Search Results (11)

Methylamines are present in numerous organisms and microorganisms capable of de novo trimethylamine (TMA) production are widely distributed, including microalgae. However, such compounds may hamper the application of microalgae biomass in commercially interesting products, such as food and feed products, due to the strong fishy smell. In the present study, several bacteria able to degrade TMA were isolated. Among them, a Staphylococcus saprophyticus strain was found particularly suitable to degrade TMA. After finding the best culture conditions, a bioprocess system was developed allowing the degradation of TMA from microalgae in a reactor by S. saprophyticus cells present in a second reactor without direct contact with media from both reactors. The system was found to be limited by TMA transfer through the gas phase, with the cells being able to degrade all available TMA. Full article

A sudden increase in polyurethane (PU) production necessitates viable recycling methods for the waste generated. PU is one of the most important plastic materials with a wide range of applications; however, the stability of the urethane linkage is a major issue in chemical recycling. In this work, termination reactions of a model urethane molecule, namely methyl N-phenyl carbamate (MPCate), are investigated using G3MP2B3 composite quantum chemical method. Our main goal was to gain insights into the energetic profile of urethane bond termination and find an applicable chemical recycling method. Hydrogenation, hydrolysis, methanolysis, peroxidation, glycolysis, ammonolysis, reduction with methylamine and termination by dimethyl phosphite were explored in both gas and condensed phases. Out of these chemicals, degradation by H₂, H₂O₂ and CH₃NH₂ revealed promising results with lower activation barriers and exergonic pathways, especially in water solvation. Implementing these effective PU recycling methods can also have significant economic benefits since the obtained products from the reactions are industrially relevant substances. For example, aniline and dimethyl carbonate could be reusable in polymer technologies serving as potential methods for circular economy. As further potential transformations, several ionizations of MPCate were also examined including electron capture and detachment, protonation/deprotonation and reaction with OH⁻. Alkaline digestion against the model urethane MPCate was found to be promising due to the relatively low activation energy. In an ideal case, the transformation of the urethane bond could be an enzymatic process; therefore, potential enzymes, such as lipoxygenase, were also considered for the catalysis of peroxidation, and lipases for methanolysis. Full article

N-nitrosodimethylamine (NDMA), as an emerging nitrogenous disinfection byproduct, is strictly controlled by multiple countries due to its high toxicity in drinking water. Advanced reduction processes (ARPs) are a new type of water treatment technology that can generate highly reactive reducing radicals and make environmental contaminants degrade rapidly and innocuously. In this study, a systematic investigation on the kinetics of the NDMA degradation via the chosen UV/sulfite ARP and the impacts of some key parameters of reaction system was conducted. The results indicated that the UV/sulfite ARP was an efficient and energy saving method for the reductive degradation of NDMA. A total of 94.40% of NDMA was removed using the UV/sulfite ARP, while only 45.48% of NDMA was removed via direct UV photolysis under the same reaction conditions. The degradation of NDMA via the UV/sulfite ARP followed pseudo-first-order kinetics. Increasing both the UV light intensity and sulfite dosage led to a proportional increase in the NDMA removal efficiency. The alkaline condition favored the degradation of NDMA, with the removal efficiency increasing from 21.57% to 66.79% within the initial 5 min of the reaction when the pH increased from 3 to 11. The presence of dissolved oxygen substantially decreased the removal efficiency of NDMA due to the formation of oxidizing superoxide radicals, which competed with NDMA by capturing the reducing active radicals during the reaction. An analysis of the degradation products indicated that several refractory intermediates such as dimethylamine, methylamine and nitrite were completely decomposed via the UV/sulfite ARP, and the final degradation products were formate, ammonia and nitrogen. Full article

General hot-plate heating is used to form a crystal structure of films; however, how to achieve a homogeneous and regulated crystal formation will be a crucial challenge in the future. In this study, based on perovskite-series materials, organic methylamine lead trioxide (MAPbI₃) films doped with inorganic lead iodide (CsPbI₃) quantum dots (QDs) are treated using the rapid thermal annealing (RTA) process in argon gas to break the crystallization barrier. These RTA-treated perovskite quantum dot (PQD) films at various temperatures of 100–160 °C are detected using X-ray diffraction, X-ray spectroscopy, and absorbance measurements to investigate their structural and optical properties as well as their binding states. The experimental results demonstrate that the PQD film annealed at 120 °C has optimized characteristics, revealing better crystallinity and the lowest content of oxygen atoms (31.4%) and C-O-C bonding (20.1%). A too-high RTA temperature, more than 140 °C, causes severe degradation with the existence of PbI₂. A proper RTA process, an alternative to normal heating and annealing, can effectively inhibit the occurrence of degradation and even usefully improve the performance of PQD films. Full article

Volatile organic compounds (VOCs) are an important source of air pollution, harmful to human health and the environment, and important precursors of secondary organic aerosols, O₃ and photochemical smog. This study focused on the low-temperature catalytic oxidation and degradation of benzene, dichloroethane, methanethiol, methanol and methylamine by ozone. Benzene was used as a model compound, and a molecular sieve was selected as a catalyst carrier to prepare a series of supported active metal catalysts by impregnation. The effects of ozone on the catalytic oxidation of VOCs and catalysts’ activity were studied. Taking benzene as a model compound, low-temperature ozone catalytic oxidation was conducted to explore the influence of the catalyst carrier, the active metal and the precious metal Pt on the catalytic degradation of benzene. The optimal catalyst appeared to be 0.75%Pt–10%Fe/HZSM(200). The catalytic activity and formation of the by-products methylamine, methanethiol, methanol, dichloroethane and benzene over 0.75%Pt–10%Fe/HZSM(200) were investigated. The structure, oxygen vacancy, surface properties and surface acidity of the catalysts were investigated. XRD, TEM, XPS, H₂-TPR, EPR, CO₂-TPD, BET, C₆H₆-TPD and Py-IR were combined to establish the correlation between the surface properties of the catalysts and the degradation activity. Full article

In this study, the inorganic perovskite cesium lead triiodide (CsPbI₃) quantum dots (QDs) produced by hot-injection method were added into the hybrid perovskite methylamine lead triiodide (CH₃NH₃PbI₃; MAPbI₃) to form composite perovskite film. It is not easy for argon (Ar) to react with perovskite. Therefore, argon plasma was used to optimize the properties of the surface. However, methylamine lead triiodide molecular will be degraded by excessive wattage. Therefore, the influence of plasma power acting on composite perovskite film was investigated. The experimental results show that the light absorption capacity can be increased by argon plasma power of 140 watt (W) acting on the surface of films because organic impurities are removed and surface morphology of film is changed. Full article

This study aimed to evaluate the effects of processing methods on the content of biogenic amines in Zijuan tea by using derivatization and hot trichloroacetic acid extraction with HPLC-UV. The results showed that the most abundant biogenic amine in the original leaves was butylamine, followed by ethylamine, methylamine, 1,7-diaminoheptane, histamine, tyramine, and 2-phenethylamine. However, during the process of producing green tea, white tea, and black tea, the content of ethylamine increased sharply, which directly led to their total contents of biogenic amines increasing by 184.4%, 169.3%, and 178.7% compared with that of the original leaves, respectively. Unexpectedly, the contents of methylamine, ethylamine, butylamine, and tyramine in dark tea were significantly reduced compared with those of the original leaves. Accordingly, the total content of biogenic amines in dark tea was only 161.19 μg/g, a reduction of 47.2% compared with that of the original leaves, indicating that the pile-fermentation process could significantly degrade the biogenic amines present in dark tea. Full article

Many cold-acclimated insects accumulate high concentrations of low molecular weight cryoprotectants (CPs) in order to tolerate low subzero temperatures or internal freezing. The sources from which carbon skeletons for CP biosynthesis are driven, and the metabolic reprogramming linked to cold acclimation, are not sufficiently understood. Here we aim to resolve the metabolism of putative CPs by mapping relative changes in concentration of 56 metabolites and expression of 95 relevant genes as larvae of the drosophilid fly, Chymomyza costata transition from a freeze sensitive to a freeze tolerant phenotype during gradual cold acclimation. We found that C. costata larvae may directly assimilate amino acids proline and glutamate from diet to acquire at least half of their large proline stocks (up to 55 µg per average 2 mg larva). Metabolic conversion of internal glutamine reserves that build up in early diapause may explain the second half of proline accumulation, while the metabolic conversion of ornithine and the degradation of larval collagens and other proteins might be two additional minor sources. Next, we confirm that glycogen reserves represent the major source of glucose units for trehalose synthesis and accumulation (up to 27 µg per larva), while the diet may serve as an additional source. Finally, we suggest that interconversions of phospholipids may release accumulated glycero-phosphocholine (GPC) and -ethanolamine (GPE). Choline is a source of accumulated methylamines: glycine-betaine and sarcosine. The sum of methylamines together with GPE and GPC represents approximately 2 µg per larva. In conclusion, we found that food ingestion may be an important source of carbon skeletons for direct assimilation of, and/or metabolic conversions to, CPs in a diapausing and cold-acclimated insect. So far, the cold-acclimation- linked accumulation of CPs in insects was considered to be sourced mainly from internal macromolecular reserves. Full article

Bacteria belonging to the genus Aminobacter are metabolically versatile organisms thriving in both natural and anthropized terrestrial environments. To date, the taxonomy of this genus is poorly defined due to the unavailability of the genomic sequence of A. anthyllidis LMG 26462^T and the presence of unclassified Aminobacter strains. Here, we determined the genome sequence of A. anthyllidis LMG 26462^T and performed phylogenomic, average nucleotide identity and digital DNA-DNA hybridization analyses of 17 members of genus Aminobacter. Our results indicate that 16S rRNA-based phylogeny does not provide sufficient species-level discrimination, since most of the unclassified Aminobacter strains belong to valid Aminobacter species or are putative new species. Since some members of the genus Aminobacter can utilize certain C1 compounds, such as methylamines and methyl halides, a comparative genomic analysis was performed to characterize the genetic basis of some degradative/assimilative pathways in the whole genus. Our findings suggest that all Aminobacter species are heterotrophic methylotrophs able to generate the methylene tetrahydrofolate intermediate through multiple oxidative pathways of C1 compounds and convey it in the serine cycle. Moreover, all Aminobacter species carry genes implicated in the degradation of phosphonates via the C-P lyase pathway, whereas only A. anthyllidis LMG 26462^T contains a symbiosis island implicated in nodulation and nitrogen fixation. Full article

A model for the survival of the amino acid content in micrometeorites and its possible transformations upon atmospheric entry is described. Since any organic species released in the atmosphere at high altitudes would exhibit a limited lifetime with respect to the typical timescale for atmospheric mixing (due to the substantial radiation field of the early Sun), only the organic content inside the meteorites could have contributed to prebiotic chemistry. It is thus important to determine both the amino acid loss from meteorites, due to both degassing and chemical degradation, and the extent of the chemical transformation of amino acids subjected to the increased temperature due to friction with the atmosphere. According to the interplay between the potential energy barrier and the pre-exponential factor in rate coefficients, either diffusion or chemical processing might be the dominant process following the rising temperature upon atmospheric entry. The possibility of the elimination of water from glycine to form aminoketene, or ${\mathrm{CO}}_2$ to form methylamine, ultimately driven by gravitational energy, was examined along with the more conventional formation of a peptide bond between two glycine units to afford Gly–Gly. While retention, degassing, and decarboxylation are the fastest processes, each dominating in different ranges of the initial velocity and radius, the formation of either Gly–Gly from bimolecular water elimination or aminoketene from unimolecular water elimination appears to be negligible. Full article

The present study is an investigation on the kinetics of dimethoate biodegradation and an estimation of residual dimethoate in bacterial culture by spectrophotometry. The methylene chloride extract of the culture medium was used for determination of dimethoate through its reaction with 1 chloro-2, 4 dinitrobenzene to produce methylamine whose absorbance at 505 nm gave an estimation of dimethoate content. The dimethoate standard curve follows Beer’s law at 505 nm with a slope of 0.0129 absorbance units per µg/mL. The regression equation relating concentration of dimethoate (x) with the absorbance is (y): y = 0.037 + 0.0129x. The amount of residual dimethoate after 7 days were 0, 4, 17, 28 and 29 µg/mL; the rate constants were 0.775, 0.305, 0.225, 0.167 and 0.127 each per day, and the efficiency of dimethoate degradation were 100%, 96%, 83%, 72% and 71%, for Bacillus licheniformis, Pseudomonas aeruginosa, Aeromonas hydrophila, Proteus mirabilis and Bacillus pumilus respectively. Dimethoate remediation could be attained through bacterial metabolism of the pesticide and colorimetric analysis might be useful in the estimation of dimethoate within a detection limit of 5–100 µg/mL. Full article