Advanced Materials Research Vols. 236-238

Abstract: Methyl 15-hydroxy-pentadecanate,which was made from malana oleifera chum oil, was an ideal material to synthesize cyclopentadecanolide-an important macrocycle musk with wide applications in fields of perfume, cosmetic, food, medical and etc..One kind of screened lipase from Candida sp.GXU08 strain was used to catalyze the synthesis of cyclopentadecanolide from methyl 15-hydroxy-pentadecanate. Traditionally, the catalytic reaction went on under organic system, while an ultrasonic technology was innovatively used in water/organic biphasic system to systhesize cyclopentadecanolide and received good catalytic effect. Both organic and biphasic systems had the same optimal conditions as: substrate concentration 8 mmol/L, T=40 °C, ω=180 r/min,pH=6.0-6.5,and using lipase and reaction system twice would greatly increase the production of cyclopentadecanolide. It showed that the maximum production of cyclopentadecanolide was 47.77×10^-3mg/U in biphasic system under the optimal conditions,which was 3.285 times of that in organic system. It would save the process of freeze drying and improve the production of cyclopentadecanolide. It verified that methyl 15-hydroxy-pentadecanate would directly cyclize into cyclopentadecanolide in organic system. While in biphasic system,it would hydrolysis into 15-hydroxypentadecanoic acid firstly, and then cyclized into cyclopentadecanolide.

Abstract: In bioreactor, it often monitors some procedure parameters such as temperature, pH , and dissolved oxygen values to monitor fermentation process, but these parameters may be instability and delayed. Calorimetry hasn’t distinctiveness, virulence and doesn’t be sensitive to electrochemistry. So it can be used in some kind of culture fluid, even so it can be used in muddy fluid that photometers can’t be used in. Relative to other monitoring ways, calorimetry’s response time is short, so calorimetry is well suited to monitor bioprocesses on line. Calorimetry only needs normal standardize monitoring units, and this normal standardize monitoring units is be widely used in industry. Calorimetry as a simple alternative is beginning to be used in monitor bio-fermentation process.

Abstract: The changes of cell membrane permeability caused by dimethyl sulphoxide (DMSO) and ethanol, two commonly used solvents in study of water-insoluble elicitors, were investigated in suspension cultures of Taxus cuspidata. The extracellular medium became alkalinized in the case of DMSO while the medium pH fluctuated upon the addition of ethanol. When the content of DMSO or ethanol was larger than 2% (v/v), the concentration of intracellular malonyl dialdehyde (MDA) increased remarkably at day 5 compared to that of the control, while that of the extracellular MDA less changed at a DMSO content of below 2% (v/v) and increased rapidly within 15 min at a DMSO content of 4% (v/v). The electrical conductivity (EC) decreased slightly when DMSO content was below 2% (v/v) but increased markedly at day 5 when DMSO content reached 4% (v/v). EC less varied when the content of ethanol was below 0.4% (v/v) but changed obviously when the ethanol content was larger than 1% (v/v). The cell membrane integrity hardly broke in the case of small concentration of DMSO (below 1%, v/v), but the presence of even small amount of ethanol (0.4%, v/v) caused cell membrane integrity lost partly, especially long time contact. It is thus concluded that DMSO is a more suitable solvent for water-insoluble elicitors compared to ethanol especially at low concentration levels.

Abstract: The upflow anaerobic immobilized microbe reactor of the anaerobic ammonium oxidation process (ANAMMOX) was used in treatment of high nitrogen concentration organic wastewater, which was made to study the effect of synergistic nitrogen removal by ANAMMOX–denitrification. The experimental results showed that the mass concentrations of NH ₄⁺-N and NO － 2-N in the influent had no obvious influence on the synergistic nitrogen removal in opportune range. When the mass concentrations of NH ₄⁺-N and NO_－2-N in the influent were kept at 301-800 mg/L, the removal rates of NH ₄⁺-N, NO_－2-N and TN were 93.3 %, 98.6 % and 90.3 % respectively. When the influent COD was kept at 800-850 mg/L, COD had almost no influence on the synergistic nitrogen removal, and the removal rate kept at 95.7％. Meanwhile, the characteristic changes of NO_－3-N, N₂, pH value and organism proved that the synergism was in a good state. Introduction

Abstract: In this research, cage-shape macroporous/mesoporous three-dimensional-ordered material (3DOM) SiO₂ was prepared using polystyrene colloidal crystal (PS) as template and TEOS as silica source, in which papain was immobilized. The optimal immobilization, the stability and the application of the immobilized papain were studied. Compared with the free papain, the immobilized papain exhibits higher activity. The thermal and pH stability of the immobilized papain obviously improved.

Abstract: The reaction process of methanol to hydrocarbons was studied by means of in situ FTIR spectroscopic technique. The interaction between methanol and HZSM-5 surface was determined under different reaction conditions. It was found that the Lewis acid sites on the HZSM-5 surface played an important role in the conversion of methanol to hydrocarbons. During the catalysis process, methanol was adsorbed on the Lewis acid sites through chemical bond which was stronger than the interaction between methanol and the Brønsted acid sites. The dehydration of methanol took place on the Lewis acid sites to form the intermediate, dimethyl ether. According to the experimental results, the elaborate mechanism of methanol to hydrocarbons conversion was discussed.

Abstract: Ceramic-supported manganese dioxide catalyst, MnO2-ceramic, prepared by impregnation- precipitation method and calcined at 350 degree C, was exposed to flue gases to investigate the catalytic oxidation of sulphur dioxide in flue gas at seawater buffering system. The results showed that compared with acid treated ceramic, MnO₂-ceramic gained 2%-46% higher Desulfurization efficiency in temperature range of 15-75 degree C. MnO₂-ceramic exhibited 57% desulfurization efficiency at its favorable temperature (60 degree C) while ceramic showed 11% Desulfurization efficiency at 60 degree C. MnO₂-ceramic was found to catalyze S(IV)oxidation even at low pH (pH<4) while the reaction rate of noncatalytic S(IV) oxidation is negligible under the identical conditions. No catalytic activity decay was observed after 40 hours’ run. XPS reveals that the Mn was in the oxidation state of +4 for the MnO_x-ceramic. SEM-EDS and XRD indicated that the good catalytic activity of MnO₂-ceramic at low temperature could be attributed to high dispersion of MnO₂ on ceramic support. The high performance of MnO₂-ceramic on the SO₂ removal appeared to be promising in the seawater flue gas desulfurization industrial application when high sulfur coals were burned.

Abstract: Compared with Thermus thermophilus HB8 xylose isomerase(TthXI), the increase of the substrate specificity on D-xylose of its N91D mutant (TthXI-N91D) was observed in the previous study. In order to clarify the structural mechanism of TthXI-N91D, the complex model of TthXI with D-xylose was constructed by molecular docking method. The TthXI-N91D homology model was built by WATH IF5.0 based on the above complex. The results indicate that the distance between the conserved residue H53 NE2 and D-xylose O5 has decreased in 0.083 nm in the TthXI-N91D active site. The short distance is propitious to transfer the hydrogen atom during the open ring process of substrate. At the same time, the distance between the conserved residue T89 OG1, involving in combining glucose, and D-xylose C5 has reduced 0.133 nm. The shrunken space has an unfavorable effect on accommodating the larger glucose than xylose, and lead to the enhanced specificity for D-xylose.The above phenomenon maybe the main reason for explaining that TthXI-N91D is easy to combine D-xylose showing enhanced specificity. The results paly an important role in understanding the catalytic mechanism of xylose isomerase and provides the base for its molecular design.

Abstract: Xylanase (E.C 3.2.1.8) is a widespread group of enzyme which can catalyze the endohydrolysis of 1, 4-β-D-xylosidic linkages in xylan. The thermostable xylanase has attracted widely attention because of its application in industrial processes. In this study, the cDNA of xylanase gene was obtained from Aspergillus niger C3486 by RT-PCR. The xylanase DNA contains a 50 bp intron through the comparison between the DNA and cDNA sequence. The thermostability of this xylanase was significantly improved by directed evolution.

Abstract: A strain S307 that can oxidize selectively (S)- 1-phenylethanol to acetophenone and a strain IS 118 that can asymmetric reduce acetophenone to (R)- 1-phenylethanol were isolated from soil. S307 was identified as a species of Undibacterium belonging to the family Oxalobacteraceae of the Betaproteobacteria. S307. IS 118 was identified as Asperillus tamarii. The oxidation of (R, S)-1- phenylethanol with Undibacterium sp. S307 followed by the reduction of the oxidation mixture with Asperillus tamarii IS 118 to afford (R)-1-phenylethanol was described. The effects of redox-coupling patterns on the product of (R)-1-phenylethanol were investigated. After redox-coupling deracemization, the yield and ee of (R)-1-phenylethanol were 87% and 99% respectively.