Frontiers in Microbiology
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2022
·
IF 6.064
Chen Yan,Zhou Ning,Chen Xueman,Wei Guoguang,Zhang Alei,Chen Kequan,Ouyang Pingkai
In this study, a gene encoding β-N-acetylglucosaminidase, designated NAGaseA, was cloned from Chitinibacter sp. GC72 and subsequently functional expressed in Escherichia coli BL21 (DE3). NAGaseA contains a glycoside hydrolase family 20 catalytic domain that shows low identity with the corresponding domain of the well-characterized NAGases. The recombinant NAGaseA had a molecular mass of 92 kDa. Biochemical characterization of the purified NAGaseA revealed that the optimal reaction condition was at 40°C and pH 6.5, and exhibited great pH stability in the range of pH 6.5–9.5. The Vmax, Km, kcat, and kcat/Km of NAGaseA toward p-nitrophenyl-N-acetyl glucosaminide (pNP-GlcNAc) were 3333.33 μmol min–1 l–1, 39.99 μmol l–1, 4667.07 s–1, and 116.71 ml μmol–1 s–1, respectively. Analysis of the hydrolysis products of N-acetyl chitin oligosaccharides (N-Acetyl COSs) indicated that NAGaseA was capable of converting N-acetyl COSs ((GlcNAc)2–(GlcNAc)6) into GlcNAc with hydrolysis ability order: (GlcNAc)2 > (GlcNAc)3 > (GlcNAc)4 > (GlcNAc)5 > (GlcNAc)6. Moreover, NAGaseA could generate (GlcNAc)3–(GlcNAc)6 from (GlcNAc)2–(GlcNAc)5, respectively. These results showed that NAGaseA is a multifunctional NAGase with transglycosylation activity. In addition, significantly synergistic action was observed between NAGaseA and other sources of chitinases during hydrolysis of colloid chitin. Finally, 0.759, 0.481, and 0.986 g/l of GlcNAc with a purity of 96% were obtained using three different chitinase combinations, which were 1.61-, 2.36-, and 2.69-fold that of the GlcNAc production using the single chitinase. This observation indicated that NAGaseA could be a potential candidate enzyme in commercial GlcNAc production.
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Journal of the Taiwan Institute of Chemical Engineers
·
2022
·
IF 5.477
Binxiong Guang,Yiwei Zhang,Yahui Xiao,Miaojun Su,Xiying Li,Yong Liu
Background It is of great significance but still a challenge in the chemical industry to develop high-efficient heterogeneous catalysts for selective oxidation of styrene into benzaldehyde with molecular oxygen. Methods Fe 3 C nanoparticles confined in N-doped carbons (Fe 3 C/NC) were prepared using Fe 3+ coordinated N-bearing ionic liquids as precursors and melamine as nitrogen source and template, followed by pyrolysis at 900 °C under N 2 atmosphere. The physicochemical properties of the as-prepared Fe 3 C/NC catalyst were analyzed by FT-IR, TG, BET, TEM, XRD, Raman and XPS, respectively, and further employed as novel heterogeneous catalyst for selective oxidation of styrene into benzaldehyde with molecular oxygen. Significant findings The results showed that the Fe 3 C nanoparticles were formed and uniformly embedded into the N-doped carbon matrix, which were confirmed to be the active sites for styrene oxidation. Moreover, the 5 % Fe 3 C/NC catalyst possessed high surface area and dominant mesoporous structure, which could expose more accessible active sites and facilitate mass transfer. As a result, the 5 % Fe 3 C/NC catalyst exhibited superior catalytic performance for styrene oxidation into benzaldehyde with the appropriate styrene conversion of 58.8 % and selectivity to benzaldehyde of 64.1 % as well as no significant activity and selectivity loss after reused at least five times.
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ACS Omega
·
2023
·
IF 4.1
Wanru Gao,Yuping Li,Yunping Zhoujin,Qun Zeng,Liwen Fang,Sean Parkin,Tonglei Li,Shigang Ruan,Sihui Long
Four 2-hydroxy-N-alkyl-N-phenyl-nicotinamides (1–4) were synthesized, and their crystal structures were analyzed to investigate the effect of substitution on their crystal packing of N-phenyl-2-hydroxynicotinanilides. In these compounds, substituents were introduced on the amide N, leading to a peptoid-like structure. One solvent-free form and two hydrates were harvested for compound 1, and one anhydrous form and one hydrate were obtained for compound 2. Polymorphism was observed in compounds 3 and 4. The molecules were found to be in the keto form rather than the enol tautomer. Because of steric effects, the molecules took on an E configuration, leading to a hairpin-like geometry. A lactam–lactam dimer synthon was formed in all solvent-free structures, and a tetramer motif was observed for the first time. Dehydration of the two hydrates of 1 and the hydrate of 2 led to their respective solvent-free form. Phase transition between the polymorphs was revealed in compound 3. Theoretical calculations, including conformational energy evaluation, hydrate forming propensity assessment, and lattice energy appraisal, were performed to provide a reasonable explanation for the keto tautomer and the formation of the hydrates of compound 1.
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JOURNAL OF APPLIED POLYMER SCIENCE
·
2021
·Vol. 138
·期 37
·50949
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IF 3.125
Fan Kong,Xueli Jia,Shuting Zhang,Mengqi Lin,Yu Cheng
We have synthesized an amphiphilic block copolymer poly(N-isopropylacrylamide)- b -poly(N-vinylcarbazole) containing 1,8-naphthalimide and spirolactam rhodamine 6G moieties via reversible addition-fragmentation chain transfer radical polymerization. The photoluminescence (PL) spectrum of the poly(N-vinylcarbazole) block well matches the absorption spectrum of the 1,8-naphthalimide moiety and the enhanced emission with a peak at 510 nm from the 1,8-naphthalimide moiety is found in the block copolymer film for excitation at 330 nm. The 560-nm emission from the rhodamine 6G moiety is observed as the block copolymer film sprayed by Britton-Robinson (B-R) buffers or Fe 3+ aqueous solutions for excitation at 330 and 400 nm. The PL intensity at 560 nm is markedly increased for the pH value of the B-R buffer lower than 3.0 or the Fe 3+ concentration in water higher than 5 × 10 −4 M. The 560-nm PL intensity is much higher for the block copolymer film photoexcited at 330 nm than that photoexcited at 400 nm due to double-step resonance energy transfer. The PL intensity ratio of 560 to 510 nm (I 560 /I 510 ) is dependent on the resonance energy transfer from 1,8-naphthalimide to rhodamine 6G, which is sensitive to the concentrations of H + and Fe 3+ ions in water.
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JOURNAL OF CHEMICAL AND ENGINEERING DATA
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2020
·
IF 2.369
Guang Yang,Jianqiang Zhang,Suhua Yu,Chunjuan Huang,Xin Song,Renjie Xu
Water as an auxiliary solvent is added to various alcohol solvents (methanol, ethanol, ethylene glycol (EG)) and N,N-dimethylformamide (DMF) to form a variety of liquid mixtures, which are divided into different types according to different proportions. Starting from pure water, 0.1 mass fraction of organic solvents is added at a time, until the ratio of organic solvent is 1. The above-mentioned liquid mixtures are used as solvents to dissolve rimsulfuron at 278.15–323.15 K under 101.1 kPa by means of the isothermal static technique. Considering that there are many factors that change the experimental results, this experiment mainly selected temperature and water content, two factors, as the main independent variables. From the point of view of temperature, it changes from a low value to a high value, so it is obvious that the solute mole fraction also follows its footsteps. Unlike the temperature, as the organic solvent is continuously diluted by water, the solute solubility changes in the opposite direction to the water content. By controlling the variable method to ensure that the above two variables remain unchanged, DMF has the best dispersion ability for all of the selected solvents to dissolve rimsulfuron. The dissolution strength of the selected solvents at 323.15 K obeyed the following ascending sequence: EG (3.192 × 10–5) < ethanol (8.497 × 10–5) < methanol (9.849 × 10–5) < DMF (2.622 × 10–4). We employed Jouyban–Acree, van’t Hoff–Jouyban–Acree, and a combination of the Apelblat–Jouyban–Acree model to calculate solubility values of rimsulfuron. Results of relative average deviation (RAD) and root-mean-square deviation (RMSD) from the van’t Hoff–Jouyban–Acree model were 2.11% and 1.50 × 10–6, respectively. For drugs with poor water solubility and dissolution rate, measuring their solubility and understanding their dissolution properties can effectively help solve the problem of nonwetting and nondiffusion.
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ENERGY
·
2020
·
IF 6.082
Yan Wang,Dong-Liang Zhong,Peter Englezos,Jin Yan,Bin-Bin Ge
The kinetics of semiclathrate hydrates formation with CO 2 in the presence of tetra- n -butyl ammonium bromide (TBAB), tetra- n -butyl phosphonium bromide (TBPB), and TBAB + TBPB were investigated. The experiments were conducted at the stoichiometric concentration of TBAB hydrate (2.57 mol%) and three subcoolings (Δ T = 6 K, 9 K, and 12 K) with the initial pressure fixed at 2.8 MPa. It was found that adding TBPB into the TBAB solution can promote hydrate nucleation, and this promotion effect at a lower subcooling (Δ T = 6 K) was stronger compared to that at higher subcoolings (Δ T = 9 K and 12 K). The gas consumption obtained in TBAB, TBPB, and TBAB + TBPB solutions decreased with the increase of subcooling, despite the increase of the rate of hydrate growth. At a given subcooling, gas consumption (CO 2 uptake) in TBAB + TBPB solutions was greater than that in TBAB and TBPB solutions, indicating that hydrate formation kinetics and the CO 2 storage capacity were improved in the TBAB + TBPB solution. The largest gas consumption was obtained at Δ T = 6 K in the TBAB + TBPB solution, which was 28.7% and 17.2% larger than those obtained in TBAB and TBPB solutions, respectively. Therefore, a mixture of TBAB + TBPB is a promising option to improve the kinetics of semiclathrate hydrate formation with CO 2 .
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CHEMICAL ENGINEERING JOURNAL
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2019
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IF 8.355
Ying Liu,Wei Miao,Xian Fang,Yulin Tang,Deli Wu,Shun Mao
The development of metal-free catalysts with high activity and stability for persulfate activation draws increasing attention due to their promising performance and environmental benignity. Herein, hierarchically porous nitrogen (N)-doped carbon (N C) with merits of highly-dispersed nitrogen, large surface area and controllable structure is synthesized. The as-prepared N C exhibits outstanding performance for peroxydisulfate activation in the degradation of diverse organic pollutants, as well as a wide working pH range of 3–10. Impressively, an annealing strategy can regulate C O and graphitic N contents in N C and their quantitative correlations with the reaction rate constants reveal that the C O and graphitic N in N C are active sites. Furthermore, peroxydisulfate activation by N C involves with three pathways in which the contribution from radicals (SO 4 − , OH) are comparatively weak and non-radical pathways including singlet oxygen ( 1 O 2 ) and electron transfer are dominant. The contribution of 1 O 2 is diminishing with delay of reaction while the electron transfer shows the opposite trend. Besides, good recycling performance is achieved by facile re-annealing of N C. This work provides new insights into the reaction mechanism of persulfate catalysis and can guide future catalyst development in advanced oxidation process.
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ENVIRONMENTAL POLLUTION
·
2018
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IF 4.358
Shuyan Zhao,Bohui Wang,Lingyan Zhu,Tiankun Liang,Meng Chen,Liping Yang,Jingping Lv,Lifen Liu
N-ethyl perfluorooctane sulfonamide (N-EtFOSA) is commonly known as the active ingredient of sulfluramid. It can be degraded to perfluorooctane sulfonic acid (PFOS) in biota and environment. Earthworms ( Eisenia fetida ) were exposed with N-EtFOSA to examine the bioaccumulation, elimination and metabolism of N-EtFOSA by the earthworms after in vivo and in vitro exposure. N-EtFOSA could be biodegraded in quartz sands to perfluorooctane sulfonamide (FOSA) and PFOS. In the in vivo tests, in addition to parent N-EtFOSA, three metabolites, including perfluorooctane sulfonamide acetate (FOSAA), FOSA and PFOS also accumulated in earthworms as a result of N-EtFOSA biotransformation , with FOSA as the predominant metabolite. The bioaccumulation factor (BAF) and uptake rate coefficient ( k u ) of N-EtFOSA from sand were 20.4 and 2.41·d −1 , respectively. The elimination rate constants ( k e ) decreased in the order FOSAA (0.130·d −1 ) > N-EtFOSA (0.118·d −1 ) > FOSA (0.073·d −1 ) > PFOS (0.051·d −1 ). The biotransformation of N-EtFOSA in earthworm was further confirmed by the in vitro test involving incubation of earthworm homogenates with N-EtFOSA. This work provides evidence on the accumulation and transformation of N-EtFOSA in terrestrial invertebrates and will be helpful to explore the indirect sources of FOSA and PFOS in environmental biota.
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Catalysts
·
2018
·Vol. 8
·期 5
·188
·
IF 3.465
Dalei Sun,Kaihong Xie,Yanxiong Fang,Xianghua Yang
One-pot synthesis ofN,N′-dialkylureas were successfully achieved from catalytic carbonylation of aliphatic primary amines with CO2as the carbon source and Y0.08Zr0.92O1.96mixed oxide (Yttria-stabilized zirconia, YSZ-8) as the heterogeneous catalyst. The yield of the target product was obtained up to 80.60% from a 48 h reaction with an aliphatic primary amine and 3.0 MPa CO2inN-methyl-2-pirrolidinone at 160 °C. A multi-pronged mechanistic study was carried out where factors that might influence the reaction efficiency were studied, including catalyst structure, substrates basicity, CO2pressure, solvent polarity and reaction time. The presence of oxygen vacancies in YSZ-8 was found to be essential for the carbonylation process by creating additional reduction potential for the activation of CO2which would lead to the key intermediate species.Keywords:Y0.08Zr0.92O1.96mixed oxide;N,N′-dialkylurea;carbonylation;CO2;heterogeneous catalysis
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JOURNAL OF CHEMICAL AND ENGINEERING DATA
·
2018
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IF 2.196
Yitong Dai,Wenqi Zhao,Haiyun Sun,Yongsheng Guo,Wenjun Fang
Densities (ρ) and viscosities (η) of ternary system n-dodecane + bicyclohexyl + n-butanol and three corresponding binary systems, n-dodecane + bicyclohexyl, n-dodecane + n-butanol, and bicyclohexyl + n-butanol, were measured at temperature range from 293.15 to 333.15 K in detail. Densities were obtained using a vibrating-tube densimeter. Viscosities were determined using an automatic microviscometer based on the rolling ball principle. The excess molar volumes (VmE) and the viscosity deviations (Δη) of each mixture were calculated with the measured data. The VmE and Δη values of three binary systems were fitted to the Redlich–Kister equation, and those of the ternary system were fitted to Nagata–Tamura, Singh, Clibuka, and Redlich–Kister semiempirical equations. The VmE values are negative for the binary system of n-dodecane + bicyclohexyl with the minimum at about x = 0.5, while those of binary systems n-dodecane + n-butanol and bicyclohexyl + n-butanol are positive over the entire concentration range. For the ternary system, the VmE values are subtotal positive and the Δη are negative over the entire concentration range. The nonideal behaviors of the mixtures are explained by physical interactions and structural effects between mixture components.
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JOURNAL OF CHEMICAL THERMODYNAMICS
·
2015
·
IF 2.679
Qi Zhang,Yang Yang,Limin Cheng,Cuicui Cao,Zhiwen Ding,Chunxiao Wang,Wenge Yang,Yonghong Hu,Yonglan Li
The solubility of dl -malic acid in binary solvent mixtures consisting of (methanol + acetonitrile); (methanol + N,N-dimethylformamide); and (methanol + isopropyl alcohol) was measured at temperatures ranging from (278.15 to 328.15) K by gravimetric method. Values of the solubility were fitted using modified Apelblat equation and Buchowski–Ksiazaczak λ h model. Computational results showed that the modified Apelblat equation was superior to the other equation. In addition, the thermodynamic properties of the solution process, including the Gibbs free energy, enthalpy, and entropy were calculated by the van’t Hoff analysis. This study provides valuable data for the dl -malic acid purification by the preferential crystallization procedure.
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SEPARATION AND PURIFICATION TECHNOLOGY
·
2024
·
IF 8.1
Meiling Liu,Liping Wang,Qilong Fan,Ningning Xiao,Zhiwen Chen,Yingying Dong,Chuanliang Zhao,Yongxia Sun,Xing Xu,Wendong Wang
Nitrogen (N)-doping has been reported effective to reinforce catalysis in advanced oxidation processes (AOPs) due to the formation of N-related active sites. Although several documents have reported that transition metal-nitrogen (metal-N x ) sites could work as reactive centers, the catalytic mechanism was hardly elucidated. In this study, N-doped cobalt oxide (N-CoO x ) was initiatively prepared via calcination in ammonia atmosphere to construct cobalt-nitrogen (Co-N x ) sites. The emergence of Co-N x sites effectively improved peroxymonosulfate (PMS) activation efficiency (above 5.8 times), leading to higher pollutant decomposition rate (95.8 % at 30 min) and kinetics constant (above 4.1 times). N introduction changed main facets of material and elevated adsorption energy (E ads ) (from −1.81 eV to −3.71 eV) between catalyst and PMS. Co atoms at Co-N x sites could donate larger quantity of electrons (from 1.088 e to 1.583 e) to PMS, therefore, contributed to stretching and breaking O–O bonds of PMS molecules to form reactive species. As a result, both radical and electron transfer pathway (ETP) were enhanced in the oxidation processes. Ultimately, the catalytic membrane coated with N-CoO x maintained 100 % treatment towards continuous antibiotic wastewater at environmentally relevant concentration (μg/L), realizing purification as well as separation of catalyst. This work systematically elaborates the superiority of Co-N x sites and unravels the underlying mechanism to inspire further study to metal-N x tailored catalysis.
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