Table of Content

20 December 2002, Volume 2 Issue 6

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6

Glutamine Production by the Enzyme Method

YANG Chun-yu; MA Cui-qing; XU Ping; ZHANG Zhao-bin; LI Jin-shan

. 2002, 2(6):  0-0. 

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After enzymatic lysis and ultrasonication, Corynebacterium glutamicum, which produces high yield of glutamine, can release glutamine synthetase (GS) with high activity. The GS extracellular catalysis is regulated by a few conditions and factors. By mono-factor experiment, response experiment and orthogonal experiment, the suitable conditions for GS extracellular catalysis are determined: in the reaction mixture, the most significant factor is ATP, and the concentration of ATP is 40~50 mmol/L. The amount of enzyme also shows strong effect to the reaction. Using the cell-free extracts, the effects of some factors on the GS conversion in the extracellular reaction are examined and the optimal condition for GS extracellular catalysis obtained. The highest conversion is 7.1 g/L and the conversion yield is 94.8%.

Lipase Production by Immobilized Rhizopus arrhizus Cells and Enzymatic Synthesis of Monoglyceride

YIN Chun-hua; FU Si-zhou; XU Jia-li; TAN Tian-wei

. 2002, 2(6):  0-0. 

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Lipase production by fermentation with immobilized Rhizopus arrhizus was studied, in which the lipase activity by perlite adsorbtion Rhizopus cells reached 125 U/ml, 8 times as that by fermentation without carriers. The immobilized Rhizopus arrhizus cells on carriers after fermentation also showed high lipase activity. Synthesis of monoglyceride by lipase and the immobilized cells on carriers after fermentation was tested, and proved to be an effective method for production of monoglyceride.

Preparation of Poly-porous Poly(NVP-co-NMBA) Sorbent and Octanol Solution of Adsorption of Dibenzothiophene in Dilute

SHAN Guo-bin; LIU Hui-zhou

. 2002, 2(6):  0-0. 

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A porous polymeric sorbent was prepared with sucrose as pore-forming additive, and the sorbent beads are superior to non-porous polymeric sorbent in adsorption of DBT from a model gasoline. Adsorption of 16 mg/g DBT was achieved under the condition of 50 g/L of the polymeric beads at initial DBT concentration of 1.26 g/L. The sorbent beads are easily desorbed with toluene and can be reused with stabilized adsorption capacity.

Effect of Activating Conditions on the Characteristics of Activated Coke

ZHANG Shou-yu; ZHU Ting-yu; WANG Yang;LU Jun-fu;YUE Guang-xi; YIN Xian-fen

. 2002, 2(6):  0-0. 

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The effects of coal type and activation conditions on the desulfurization capability of activated coke in a fluidized bed were studied. The results show that compared with Datong coal, Binxian coal is a better raw material for activated coke used in flue gas desulfurization. The iodine value, benzoic acid sorption and sulfur capacity of the activated coke prepared from Binxian coal increase with activation temperature, activation time and concentration of water vapor in the activation agent. The activated coke with the sulfur capacity of 174~275 mg/g can be prepared from Binxian coal under the following activation conditions: activation temperature of 800~900oC, activation time of 20~60 min, and concentration of water vapor of 30%~80%(j).

Influence of Riser Shape and Configuration on Flow Characteristics in the Riser

CHEN Zhi-wei; LUO Bao-lin; FENG Wei; REN Tian-rui

. 2002, 2(6):  0-0. 

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The rapid expansion of oil gas has large influence on the operating performance and flow characteristics in the riser of FCCU. In the present work, the effect of riser shape on flow characteristics and the suitability of conical riser (diffuser) for expanding oil-gas flow were investigated. Auxiliary gas was introduced into the riser to imitate the expansion of oil gas in the riser in experiments. The axial profile of pressure and the radial profiles of particle velocity and voidage were measured. Comparison of experimental results in the tube-riser and the conical-riser shows that the particle concentration in the conical riser is almost uniform, pressure drop is lower than that in the tube riser, and flow characteristics are greatly improved. It seems that the conical riser (diffuser) has the advantage of operating flexibility over the tube riser, and is suitable for the rapid expanding oil gas.

Surface Characteristics of Heavy Calcium Carbonate Modified by Polymer Grafting

WU Wei; LU Shou-ci; CHEN Jian-feng; SHAO Lei

. 2002, 2(6):  0-0. 

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A new process of polymer grafting modification of CaCO3 is proposed, which combines the action of mechanical force, thermal and chemical effects. The modification time is reduced greatly and the modification effect is improved. Infrared spectrum (IR), gel permeation chromatography (GPC), X photoelectron spectrum (XPS) and thermogravimetry (TG) analyses are employed to characterize the modified surface of heavy calcium carbonate by styrene grafting. It is proven that chemically absorbed multi-layer polystyrene exists on the surface of the modified particles apart from grafted polystyrene. The primary surface characteristics of heavy calcium carbonate are deduced based on physico-chemical analyses. Radical polymerization is regarded as the primary modification mechanism.

Fermentation of Cellulosic Pyrolysate for Producing Ethanol

YU Zhi-sheng; ZHANG Hong-xun

. 2002, 2(6):  0-0. 

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The cellulosic pyrolysate mainly containing 1,6-anhydro-b-D-glucopyranose (levoglucosan) could be hydrolyzed to glucose and further fermented to ethanol with microorganisms. Among the various hydrolysis treatments, the highest glucose yield (17.35%) was obtained by 0.2 mol/L H2SO4 at 121oC for 20 min. Such hydrolysate treated by neutralization with Ca(OH)2 and absorption with diatomite for detoxification was used for fermentation to ethanol by Candida krusei YZ-1. The yield was 0.42 g/g (ethanol/glucose), up to 84% of the theoretical yield. Zymomonas mobilis performed very poorly in fermenting all treated pyrolyate to ethanol.

Cleaner Production of Wheat Straw Pulp

HUANG Guo-lin;CHEN Zhong-sheng;ZHANG Cheng-fang

. 2002, 2(6):  0-0. 

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A pulping method using NH4OH with less amount of KOH as cooking liquor on wheat straw was developed. KOH could reduce consumption of NH3 and cooking time for its strong alkalinity. The effects of various pulping conditions such as composition of cooking liquor, liquid-to-solid ratio, maximum temperature, cooking time to the maximum temperature and cooking time at the maximum temperature were studied. Experimental results indicated that the rate of delignification was 85.12% and the pulp yield was 49.65% under suitable pulping conditions. It looks promising to use black liquor containing nitrogen, phosphorus, potassium and organic substance as fertilizer resources for agricultural production. A new pattern of ecological cycling may be set up between paper industry and farming.

Preliminary Research on Cryopreservation of Saussurea medusa Maxim Callus

CHEN Shu-an; WANG Xiao-dong; ZHAO Bing; WANG Yu-chun

. 2002, 2(6):  0-0. 

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The cryopreservation condition of Saussurea medusa callus was studied. The results indicated that preculture, cryoprotectant, pretreatment, recovery and washing conditions affected the survival rate of Saussurea medusa callus. The preculture medium was MS solid culture medium supplemented with 5% dimethyl sulfoxide. The optimum composition of cryoprotectant was 15% ethyleneglycol, 15% simethyl sulfoxide, 30% glycerol and 0.4 mol/L sucrose. The pretreatment temperature and time were 15oC and 10 min, respectively. The recovery temperature was 25~40oC. The survival rate of Saussurea medusa callus was 58.5% after washed by MS liquid medium with 1.2 mol/L sucrose for 3 times (10 min for each time ) at 25oC.

Measurement and Correlation of Gas Holdup in a Pressurized Bubble Column

ZHANG Tong-wang; JIN Hai-bo; HE Guang-xiang; TONG Ze-min; ZHU Jian-hua

. 2002, 2(6):  0-0. 

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Gas holdup is measured in a pressurized bubble column 0.3 m in diameter and 6.6 m in height. The effects of surface tension, viscosity and pressure on gas holdup are investigated. Gas holdup decreases with the increase of surface tension and viscosity, but increases with the increases of pressure. An empirical correlation is also presented.

Effects of Pb, Cd, and Zn on Oxidative Stress and Antioxidative Ability in Phragmites australis

WANG Zheng-qiu; JIANG Xing-yu; WANG Chang-hai

. 2002, 2(6):  0-0. 

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Superoxide anion radical, MDA, electrolyte leakage, as well as activities of SOD and POD in the leaf and root cells of Phragmite australis were investigated under the conditions of Pb, Cd, and Zn stresses. Under these conditions, the accumulation of superoxide anion radical and MDA, and the electrolyte leakage of the cell membrane increased in the plant cells, which indicated that the peroxidation of cell membrane lipid was induced and the membrane system was damaged. Higher activity of SOD and POD, two key enzymes of the antioxidative system, was observed in all Pb, Cd, and Zn treated plant cells. These results suggest that the enhancement of peroxidation of membrane lipid induced by superoxide anion radical may be one of the heavy metal injury mechanisms in P. asutralis. Furthermore, the accumulation of the two enzymes would be part of general defense strategies to cope with oxidative stress.

Preparation and Characterization of LiNi0.8M0.2O2 with Various Doping Elements for Lithium Battery Cathod

LI Hui; YANG Shang-lin; ZHAI Yu-chun; TIAN Yan-wen

. 2002, 2(6):  0-0. 

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With doping different elements (M), a series of compounds LiNi0.8M0.2O2 used as cathode materials in lithium ion batteries were prepared by solid reaction under increased oxygen pressure. It was found that the doped Al, Mn and Ti can improve the properties in overcharge tolerance and cyclic capacity. The discharge capacity was almost kept constant after three cycles at high charging voltage ranging from 4.2 to 4.8 V. XRD and SEM analyses revealed that doping Al, Mn and Ti increased the orderness of the LiNiO2 material in the hexagonal phase and maintained the layered structure during the charging/discharging process. However, doping other elements decreased the orderness of the material structure, which clearly affected the electrochemical properties of the materials.

Recovery of RE from Weishan Rare Earth Concentrate with Chlorination Roasting after Fluorine-fixing Treatment

SHI Wen-zhong; ZHU Guo-cai;ZHANG Zhi-geng; WANG Jing-yan; CHI Ru-an

. 2002, 2(6):  0-0. 

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A process for recovery of RE from the Weishan rare earth concentrate was developed by incorporation of fluorine-fixing and RE concentrate chlorinating with ammonium chloride. The suitable conditions were determined as follows: Fluorine-fixing time of 50 min, MgO dosage mMgO/more=1:20 at 550oC. Chlorinating the fluorine-fixed calcine by 60 min, with NH4Cl dosage mNH4Cl/more=1.2:1 at 480oC, the leaching recovery of RE reaches 87.8% under the above conditions. The possible reactions in the fluorine-fixing process were discussed with the X-ray diffraction spectrum.

Mechanism of Extraction of Oxalic Acid by Quaternary Ammonium Salt

TANG Hong-ping; YANG Ming-de; HE Pei-jiong

. 2002, 2(6):  0-0. 

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Quaternary ammonium salt (N263) has strong affinity with Au(CN)2– in cyanide solutions, but Au is not readily stripped. Stripping by acidic thiourea solutions with air sparging shows good promise, and the stripping efficiency is improved significantly by addition of oxalic acid in the stripping solution. It is found that oxalic acid is extracted into the organic phase during stripping. In this paper, the mechanism of extraction of oxalic acid is studied by 3 models of extraction equilibrium and infrared spectrum. It is shown that oxalic acid is extracted mainly as neutral molecule (ratio to N263 is 1:1), which is associated with the anions of quaternary ammonium salts by hydrogen bond. There are still small quantities of oxalic acid anions H3C4O8– which exchange with Cl– of N263 to form 1:2 ionic pairs with the cations of N263.

Research and Application of Synthesis of Nanopowders by Microwave Plasma-enhanced Chemical Vapor Deposition Method

HUANG Sheng-qiao; MA Bing

. 2002, 2(6):  0-0. 

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The principle and some characteristics of MPECVD technology were reviewed. The superiorities of nanopowders synthesis by MPECVD over other methods were analyzed. Some recent development of synthesis of nanopowders by MPECVD in China and other countries were reviewed.

Chemical Plating of Cobalt on Ni(OH)2 Spheres and the Discharge Performance of Electrodes Made Thereof

LI Fan; ZHANG Deng-jun; LI Bao-hou; LUO Shi-min; ZHAO Xiao-feng

. 2002, 2(6):  0-0. 

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Cobalt was deposited on spherical nickel hydroxide by electroless plating, using hydrazine or sodium hypophosphite as reductive agent and ammonia or potassium sodium tartrate as complexing agent, respectively. Under the condition of the same amount of Co deposited, phases of product were detected by XRD, the morphology was observed by SEM, and its electrode discharge (1 C rate) capacity was determined. It is found that Co-coating can increase the discharge capacity by 11% to 32%.

Progress in Improving the Asymmetric Enantioselectivity of Lipase for Catalyzing Asymmetric Reaction

NIE Yao; XU Yan;WANG Dong

. 2002, 2(6):  0-0. 

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Lipase has been extensively used in asymmetric reaction for producing optically pure compounds. Focused on improving the enantioselectivity of lipase for catalyzing asymmetric reaction, the recent researches have been summarized in this article, including reformation of lipase structure, reaction condition optimization, improvement of asymmetric reaction process and enantioselective inhibitation. Microwave irradiation can also be used to enhance the enantioselectivity of lipase in some level. Some traditional and new approaches, such as immobilization of enzyme, chemical modification, in vitro directed evolution, bio-imprinting, and optimization of reaction conditions were introduced.

Application of Artificial Neural Network to Polystyrene Spheres Preparation

ZHANG Hui; ZHAO Xiao-feng; TANG Qing; LI Wen-chao

. 2002, 2(6):  0-0. 

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Artificial neural network method was applied to polystyrene spheres preparation. Relation was established between the preparation factors of polystyrene spheres and the relative standard deviation of prepared sphere diameters. Calculation results were in agreement with experimental ones.

Preparation Experiment on Nanosized ZnNi Ferrite Powders

ZHU Wei-chang; YAN Yong; DING Fei

. 2002, 2(6):  0-0. 

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ZnxNi1-xFe2O4 nanosized powders were prepared by calcined basic carbonate precursor synthesized from solid FeSO4×7H2O, NiSO4×6H2O, ZnSO4×7H2O, NaHCO3 salts and concentrated NaOH solution, then the precursor was calcined at 350oC for 1 h. The microstructure of the obtained sample was examined by XRD and TEM analyses. The results show that the size of nanocrystalites is about 30 nm. Changing proportion of ZnSO4×7H2O and NiSO4×6H2O, nanocrystalline Zn0.9Ni0.1Fe2O4, Zn0.8Ni0.2Fe2O4, Zn0.7Ni0.3Fe2O4, Zn0.6Ni0.4Fe2O4 and Zn0.5Ni0.5Fe2O4 were also prepared.