Table of Content

20 October 2003, Volume 3 Issue 5

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5

Biosynthesis of Polyhydroxyalkanoates by Ralstonia eutropha with Short-chain-length Organic Acids

YAN Qun; DU Guo-cheng; CHEN Jian

. 2003, 3(5):  0-0. 

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Separation of dimethyl carbonate (DMC) and methanol (MeOH) is very difficult due to the azeotrope of DMC and MeOH, the pressure swing method is an effective method for separation of DMC and MeOH azeotrope. In this paper, a joint process of high-pressure distillation and atmospheric distillation was investigated. Binary interaction parameters of the UNQUAC model between MeOH and DMC were regressed against experimental data of vapor liquid equilibria of MeOH and DMC, the applicable range of the model is: pressure 0.1~1.5 MPa, temperature 337~440 K. Based on the thermodynamic model, the separation flowsheet, inclnding a high-pressure distillation column and an atmospheric distillation column in series, was simulated and analyzed. Sensitivity of operation factors was discussed and the optimum operation parameters were proposed. The optimal parameters of the high-pressure distillation column were as follows: stage number 40, feed stage 29, reflux ratio 7~10, operation pressure 1.0~1.5 MPa.

Leaching of a Low-grade Refractory Tantalum–Niobium Ore by KOH Sub-molten Salt

ZHOU Hong-ming; ZHENG Shi-li; ZHANG Yi

. 2003, 3(5):  0-0. 

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Production of lignin peroxidase (LiP) and manganese peroxidase (MnP) in three kinds of reactors (stirred tank reactor, bubble column reactor and aeration reactor) by Phanerochaete chrysosporium was studied. High activity of enzymes, especially for LiP, was obtained in the aeration reactor. The production of enzymes and decoloration of orange I were investigated in semi-continuous culture and continuous culture respectively. High activity of enzymes for a long period of time was detected in the semi-continuous culture, in which five batches of dye wastewater could be decolored to more than 90% and the specific decloration rate of orange I was above 46.7 g/(g×d) when the proportion of replacement was 1/2, while enzymes decayed rapidly and poor decoloration was gained in the continuous culture. The application of semi-continuous culture in the aeration reactor was tried for the decoloration of four batches of printing-wastewater, and the decelerations rate of the first three was all above 90%.

Fractal Model of Building Blocks for Pore Structure of Particles

MA Xing-hua; WANG Lu-ying; WAN Ming-rei; DENG Tong

. 2003, 3(5):  0-0. 

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Fluidization behaviors of gas–solid two-phase flow were studied based on experiments in a f150 mm′11500 mm standpipe under negative pressure gradient. The standpipe exit was dipped into a dense fluidization bed. The gas–solid two-phase flow in the standpipe is characteristic of flowing against negative pressure and slip velocity upward. The fluidization behaviors of the gas–solid flow in the standpipe are effected by mass flux of solid. When the mass flux of solid is less than 200~250 kg/(m2.s), there are two fluidization regimes coexisting in the standpipe, i.e., the upper dilute-phase flow and bottom dense-phase flow with gas flowing upward. When the mass flux of solid is more than 200~250 kg/(m2.s), there is only one dense-phase conveying regime in the standpipe with gas flowing downward. The particles flowing down is a decelerate process in the standpipe and the slip velocity decreases as mass flux of solid increases.

Portable X-ray Photography of Solid Concentration in Gas–Solids Fluidized Beds — (I) Principle and Image Processing

ZHANG Zhi-pan; LIU Hui-e; LUO Guo-hua; WANG Zhan-wen; WEI Fei

. 2003, 3(5):  0-0. 

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The wetting ability of the solution of water-soluble cationic polymer NCP and the solution of HPAM (partial hydrolytic polyacrylamide) on the surface of Ca-montmorillonite was determined by a JF99A contact angle calcimetre. The former has a smaller contact angle than the latter. The results of relative wetting angle show that NCP has better hygroscopicity. On the other hand, when montmorillonite was saturately adsorbed by NCP and HPAM solutions and was disposed by filtrating, washing, drying and sieving, the results of contact angle in water solution show that the NCP–MT has better hygroscopicity than HPAM–MT.

Simulation on the Conductivity of Charging Stock with Percolation Structure in the Submerged Arc Furnace

CHU Shao-jun;NIU Qiang;LIU Xin-yu;WANG Xin

. 2003, 3(5):  0-0. 

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Thiobacillus ferrooxidans oxidating ferrous sulphate effectively at low pH (pH<2.0) is prerequisite to the industrial application of two-step bioleaching. In this work, the strain was adapted by sequential adaptive culture and isolation via continuous culture. Compared with the original Thiobacillus ferrooxidans TF5, its optimum pH for oxidating ferrous iron was changed from 2.0~3.0 to 1.7~2.0, and the ratio of oxidized ferrous iron was improved from 13.1% to 85% at pH=1.7. Kinetic research showed that, under the optimized cultural condition of initial pH=1.7, culture temperature near 31oC, 98% of ferrous iron contained in 9K medium was oxidized after cultivation for 52 h in a 250 ml Erlenmeyer flask incubated on a rotary shaker at 120 r/min, and the growth rate of Thiobacillus ferrooxidans cells was 0.0635 h-1, which is similar to the original type. It was showed that the adapted Thiobacillus ferrooxidans is potentially useful in the industrial application of two-step bioleaching.

Phase Transition and Transition Temperature Hysteresis of VO2 Thin Film

HU Zai-yong; XU Chu-shao; YANG Shao-li; CHEN Guang-bi

. 2003, 3(5):  0-0. 

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The VO2 thin film was prepared by the colloid method with industrial V2O5 as raw material. The properties of the VO2 film such as resistance abrupt drop temperature, phase transotion temperature hysteresis are examined. The results show that the VO2 thin film phase transition temperature is 35oC. Preparation method and substrate show greater effect on resistance abrupt change order, which can reach 2~3 order if common glass or quartz glass were employed in underlay by H2 reduction process, while it can reach 1.5~2 order of magnitude by N2 thermal decomposition. The resistance abrupt change order of magnitude is larger for VO2 film with quartz glass as substrate, the transition temperature hysteresis is 1~6oC, and closely related with the resistance abrupt change order, underlay, substrate and preparation method.

Propagation and Decay of Concentration Wave in the Liquid–Solid Pulsed Fluidized Beds

JIN Guo-dong; LIU Da-you; SHU Chi-wang

. 2003, 3(5):  0-0. 

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The propagation and decay of concentration wave in liquid–solid pulsed fluidized beds is studied by numerical simulation and experimental validation. When the semi-on period and semi-off period are much longer than the particle relaxation time, the difference between the inertia forces of the two phases is small compared with the gravity of the solid phases except a short period in the order of the particle relaxation time after a sudden change of fluidizing velocity, the momentum equations of the two phases in pulsed fluidized beds can be simplified to a local equilibrium model. The simulation difficulty caused by the ill-posedness of the basic two-fluid model can be avoided using the concentration wave equation. The liquid–solid flow pulsation induced by the fluidizing fluid varying in both sinusoidal and step-wise patterns is simulated using the five order WENO scheme for spatial derivative and three order TVD Runge–Kutta method for time derivative. The front-fixing method is used to handle the moving upper boundary. The simulation result of fluidizing velocity varying in step-wise pattern is validated and matches the experimental data well. In the pulsed fluidization, the concentration wave decays due to the interaction between the concentration discontinuity and dilatation waves.

Treatment of Coking Wastewater Using the Micro-electrolysis-SBR Activated Sludge Process

ZHANG Wen-yi

. 2003, 3(5):  0-0. 

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Challenges and opportunities to antibiotics are reviewed. Antibiotics, which have greatly enhanced human health, now are facing the issue of drug resistance of pathogen microbes and newly found diseases. However, modern biotechnology, including genomics, proteomics, bioinformatics and bio-macromolecular crystallization, is providing new ideas and methodology for the research and development of new pharmaceuticals.

Investigation of Surfactant–Stain–Metal Interaction: Naphthochrome Green/Cetyltrimethylammonium Bromide/Rare Earths Ternary Complexation

ZHENG Li-xin;SHEN Rong;GAO Hong-wen

. 2003, 3(5):  0-0. 

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The solubility of the three component system H3BO3–NaCl–MgCl2–H2O at 25 and 100oC has been measured. On the basis of the phase diagram constructed, the process technology of producing H3BO3 by hydrochloric acid decomposition from certain Ulexite in Tibet has been analyzed.

Production of Citric Acid from Apple Pomace Enzymolyzed by Cellulase

SONG Ji-rong;HUANG Jie;XU Kang-zhen;ZHAO Qiao-yun

. 2003, 3(5):  0-0. 

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Cellulase can evidently increase the content of glucose and has a significant effect on the production of citric acid from apple pomace by Aspergillus niger. Based on experiments, a cellulolytic enzyme named cellulase A6 was found able to produce about 170 g glucose from 1 kg dried apple pomace after 12 h reaction, with cellulase concentration of 20 U/g in the medium at 50oC, natural pH without pretreatment of alkali. Using the treated apple pomace as a liquid state substrate, Aspergillus niger-C selected out was able to produce about 256 g citric acid from 1 kg dried apple pomace at 35oC in 3 d or 30oC in 5 d with flask rotation speed of 210 r/min, and the conversion of citric acid could reach 80% based on the amount of sugar consumed.

Cultivation of Dunaliella salina in an Airlift Photobioreactor

HAO Jian-xin; CONG Wei; KANG Rui-juan; CAI Zhao-ling

. 2003, 3(5):  0-0. 

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The separation property of membrane is related to the aperture structure of the membrane. In this paper, the chitosan ultrafiltration (UF) membrane was immersed into a coagulation bath with proper concentration and temperature and its aperture structure was modified. The results showed that the retention rate of chitosan membranes increased by 83.7% after being treated by precipitation. The retention rate, flux and aperture structure of chitosan membranes were affected by temperature of the coagulation bath, concentration of gelating agents and time of immersion precipitation. It is necessary to select appropriate parameters to enhance the separation property of chitosan UF membrane.

Experimental Observation on Cellulosic Biodegradation in Solid State Fermentation

ZHOU Xiao-hong; CHEN Hong-zhang; LI Zuo-huo

. 2003, 3(5):  0-0. 

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Expression of human Pro-urokinase gene in Pichia pastoris and the influence of main variables on the production and expression of Pichia pastoris were investigated. pH in the growth phase was 5.6, pH in the expression phase was 6.0, and the temperature was always 28oC. It is found that there exists clear corresponding between the AOX and Pro-UK production in the fermentation process, and a new procedure by feeding methanol and glycerol alternatively was proved to be effective in improving the enzyme activity of Pro-UK in the fermentation broth.

Kinetics of Reduction of Sodium Chlorate with Sulfur to Produce Chlorine Dioxide

PENG Qing-jing; FU Wei-chang; PENG Liang-bin

. 2003, 3(5):  0-0. 

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As-containing gold ore and Mn-containing silver ore were leached simultaneously in sulfuric acid solution. The process was intensified by ultrasonic wave to resolve FeAsS and MnO2. Experiments showed that under the conditions of ultrasonic wave, As-containing gold ore/Mn-containing silver ore=1:1.3, vitriol consistency of 0.57 mol/L, reaction temperature 95oC, the resolution rate of FeAsS was 84.9%. And increasing the decomposition rate of FeAsS is very important to achieving higher leaching rate of gold.

Review on Facilitated Transport in Fixed Site Carrier Membranes

SHI Wei; ZHANG Feng-bao; ZHANG Guo-liang; ZHANG Gang

. 2003, 3(5):  0-0. 

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Facilitated transport membrane with fixed site carriers is an attractive topic in the separation of gas and liquid mixtures because it is capable of increasing permeability and permselectivity simultaneously. In this paper, the mechanism of facilitated transport in fixed carrier membranes is addressed, the methods of carriers fixation are discussed and the problems to the development of the membrane process are summarized. In addition, the prospect of facilitated transport in fixed carrier membranes is previewed.

Preparation of Mesopore Activated Carbon from Municipal Solid Organic Wastes

XIE Li-ping; LIN Wei-gang; YANG Xue-min

. 2003, 3(5):  0-0. 

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In gaseous products of biomass steam gasification, there exist a lot of CO, CH4 and other hydrocarbons that can be converted to hydrogen through steam reforming reactions. There exists potential hydrogen production from the raw gas of biomass steam gasification. In the present work, the characteristics of hydrogen production from biomass steam gasification were investigated in a small-scale fluidized bed. In these experiments, the gasifying agent (air) was supplied into the reactor from the bottom of the reactor and the steam was added into the reactor above biomass feeding location. The effects of reaction temperature, steam to biomass ratio, equivalence ratio (ER) and biomass particle size on hydrogen yield and hydrogen yield potential were investigated. The experimental results showed that higher reactor temperature, proper ER, proper steam to biomass ratio and smaller biomass particle size will contribute to more hydrogen and potential hydrogen yield.

Self-assembly Mechanism and Defect Analysis of Colloidal Silica Photonic Crystals

ZHAO Xiao-feng;ZHANG Hui;TANG Qing

. 2003, 3(5):  0-0. 

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Colloidal silica photonic crystals were prepared by using ethanol as medium. Nanospheres with a mean diameter of 238 nm and standard deviation 5.7% were obtained under strictly controlled conditions by using the improved Stober method. In this method, ethanol was proved a better medium than water and the prepared photonic crystals had fewer defects. The diffraction to incident infrared light obeyed the Bragg equation. The formation mechanism and defect formation of colloidal photonic crystals were also discussed.

Effects of He-Ne Laser Irradiation on the Mutagenesis of Beauveria bassiana

YANG Ge; CHEN Hong-zhang; LI Zuo-hu

. 2003, 3(5):  0-0. 

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CaCO3 uniform nanoparticles with particle size of 10~30 nm were synthesized in quaternary W/O microemulsion solution containing Triton X-100, cyclohexane and n-pentanol. The reaction conditions were optimized on the basis of investigation of the influence of the ratio of water to surfactant, the concentration of reactants and the ageing time on the products. Transmission electron microscopy (TEM) was utilized to characterize the shape and size of the obtained nanoparticle products.

Application of Experimental Design to Optimizing the Medium of Nuclease P1

XU Zheng-jun; XIAO Lin-ping;LU Hao;XIE Ning-chang; YING Han-jie

. 2003, 3(5):  0-0. 

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Experimental design was employed to study the effects of several factors on the production of nuclease P1 by Penicillium citrinum M02, such as carbon source, nitrogen source, phosphor source and corn steep liquor which acted as complementary nitrogen source. The results of two experiments showed that corn steep liquor could remarkably promote the production of nuclease P1. In addition, one model that can describe the fermentation perfectly was gained from these experiments. When nuclease P1 was produced on the optimized medium calculated from this model, its yield was 648.3 U/ml that is comparable with 661 U/ml from the model. And it is improved by 70% compared with the 380 U/ml, which was gained on the original medium at the same time. The possible reason for corn steep liquor promoting nuclease P1 fermentation is that corn steep liquor contains more useful amino acids such as glycin, alanine, serine and so on.