Combining metabolic engineering and biocompatible chemistry for high-yield production of homo-diacetyl and homo-(S,S)-2,3-butanediol

Liu, J.,Chan, S.H.J.,Brock-Nannestad, T.,Chen, J.,Lee, S.Y.,Solem, C.,Jensen, P.R. Academic Press 2016 Metabolic engineering Vol.36 No.-

Biocompatible chemistry is gaining increasing attention because of its potential within biotechnology for expanding the repertoire of biological transformations carried out by enzymes. Here we demonstrate how biocompatible chemistry can be used for synthesizing valuable compounds as well as for linking metabolic pathways to achieve redox balance and rescued growth. By comprehensive rerouting of metabolism, activation of respiration, and finally metal ion catalysis, we successfully managed to convert the homolactic bacterium Lactococcus lactis into a homo-diacetyl producer with high titer (95mM or 8.2g/L) and high yield (87% of the theoretical maximum). Subsequently, the pathway was extended to (S,S)-2,3-butanediol (S-BDO) through efficiently linking two metabolic pathways via chemical catalysis. This resulted in efficient homo-S-BDO production with a titer of 74mM (6.7g/L) S-BDO and a yield of 82%. The diacetyl and S-BDO production rates and yields obtained are the highest ever reported, demonstrating the promising combination of metabolic engineering and biocompatible chemistry as well as the great potential of L. lactis as a new production platform.

Magnetically separable sulfur-doped SnFe₂O₄/graphene nanohybrids for effective photocatalytic purification of wastewater under visible light

Jia, Y.,Wu, C.,Lee, B.W.,Liu, C.,Kang, S.,Lee, T.,Park, Y.C.,Yoo, R.,Lee, W. Elsevier Scientific Pub. Co 2017 Journal of hazardous materials Vol.338 No.-

In this report, magnetically recoverable sulfur-doped SnFe<SUB>2</SUB>O<SUB>4</SUB>/graphene (S-SFO/GR) nanohybrids have been successfully developed via a facile solvothermal method. The characterizations on the structural, morphology, and optical properties of the nanohybrids indicate that S-SFO particles are successfully embedded on the GR nanosheets. The photocatalytic activity has been evaluated by photocatalytic degradation of chlorotetracycline under visible light irradiation. Among the composites with various mass ratios, the quasi-first-order rate constant of the nanohybrids formed with 9wt% S in SFO and 15wt% GR (9S-SFO/GR-15) can reach as high as 1.83min<SUP>-1</SUP>, which is much higher than that of SFO (0.68min<SUP>-1</SUP>) and SFO/GR (0.91min<SUP>-1</SUP>), confirming the important role of S and GR for the photocatalytic process. The combination of the three components of S, SFO, and GR has enhanced the visible light absorption capability and inhibited the recombination of photogenerated electron-hole. The 9S-SFO/GR-15 nanohybrids can be recovered easily by a magnet and reused for five times with remained photocatalytic efficiency about 70%. A possible catalytic mechanism explaining the efficient photocatalytic performances of the prepared nanohybrids has been proposed.

Nanostructured nitrogen-doped mesoporous carbon derived from polyacrylonitrile for advanced lithium sulfur batteries

Liu, Y.,Zhao, X.,Chauhan, G.S.,Ahn, J.H. New York] ; North-Holland 2016 APPLIED SURFACE SCIENCE - Vol.380 No.-

Nitrogen doping in carbon matrix can effectively improve the wettability of electrolyte and increase electric conductivity of carbon by ensuring fast transfer of ions. We synthesized a series of nitrogen-doped mesoporous carbons (CPANs) via in situ polymerization of polyacrylonitrile (PAN) in SBA-15 template followed by carbonization at different temperatures. Carbonization results in the formation of ladder structure which enhances the stability of the matrix. In this study, CPAN-800, carbon matrix synthesized by the carbonization at 800<SUP>o</SUP>C, was found to possess many desirable properties such as high specific surface area and pore volume, moderate nitrogen content, and highly ordered mesoporous structure. Therefore, it was used to prepare S/CPAN-800 composite as cathode material in lithium sulfur (Li-S) batteries. The S/CPAN-800 composite was proved to be an excellent material for Li-S cells which delivered a high initial discharge capacity of 1585mAhg<SUP>-1</SUP> and enhanced capacity retention of 862mAhg<SUP>-1</SUP> at 0.1C after 100 cycles.

Hot Deformation Behavior and Dynamic Recrystallization Characteristics of 12Cr Ultra‑Super‑Critical Rotor Steel

Y. Xu,J. S. Liu,Y. X. Jiao 대한금속·재료학회 2019 METALS AND MATERIALS International Vol.25 No.4

In this paper, the constitutive model and dynamic recrystallization characteristics of 12Cr ultra-super-critical rotor steelwere investigated quantitatively during hot deformation. A series of axisymmetric hot compression tests at temperaturesfrom 900 to 1200 °C under strain rates of 0.001–1 s−1 were conducted on a Gleeble−1500D thermal simulator. Based on theexperimental true stress–strain curves varying with temperature and strain rates, a complete constitutive model was establishedand all material parameters in the model could be expressed as a function of strain using a fifth order polynomial fit. The proposed model was verified so as to have the capability of accurately predicting the flow behaviour with an averageabsolute relative error of < 2.82%. Meanwhile, after hot deformation the microstructure was observed via electron backscatterdiffraction technology. Then, the dependence of the characteristic parameters on the Zener–Hollomon parameter wereconfirmed. Furthermore, the kinetics equation of dynamic recrystallization was obtained, which included the flow stresscalculated based on the evolution equation of the dislocation density during the work hardening-dynamic recovery stage. The result indicated that the predicted values for dynamic recrystallization volume fraction and flow stress were in line withthe experimental values.

Effects of Dietary Energy Density on Growth, Carcass Quality and mRNA Expression of Fatty Acid Synthase and Hormone-sensitive Lipase in Finishing Pigs

Liu, Z.H.,Yang, F.Y.,Kong, L.J.,Lai, C.H.,Piao, X.S.,Gu, Y.H.,Ou, X.Q. Asian Australasian Association of Animal Productio 2007 Animal Bioscience Vol.20 No.10

A single factorial experiment was conducted to test the effects of three dietary levels of energy on mRNA expression of fatty acid synthase (FAS-mRNA) and hormone-sensitive lipase (HSL-mRNA) and their association with intramuscular fat in finishing pigs. 72 crossbred (Large $White{\times}Rongchang$) barrows with an average initial body weight of 20.71 (s.e. 0.1) kg, were randomly allotted to three dietary treatments (11.75, 13.05 and 14.36 MJ DE/kg) and fed until slaughtered at 100 or 101 kg. The diets were iso-nitrogenous and iso-essential amino acids. The growth performances including the duration of finishing were changed linearly (p<0.05) or quadratically (p<0.05) with increased dietary energy levels. The effects of dietary energy content on the percentage of external fat, intramuscular backfat and the fat thickness were linear (p<0.05). The content of dietary energy increased FAS-mRNA linearly or quadratically, while HSL-mRNA decreased linearly or quadratically in backfat and Longissmus dorsi muscle. Meanwhile, significant positive correlations (p<0.05) were found between energy level and intramuscular fat, FAS-mRNA or the ratio of FAS-mRNA to HSL-mRNA, between the ratio of FAS-mRNA to HSL-mRNA and intramuscular fat. However, the correlations between HSL mRNA and dietary energy or intramuscular fat were negative (p<0.05). The results indicated that dietary energy level regulates lipid accumulation, especially intramuscular fat, possibly by modulating the mRNA of FAS and HSL together rather than individually.

Synthesis of well-aligned carbon nanotubes with open tips

Liu, B.C.,Lee, T.J.,Jung, S.I.,Park, C.Y.,Choa, Y.H.,Lee, C.J. Elsevier 2005 Carbon Vol.43 No.7

<P><B>Abstract</B></P><P>Large amounts of well-aligned carbon nanotubes (CNTs) with open tips have been produced by pyrolysis of iron(II) phthalocyanine. The aligned CNTs have an average length about 10μm and diameters ranging from 92 to 229nm. Some of produced CNTs showed Y-junction structure due to the self-joint growth of two neighboring CNTs. The well-aligned CNTs indicated a bamboo-shaped multiwalled structure and fairly good crystallinity. The aligned CNTs follow tip growth mechanism.</P>

병렬형 하이브리드 자동차의 SimulationX 모델 개발 및 연비 시뮬레이션

서영우(Y. W. Seo),한성민(S. M. Han),여현승(H. S. Yeo),이석우(S. W. Lee),류하오(Hao Liu) 유공압건설기계학회 2022 유공압건설기계학회 학술대회논문집 Vol.2022 No.12

Hybrid Electric Vehicles (HEVs) are an important seed in the process of converting from traditional internal combustion engine vehicles to eco-friendly vehicles. HEVs that use two energy sources have a complex structure, and thus, these two energy sources work independently/alternatively/jointly depending on road driving conditions in order to improve fuel efficiency. As HEVs are developed, it is becoming important to understand the operating principles and to interpret fuel economy performance in simulations. This research used simulationX, a commercial multi-domain analysis S/W, to develop a model for a parallel type hybrid vehicles, and implement fuel efficiency analysis. First, the heat engine, battery, electric motor, power train, etc. were modeled in a simulationX environment based on the parallel hybrid vehicle structure. Then, fuel efficiency analysis simulation was performed on driving condition of NEDC (New European Driving Cycle). The developed simulationX model for parallel type hybrid vehicle is prepared to develop a controller for fuel efficiency improvement in the future work.

Increase of critical current density with doping carbon nano-tubes in YBa₂Cu₃O₇₋<i>_δ</i>

Dadras, S.,Liu, Y.,Chai, Y.S.,Daadmehr, V.,Kim, K.H. Elsevier 2009 Physica. C, Superconductivity Vol.469 No.1

<P><B>Abstract</B></P><P>The effects of carbon nano-tubes (CNTs) on the crystal structure and superconducting properties of YBa<SUB>2</SUB>Cu<SUB>3</SUB>O<SUB>7−</SUB><I><SUB>δ</SUB></I> (Y-123) compound were studied. Samples were synthesized using standard solid-state reaction technique by adding CNT up to 1wt% and X-ray diffraction data confirm the single phase orthorhombic structure for all the samples. Current–voltage measurements in magnetic fields up to 9T were used to study the pinning energy <I>U<SUB>J</SUB></I> and critical current density <I>J</I><SUB>c</SUB> as a function of magnetic field at fixed temperature. We find that while <I>T</I><SUB>c</SUB> does not change much with the CNT doping (91–92K), both <I>U<SUB>J</SUB></I> and <I>J</I><SUB>c</SUB> increase systematically up to 0.7wt% CNT doping in a broad magnetic field ranges between 0.1 and 9T and <I>J</I><SUB>c</SUB> in the 0.7wt% CNT doped sample is at least 10 times larger than that of the pure Y-123. The scanning electron microscope image shows that CNTs are forming an electrical-network between grains. These observations suggest that the CNT addition to the Y-123-compounds improve the electrical connection between superconducting grains to result in the <I>J</I><SUB>c</SUB> increase.</P>

The Expression of Porcine Adiponectin and Stearoyl Coenzyme a Desaturase Genes in Differentiating Adipocytes

Wang, P.H.,Ko, Y.H.,Liu, B.H.,Peng, H.M.,Lee, M.Y.,Chen, C.Y.,Li, Y.C.,Ding, S.T. Asian Australasian Association of Animal Productio 2004 Animal Bioscience Vol.17 No.5

The gene expression of porcine adiponectin and stearoyl coenzyme A desaturase (SCD) was investigated in this study. The partial gene sequences for adiponectin and SCD were amplified by RT-PCR from subcutaneous adipose tissue and cloned by TA cloning techniques. Sequences of these genes were determined and found to be highly homologous to that of other species, suggesting similar function of these genes as in other species. The transcripts of these adipocyte-related genes in pig tissues were measured by Northern analysis. The transcripts for adiponectin and SCD were highly expressed in porcine subcutaneous adipose tissue; the transcripts for SCD were also barely detected in the liver, but the greatest concentrations were in the adipose tissue. In porcine stromalvascular cells (S/V cells) cultured in vitro, transcripts for adiponectin and SCD increased gradually during adipocyte differentiation. The level of adipocyte adiponectin mRNA was associated with late adipocyte differentiation, indicating the gene may not be involved in adipocyte differentiation but has great importance in porcine adipocyte functions. The SCD transcripts were not detectable until 2 d after induction of adipocyte differentiation. It was highly expressed in differentiating porcine adipocytes (2 to 10 d after the induction of adipocyte differentiation), indicating a significant role of SCD in adipocytes.

SimulationX 기반 자동차 semi-active 현가장치의 모델 개발 및 특성 해석

정인태(I. T. Jeong),정동석(D. S. Jeong),정원식(W. S. Jeong),이성민(S. M. Lee),유보연(B. Y. Yoo),장대범(D. B. Jang),서영우(Y. W. Seo),한성민(S. M. Han),이석우(S. W. Lee),여현승(H. S. Yeo),류하오(Hao Liu) 유공압건설기계학회 2022 유공압건설기계학회 학술대회논문집 Vol.2022 No.12

The semi-active suspension system controls the damping force of the vehicle damper to simultaneously improve the steering stability (handling) and ride comfort of the vehicle. In order to improve the ride comfort of a passenger car, performance analysis is required through modeling and simulation adaptation of a semi-active suspension system. This study used SimulationX, a commercial multi-domain analysis S/W, and modeling about 1/4 car of the semi-active suspension system. The damping force was controlled through a given performance of the damper. The developed SimulationX-based semi-active suspension system model is prepared for future controller development research.