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Science and Technology Service Network Initiative program of CAS[KFJ-STS-QYZD2021-02-002]
No full textInsights into the molecular mechanism of a new efficient whole-cell biocatalyst Enterobacter ludwigii YYP3 in 5-hydroxymethylfurfural reduction
No full textUpgrading of the bio-based platform chemical 5-hydroxymethylfurfural (HMF) into high-value derivatives is an important research topic, particularly in green and sustainable chemistry. Herein, we applied a new, highly HMF-tolerant strain, Enterobacter ludwigii YYP3, as a whole-cell biocatalyst for efficient reduction of HMF to 2,5-bis(hydroxymethyl)furan (BHMF). Upon process optimization, within only 3 h, BHMF was produced with a yield >99% and 98.5% selectivity using 100 mM HMF, resulting in the highest space time yield (4.2 g L-1 h(-1)) among the currently reported HMF bioreduction processes. In a fed-batch conversion, E. ludwigii YYP3 achieved large-scale production of 290 mM BHMF within 9 h and retained its high catalytic activity for three runs (27 h), suggesting an excellent cycling stability. Based on genome and transcriptome analysis, the molecular mechanism underlying the high HMF tolerance of E. ludwigii YYP3 was explored, primarily through the downregulation of genes related to amino acid biosynthetic and metabolic processes and upregulation of genes associated with DNA replication, recombination, and repair; biofilm formation; and redox homeostasis. Meanwhile, two novel short-chain dehydrogenase/reductase family oxidoreductases ElSDR-ykvO and ElSDR-SSP1627 were identified as target enzymes responsible for conversion of HMF to less toxic BHMF in E. ludwigii YYP3. Combined with structure and mutation analysis, the catalytic mechanisms of target enzymes were determined to be based on the active sites Ser, Tyr, and Lys. Our work not only confirms that E. ludwigii YYP3 has promising application prospects in large-scale production of BHMF, but also provides novel insights into understanding the molecular mechanism of HMF reduction
Ultra-stable high voltage lithium metal batteries enabled by solid garnet electrolyte surface-engineered with a grafted aromatics layer
No full textThe instability and Li2CO3 contaminants of garnet-type electrolytes exposed to air could lead to in its poor interfacial contact with the lithium metal. Generally, the thermal treatment temperature of garnet should overpass 700 & DEG;C to remove surface contaminants. Herein, we report a low temperature method in which con-taminants are converted to the aromatics lithiophilic interface via a simple azo reaction at 60 & DEG;C. The free radicals formed by the decomposition of the azo compound are grafted onto garnet, thereby the garnet compatibility in lithium metal batteries (LMBs) are improved effectively. The reaction mechanism is confirmed by density functional theory calculations, comprehensive electrochemical characterizations, and applying designed azo compounds. The modified garnet membrane shows a high mechanical property and reduced interfacial impedance, high Young's modulus of 169.99 GPa and ionic conductivity of 0.457 mS/cm at 20?. Subsequently, combined XPS depth etching and TOF-SIMS characterizations show that the interfacial layer is composed of a rich C-F bond surface layer and a rich-LiF bottom layer, enabling rapid transport and uniform deposition of lithium ions. Moreover, the superior cycling stability facilitated by modified composite electrolyte is demonstrated in Li/LiFePO4 and Li/LiNi0.5Co0.2Mn0.3O2 full batteries. This new conversion chemistry via azo compound provides a practical solution for achieving high-energy solid-state LMBs
Photothermal catalytic oxidation of toluene with enhanced efficiency over constructed CuMn2O4/Mn2O3 heterojunction catalyst
No full textPhotothermal catalyst oxidation of VOCs is a hot issue in the air purifier field due to the reducing of secondary energy consumption. Herein, we reported a photothermal catalyst CuMn2O4/Mn2O3 with heterojunction for catalytic oxidizing toluene with high efficiency through sol-gel method followed different calcination temperature. Under the irradiation of 700 mW/cm(2) Xe lamp simulated sun light, the CuMn2O4/Mn2O3 catalyst exhibited excellent full spectrum light absorption capacity, photo-thermal conversion ability and toluene conversion performance with a 90% toluene conversion (T = 233 degrees C, WHSV = 30,000 mL/gmiddoth), together with a good catalytic stability. The excellent performance can be attributed to the synergistic effect of abundant oxygen vacancies, Mn3+ active sites and heterojunctions between CuMn2O4 and Mn2O3 due to the XPS, H-2-TPR, UPS characterizations
Revealing the rate-limiting electrode of lithium batteries at high rates and mass loadings
No full textLithium-ion batteries with superior capacities and rate performance are needed due to the soaring demands for higher energy and power device requirements. However, the main hurdle on achieving this predominately results from the poor rate performance of electrode, which is related to thermodynamic limitations and slow kinetics. To determine the rate-limiting electrode in NMC622 vs graphite cells, a methodology based upon the galvanic intermittent titration technique, for investigating the diffusion and reaction kinetics from the observed over -potential at each electrode has been developed. Variable current densities have been used to simultaneously extract the thermodynamic and kinetic properties of each electrode with increasing mass loading. Graphite is observed to reach its thermodynamic limits quicker than NMC, due to the flat plateaus and overpotentials observed from the charge transfer kinetics and mass transport. At high rates and high mass loadings, the graphite electrode is responsible for limiting both Li+ diffusion and reaction rates in full cells. Slow diffusion kinetics are caused by the transport of the electrolyte in the porous electrode, which limits the availability of Li+ for reaction at the surface of graphite. This methodology is proposed as a fast single technique for comprehensively parameterizing the rate limitations observed in a full cell configuration
Regulation on both pore structure and pressure-resistant property of uniform agarose microspheres for high-resolution chromatography
No full textHow to improve the performance of chromatographic media is very important in chromatography. Uni-form agarose microspheres were successfully prepared using membrane emulsification method with a controllable particle size, followed by multi-step crosslinking and dextran-grafting, respectively. To obtain both fine pore structure and good pressure-resistant property, the effects of both dextran-grafting and crosslinking process were studied carefully and also, the preparation conditions were delicately adjusted. Inverse size-exclusion chromatography was used for determining the pore structure of these agarose microspheres. Uniform agarose microspheres with an average particle size of about 8 mu m were obtained with regularly spherical, transparent and smooth appearance. By introducing a certain molecular weight of dextran or pentaerythritol glycidyl ether at different crosslinking steps, both the pressure-resistant and the chromatographic properties of microspheres were improved. Both the maximum flow velocity and the corresponding pressure drop increased with the decrease of the molecular weight of dextran, i.e., 99 cm/h and 3.22 MPa, respectively, using dextran T3 (3 kDa). The average pore size of agarose microspheres decreased from 6.04 +/- 0.56 nm to 2.50 +/- 0.12 nm with the increase of the molecular weight of dextran from dextran T3 (3 kDa) to dextran T100 (100 kDa), with a high resolution obtained for a certain molecular range of model proteins. Also, the pressure-resistant property was highly improved in multi-step crosslinking process, with a maximum flow velocity of 107 cm/h and a corresponding pressure drop of 3.62 MPa obtained after the whole crosslinking steps. The average pore size of agarose microspheres was 3.72 & PLUSMN;0.32, 3.90 +/- 0.21 and 3.60 +/- 0.27 nm for the introduction of pentaerythritol glycidyl ether as the crosslinking agent at different steps, respectively. These uniform dextran-grafted agarose microspheres have a finely controllable molecular range with a high resolution compared with traditional ones, which are beneficial for chromatographic selectivity. Therefore, they are very useful for high-resolution chromatography and have wide applications in downstream process.(c) 2022 Elsevier B.V. All rights reserved
Steam Explosion Pretreatment for Improving Wheat Bran Extrusion Capacity
No full textExtrusion improves the texture of wheat bran and enhances its product edibility, making it a promising processing method. However, the extrusion performance of wheat bran without any treatment is not satisfactory and limits the utilization of wheat bran in food processing. In this study, steam explosion pretreatment was used to treat wheat bran to investigate its promotion of wheat bran extrusion. The results showed that steam explosion could increase the extrusion ratio of wheat bran extrudate by 36%. Grinding the steam-exploded wheat bran extrudate yields wheat bran flour with smaller particle sizes and higher cell wall breakage. Fourier transform infrared spectroscopy and chemical composition results revealed that steam explosion degraded insoluble dietary fiber and disrupted the dense structure of the cell wall in wheat bran. The water-extracted arabinoxylan and soluble dietary fiber content of steam-exploded wheat bran were 13.95% and 7.47%, respectively, improved by 1567.42% and 241.75% compared to untreated samples. The total phenol and flavonoid contents, water solubility index, and cation exchange capacity of steam-exploded wheat bran extrudate were all superior to raw wheat bran extrudate. In summary, this study demonstrates that steam explosion improves the extrusion capacity of wheat bran and facilitates its utilization
Collision dependent silver nucleation regulated by chemical diffusion and reaction
No full textNucleation is widely present in nature, from food production to haze generation. Owe to the spatiotem-poral limitation in catching the dynamic characters of nucleation process, the theoretical development and the control technique of nucleation is far behind the demand. Here we report a strategy of controlling nucleation process via manipulating the collision of nucleation units, with the aim of disclosing the mechanism dominating the nucleation process. Silver nucleation is simulated at different collision con-ditions which is regulated by chemicals diffusion and reaction rate. It is found that the nucleation rate has a good linear relationship with the collision frequency, suggesting a collision dependent nucleation model. This model is evaluated by particles-based silver aggregation and validated by experiments con-ducted in an in-situ electron microscopy. Furthermore, the model is applied to the improved synthesis of silver catalysts for selective partial oxidation of ethylene.(c) 2022 Elsevier Ltd. All rights reserved