil-based drill cuttings contain dioxins and volatile organic compounds (VOCs), which have the potential to cause serious health effects in humans. Therefore, this paper took oil-based drill cuttings (OBDCs) as the research object and carried out the testing of VOCs and dioxins content by using GC-MS and HRGCS-HRMS and comprehensively evaluated the content, composition and distribution pattern of VOCs and dioxins and the risk to human health posed by the two pollutants in OBDCs. The results showed that the VOCs did not exceed the emission limits in ESPPI (GB 31571-2015), but it is vital to recognise that 1,2-dichloropropane has the potential to cause cancer risk, with soil and groundwater risk control values of 662.95 mg·kg-1 and 0.066 mg·kg-1, respectively. Benzene, 1,2-dichloropropane and 8 other VOCs pose a non-carcinogenic risk to humans. The levels of polychlorinated dibenzofurans (PCDFs) exceeded those of polychlorinated dibenzo-p-dioxins (PCDDs), which accounted for 95.76 percent of the total PCDD/Fs, 2,3,4,7,8-P5CDF (56.00%), 2,3,7,8-T4CDF (9.20%), 1,2,3,6,7,8-H6CDF (8.80%) and 1,2,3,7,8-P5CDF (8.00%) were the main contributing monomers. The findings of the assessment on exposure risk indicate that there is a respiratory risk to oil-based drill cuttings dioxins for adults and children exceeded the World Health Organisation (WHO) acceptable daily intake (ADI) (1-4 pgTEQ/kg/d). Finally, three aspects of solid waste pre-treatment prior to incineration, the incineration process and post incineration were used to reduce the environmental and human health risks from dioxins.

Occurrence of Rhodococcus sp. RR1 prmA and Rhodococcus jostii RHA1 prmA across microbial communities and their enumeration during 1,4-dioxane biodegradation.

1,4-Dioxane, a likely human carcinogen, is a co-contaminant at many chlorinated solvent contaminated sites. Conventional treatment technologies, such as carbon sorption or air stripping, are largely ineffective, and so many researchers have explored bioremediation for site clean-up. An important step towards this involves examining the occurrence of the functional genes associated with 1,4-dioxane biodegradation. The current research explored potential biomarkers for 1,4-dioxane in three mixed microbial communities (wetland sediment, agricultural soil, impacted site sediment) using monooxygenase targeted amplicon sequencing, followed by quantitative PCR (qPCR). A BLAST analysis of the sequencing data detected only two of the genes previously associated with 1,4-dioxane metabolism or co-metabolism, namely propane monooxygenase (prmA) from Rhodococcus jostii RHA1 and Rhodococcus sp. RR1. To investigate this further, qPCR primers and probes were designed, and the assays were used to enumerate prmA gene copies in the three communities. Gene copies of Rhodococcus RR1 prmA were detected in all three, while gene copies of Rhodococcus jostii RHA1 prmA were detected in two of the three sample types (except impacted site sediment). Further, there was a statistically significant increase in RR1 prmA gene copies in the microcosms inoculated with impacted site sediment following 1,4-dioxane biodegradation compared to the control microcosms (no 1,4-dioxane) or to the initial copy numbers before incubation. Overall, the results indicate the importance of Rhodococcus associated prmA, compared to other 1,4-dioxane degrading associated biomarkers, in three different microbial communities. Also, the newly designed qPCR assays provide a platform for others to investigate 1,4-dioxane biodegradation potential in mixed communities and should be of particular interest to those considering bioremediation as a potential 1,4-dioxane remediation approach.

K2CO3-Modified Smectites as Basic Catalysts for Glycerol Transcarbonation to Glycerol Carbonate.

A novel and cost-effective heterogeneous catalyst for glycerol carbonate production through transesterification was developed by impregnating smectite clay with K2CO3. Comprehensive structural and chemical analyses, including X-ray diffraction Analysis (XRD), Scanning Electron Microscopy (SEM)-Electron Dispersion Spectroscopy (EDS), Fourier Transform Infrared Spectroscopy (FTIR), and Brunauer-Emmett-Teller (BET) surface area analysis measurements, were employed to characterize the catalysts. Among the various catalysts prepared, the one impregnated with 40 wt% K2CO3 on smectite and calcined at 550 °C exhibited the highest catalytic activity, primarily due to its superior basicity. To enhance the efficiency of the transesterification process, several reaction parameters were optimized, including the molar ratio between propylene carbonate and glycerol reactor loading of the catalyst and reaction temperature. The highest glycerol carbonate conversion rate, approximately 77.13% ± 1.2%, was achieved using the best catalyst under the following optimal conditions: 2 wt% reactor loading, 110 °C reaction temperature, 2:1 propylene carbonate to glycerol molar ratio, and 6h reaction duration. Furthermore, both the raw clay and the best calcined K2CO3-impregnated catalysts demonstrated remarkable stability, maintaining their high activity for up to four consecutive reaction cycles. Finally, a kinetic analysis was performed using kinetic data from several runs employing raw clay and the most active K2CO3-modified clay at different temperatures, observing that a simple reversible second-order potential kinetic model of the quasi-homogeneous type fits perfectly to such data in diverse temperature ranges.

Nitrate-driven anaerobic oxidation of ethane and butane by bacteria.

The short-chain gaseous alkanes (ethane, propane, and butane; SCGAs) are important components of natural gas, yet their fate in environmental systems is poorly understood. Microbially mediated anaerobic oxidation of SCGAs coupled to nitrate reduction has been demonstrated for propane, but is yet to be shown for ethane or butane-despite being energetically feasible. Here we report two independent bacterial enrichments performing anaerobic ethane and butane oxidation, respectively, coupled to nitrate reduction to dinitrogen gas and ammonium. Isotopic 13C- and 15N-labelling experiments, mass and electron balance tests, and metabolite and meta-omics analyses collectively reveal that the recently described propane-oxidizing "Candidatus Alkanivorans nitratireducens" was also responsible for nitrate-dependent anaerobic oxidation of the SCGAs in both these enrichments. The complete genome of this species encodes alkylsuccinate synthase genes for the activation of ethane/butane via fumarate addition. Further substrate range tests confirm that "Ca. A. nitratireducens" is metabolically versatile, being able to degrade ethane, propane, and butane under anoxic conditions. Moreover, our study proves nitrate as an additional electron sink for ethane and butane in anaerobic environments, and for the first time demonstrates the use of the fumarate addition pathway in anaerobic ethane oxidation. These findings contribute to our understanding of microbial metabolism of SCGAs in anaerobic environments.

Optimizing the Ion Conductivity and Mechanical Stability of Polymer Electrolyte Membranes Designed for Use in Lithium Ion Batteries: Combining Imidazolium-Containing Poly(ionic liquids) and Poly(propylene carbonate).

State-of-the-art Li batteries suffer from serious safety hazards caused by the reactivity of lithium and the flammable nature of liquid electrolytes. This work develops highly efficient solid-state electrolytes consisting of imidazolium-containing polyionic liquids (PILs) and lithium bis(trifluoromethane sulfonyl)imide (LiTFSI). By employing PIL/LiTFSI electrolyte membranes blended with poly(propylene carbonate) (PPC), we addressed the problem of combining ionic conductivity and mechanical properties in one material. It was found that PPC acts as a mechanically reinforcing component that does not reduce but even enhances the ionic conductivity. While pure PILs are liquids, the tricomponent PPC/PIL/LiTFSI blends are rubber-like materials with a Young's modulus in the range of 100 MPa. The high mechanical strength of the material enables fabrication of mechanically robust free-standing membranes. The tricomponent PPC/PIL/LiTFSI membranes have an ionic conductivity of 10-6 S·cm-1 at room temperature, exhibiting conductivity that is two orders of magnitude greater than bicomponent PPC/LiTFSI membranes. At 60 °C, the conductivity of PPC/PIL/LiTFSI membranes increases to 10-5 S·cm-1 and further increases to 10-3 S·cm-1 in the presence of plasticizers. Cyclic voltammetry measurements reveal good electrochemical stability of the tricomponent PIL/PPC/LiTFSI membrane that potentially ranges from 0 to 4.5 V vs. Li/Li+. The mechanically reinforced membranes developed in this work are promising electrolytes for potential applications in solid-state batteries.

Analytical methods for detecting butane, propane, and their metabolites in biological samples: Implications for inhalant abuse detection.

Worldwide, various inhalants are widely abused for recreational purposes, with butane and propane emerging as among the most commonly misused volatile substances, posing a significant risk of sudden death. The rapid elimination and oxidation of these highly volatile compounds upon inhalation necessitate the identification of butane and propane along with their metabolites in biological samples. Hence, the primary objective of this study is twofold: firstly, to establish a method for analyzing butane, propane, and metabolites, and secondly, to demonstrate the detection window and exposure indicators associated with the inhalation of butane and propane. In pursuit of this objective, we developed analytical methods for the determination of isobutane, n-butane, propane, and their nine metabolites in both blood and urine. Headspace-gas chromatography-mass spectrometry (GC-MS) and solid-phase microextraction-GC-MS were employed for the analyses, demonstrating acceptable precision and accuracy. An animal study revealed that isobutane and n-butane were only detectable below the limit of quantification (LOQ) in rat blood 5 min after exposure. Meanwhile, the three major metabolites-2-methyl-2-propanol, 2-butanol, and 2-butanone-were observed 5 min after exposure but persisted in rat urine even 5 h post-exposure. Additionally, human urine samples identified other metabolites, including acetone, acetoin, and 2,3-butanediol isomers. The presence of specific metabolites corresponding to each inhalant confirmed the abuse of butane and propane. This comprehensive approach provides valuable insights into the detection and assessment of inhalation to these volatile substances.

Potential molecular mechanism of reuterin on the inhibition of Aspergillus flavus conidial germination: An in silico study.

Reuterin is a natural antifungal agent derived from certain strains of Limosilactobacillus reuteri. Our previous study revealed that 6 mM reuterin inhibited completely the conidial germination of aflatoxigenic Aspergillus flavus. This study investigated the potential molecular mechanism of reuterin in inhibiting A. flavus conidial germination, which was pre-assumed that it correlated to the inhibition of some essential enzyme activity involved in conidial germination, specifically 1,3-ß-glucan synthase, chitin synthase, and catalases (catalase, bifunctional catalase-peroxidase, and spore-specific catalase). The complex of 1,3-ß-glucan synthase and chitin synthase with reuterin had a lower binding affinity than that with the substrate. Conversely, the complex of catalases with reuterin had a higher binding affinity than that with the substrate. It was suggested that 1,3-ß-glucan synthase and chitin synthase tended to bind the substrate rather than bind reuterin. In contrast, catalases tended to bind reuterin rather than bind the substrate. Therefore, reuterin could be a potential inhibitor of catalases but may not be an inhibitor of 1,3-ß-glucan synthase and chitin synthase. In this in silico study, we predicted that the potential molecular mechanism of reuterin in inhibiting A. flavus conidial germination was due to the inhibition of catalases activities by competitively binding to the enzymes active sites, thus resulting in the accumulation of reactive oxygen species in cells, leading to cells damage. PRACTICAL APPLICATION: This in silico study revealed that reuterin is a potential inhibitor of catalases in A. flavus, thereby interfering with the antioxidant system during conidial germination. This finding shows that reuterin can be used as an antifungal agent in food or agricultural products, inhibiting conidial germination completely.

Monte Carlo model for ion mobility and diffusion for characteristic electric fields in nanodosimetry.

The quantification of the effects of space radiation for manned spaceflight can be approximated by nanodosimetric measurements. For the development of nanodosimetric detectors, a Monte Carlo model for ion mobility and diffusion for characteristic electric fields is presented. This model can be used to describe the interactions of ions in their parent gas based solely on commonly known input parameters, such as the ionization potential, kinetic diameter, molar mass, and polarizability of the gas. A model for approximating the resonant charge exchange cross section has been proposed, requiring only the ionization energy and mass of the parent gas as input parameters. The method proposed in this work was tested against experimental drift velocity data for a wide range of gases (helium, neon, nitrogen, argon, krypton, carbon monoxide, carbon dioxide, oxygen, propane). The transverse diffusion coefficients were compared to experimental values for helium, nitrogen, neon, argon, and propane gas. With the Monte Carlo code and resonant charge exchange cross section approximation model presented in this work, it is now possible to calculate an estimate of the drift velocities, transverse diffusion, and thus the ion mobility of ions in their parent gas. This is essential for further nanodosimetric detector development, as those parameters are often not well known for the gas mixtures used in nanodosimetry.

Plasmid-encoded toxin defence mediates mutualistic microbial interactions.

Gut environments harbour dense microbial ecosystems in which plasmids are widely distributed. Plasmids facilitate the exchange of genetic material among microorganisms while enabling the transfer of a diverse array of accessory functions. However, their precise impact on microbial community composition and function remains largely unexplored. Here we identify a prevalent bacterial toxin and a plasmid-encoded resistance mechanism that mediates the interaction between Lactobacilli and Enterococci. This plasmid is widespread across ecosystems, including the rumen and human gut microbiota. Biochemical characterization of the plasmid revealed a defence mechanism against reuterin, a toxin produced by various gut microbes, such as Limosilactobacillus reuteri. Using a targeted metabolomic approach, we find reuterin to be prevalent across rumen ecosystems with impacts on microbial community structure. Enterococcus strains carrying the protective plasmid were isolated and their interactions with L. reuteri, the toxin producer, were studied in vitro. Interestingly, we found that by conferring resistance against reuterin, the plasmid mediates metabolic exchange between the defending and the attacking microbial species, resulting in a beneficial relationship or mutualism. Hence, we reveal here an ecological role for a plasmid-coded defence system in mediating a beneficial interaction.

Influence of the Charge Ratio of Guanine-Quadruplex Structure-Based CpG Oligodeoxynucleotides and Cationic DOTAP Liposomes on Cytokine Induction Profiles.

Cationic liposomes, specifically 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP) liposomes, serve as successful carriers for guanine-quadruplex (G4) structure-based cytosine-guanine oligodeoxynucleotides (CpG ODNs). The combined benefits of CpG ODNs forming a G4 structure and a non-viral vector carrier endow the ensuing complex with promising adjuvant properties. Although G4-CpG ODN-DOTAP complexes show a higher immunostimulatory effect than naked G4-CpG ODNs, the effects of the complex composition, especially charge ratios, on the production of the pro-inflammatory cytokines interleukin (IL)-6 and interferon (IFN)-α remain unclear. Here, we examined whether charge ratios drive the bifurcation of cytokine inductions in human peripheral blood mononuclear cells. Linear CpG ODN-DOTAP liposome complexes formed micrometer-sized positively charged agglomerates; G4-CpG ODN-DOTAP liposome complexes with low charge ratios (0.5 and 1.5) formed ~250 nm-sized negatively charged complexes. Notably, low-charge-ratio (0.5 and 1.5) complexes induced significantly higher IL-6 and IFN-α levels simultaneously than high-charge-ratio (2 and 2.5) complexes. Moreover, confocal microscopy indicated a positive correlation between the cellular uptake of the complex and amount of cytokine induced. The observed effects of charge ratios on complex size, surface charge, and affinity for factors that modify cellular-uptake, intracellular-activity, and cytokine-production efficiency highlight the importance of a rational complex design for delivering and controlling G4-CpG ODN activity.

Long short-term memory based quasi-targeted lipidomics reveals propane-1,2-diol expediting the digestion of lipids via mediating the α-helices to a random curl or ß folding of lipase.

Scandal of detecting 1,2-propanediol (PD) in milk brought a crisis to the trust of consumers in dairy industry, and investigations focused effect of PD on digestive behavior of milk were still restricted. Long short-term memory amalgamated to quasi-targeted lipidomics was applied to monitor dynamics changes of lipids during digestion and the pseudo-first-order kinetic model elucidated that PD elevated the digestibility of lipid with the degradation rate (S-1) ranged from 4440.31 to 5665.59 and mediated the transition of α-helices (26.46% to 19.07% of pancreatic lipase and 29.89% to 23.37% of gastric lipase) covering active center in lipase to random curl (48.25% to 51.17% of pancreatic lipase and 41.58% to 44.57% of gastric lipase) and ß folding (9.14% to 4.67% of pancreatic lipase and 6.52% to 10.05% of gastric lipase), ultimately upregulating the lipase activity and further intervening lipid nutrients utilization in milk. This study provided a critical insight about the impact of PD contamination at trace concentrations on the nutritional value of milk fat during digestion.

Carbon Monoxide Levels Produced by Propane/Isobutane Canister Stoves inside a Tent.

INTRODUCTION: Improper use of camp stoves in enclosed spaces has resulted in fatalities from carbon monoxide (CO) poisoning. Prior research has focused on the CO output of stoves burning white gas, unleaded gas, or kerosene. Stoves burning an isobutane/propane fuel have not been investigated and are the focus of this study. METHODS: Three stoves utilizing isobutane/propane fuel were used to heat a pot of water inside a 3-season tent under controlled settings. Multiple runs with each stove were performed, and CO measurements, in parts per million (ppm), were recorded at 1-min intervals for a total of 15 min using a RAE Systems gas monitor. Data are reported as mean with SD. Repeated measures analysis of variance was utilized to examine changes over time. Statistical significance was set at P<0.05. RESULTS: There was a statistically significant main effect of time and CO level, F (14, 168)=7.6, P<0.001. There was a statistically significant difference between-subjects effect of stove group F (2, 12)=8.6, P=0.005, indicating that CO levels were different depending on the stove. Tukey's post-hoc analyses revealed that stove A had the highest CO levels. The average level of stove A was statistically significantly higher than that of stove B and stove C, with a mean CO level difference of 79 ppm (95% CI, 3-156), P=0.043 and 117 ppm (95% CI, 40-194), P=0.004, respectively. CONCLUSIONS: Stoves utilizing isobutane/propane fuel can produce unsafe CO levels and should not be used in enclosed spaces.

Abatement of photochemical smog precursors through complete hydrocarbon oxidation over commercial Pd catalysts under fuel-lean conditions with NO promoting effect.

Currently, severe environmental issues have led to a great transition in the automotive industry from internal combustion engine vehicles to electric vehicles, but this transition will take time more than 10 years, which still requires the use of internal combustion engine vehicles. However, these vehicles emit a significant amount of hydrocarbons, in addition to nitrogen oxides (NOx), due to incomplete fuel combustion. They contribute to the formation of photochemical smog when they react with NOx in the presence of sunlight. To effectively remove these hydrocarbons from the exhaust gas of turbo-gasoline engines or diesel engines, we investigated the abatement of propane and iso-pentane, two typical hydrocarbons. In particular, we studied commercial Pd catalysts and revealed how the Pd loading and aging process simulating 4k and 100k mileage affected hydrocarbon abatement abilities, and their phases were identified using characterization technique, including CO chemisorption, X-ray diffraction (XRD), and high-resolution transmission electron microscopy (HR-TEM). We also suggested the reaction pathway for the complete oxidation of propane over Pd catalyst based on the reaction orders of propane and oxygen: Propane adsorbs on O atoms of PdO, and the kinetically relevant C-H bond cleavage step occurs by the interaction with abundant neighboring O atoms of PdO. Finally, the propane and iso-pentane abatement ability of the Pd catalyst aged for 100k mileage were evaluated under realistic exhaust gas conditions, and the effect of each gas component in the realistic exhaust gas was identified; water inhibits the catalytic reaction of hydrocarbons by occupying the active sites, whereas NO catalyzes the hydrocarbon oxidation reaction by either changing the reaction pathway or active sites under fuel-lean conditions. These findings enable us to effectively reduce environmental pollution and facilitate a smoother transition from internal combustion engine vehicles to electric vehicles.

A multicomponent propane monooxygenase catalyzes the initial degradation of methyl tert-butyl ether in Mycobacterium vaccae JOB5.

Methyl tert-butyl ether (MTBE) has been recognized as a groundwater contaminant due to its widespread distribution and potential threat to human health. The limited understanding of the enzymes catalyzing MTBE degradation restricts their application in MTBE bioremediation. In this study, an MTBE-degrading soluble di-iron monooxygenase that clusters phylogenetically with a known propane monooxygenase (PRM) encoded by the prmABCD gene cluster was identified and functionally characterized, revealing their role in MTBE metabolism by Mycobacterium vaccae JOB5. Transcriptome analysis demonstrated that the expression of prmABCD was upregulated when JOB5 was induced by MTBE. Escherichia coli Rosetta heterologously expressing prmABCD from JOB5 could transform MTBE, indicating that the PRM of JOB5 is capable of the initial degradation of MTBE. The loss of the gene encoding the oxygenase α-subunit or ß-subunit, the coupling protein, or the reductase disrupted MTBE transformation by the recombinant E. coli Rosetta. In addition, the catalytic capacity of PRM is likely affected by residue G95 in the active site pocket and residues I84, P165, A269, and V270 in the substrate tunnel structure. Mutation of amino acids in the active site and substrate tunnel resulted in inefficiency or inactivation of MTBE degradation, and the activity in 1,4-dioxane (1,4-D) degradation was diminished less than that in MTBE degradation.IMPORTANCEMulticomponent monooxygenases catalyzing the initial hydroxylation of MTBE are important in MTBE biodegradation. Previous studies of MTBE degradation enzymes have focused on P450s, alkane monooxygenase and MTBE monooxygenase, but the vital role of soluble di-iron monooxygenases has rarely been reported. In this study, we deciphered the essential catalytic role of a PRM and revealed the key residues of the PRM in MTBE metabolism. Our findings provide new insight into the MTBE-degrading gene cluster and enzymes in bacteria. This characterization of the PRM associated with MTBE degradation expands our understanding of MTBE-degrading gene diversity and provides a novel candidate enzyme for the bioremediation of MTBE-contaminated sites.