Production of 2-phenethyl alcohol and 2-phenyllactic acid in Candida species

2-Phenethyl alcohol (2-PEA) and 2-phenyllactic acid (2-PLA) were isolated from the culture filtrates of Candida species grown in media containing peptone or phenylalanine as nitrogen source. These compounds were characterized by comparing their UV, IR, and NMR spectral properties with authentic samples. Candida species differed markedly in their production of 2-PEA and 2-PLA. Experiments using [14C]-phenylalanine indicated that both 2-PEA and 2-PLA are synthesised from L-phenylalanine. A pathway for the biosynthesis of 2-PEA from L-phenylalanine has been proposed.

Differences in the levels of aminoacylation and contents of modified nucleotides between total tRNAs from N2- and NH4+-grown Azospirillum lipoferum cells

Total tRNAs isolated from N2- and NH4(+)-grown Azospirillum lipoferum cells were compared with respect to amino acid acceptance, isoacceptor tRNA species levels and extent of nucleotide modifications. Amino-acylation of these two tRNA preparations with ten different amino acids indicated differences in the relative acceptor activities. Comparison of aminoacyl-tRNA patterns by RPC-5 column chromatography revealed no qualitative differences in the elution profiles. However, quantitative differences in the relative amounts of some isoacceptors were observed. These results indicate that alterations of relative amounts of functional tRNA species occur to match cellular requirements of the bacterial cells using N2 or NH4+ as nitrogen source. In addition, the content of modified nucleotides in total tRNAs of N2- and NH4(+)-grown cells was determined. In the NH4(+)-grown cells, content of most of the modified nucleotides decreased significantly. Based upon these results, the relationship of chargeability of tRNAs to base modifications is discussed.

Substrate impact on the growth of InN nanostructures by droplet epitaxy

The substrate effect on InN nanostructures grown by droplet epitaxy has been studied. InN nanostructures were fabricated on Si(111), silicon nitride/Si(111), AlN/Si(111) and Ge(100) substrates by droplet epitaxy using an RF plasma nitrogen source. The morphologies of InN nanostructures were investigated by field emission scanning electron microscopy (FESEM). The chemical bonding configurations of InN nanostructures were examined by x-ray photoelectron spectroscopy (XPS). Photoluminescence spectrum slightly blue shifted compared to the bulk InN, indicating a strong Burstein-Moss effect due to the presence of high electron concentration in the InN dots.

Extraordinary supercapacitor performance of heavily nitrogenated graphene oxide obtained by microwave synthesis

Heavily nitrogenated graphene oxide containing similar to 18 wt% nitrogen, prepared by microwave synthesis with urea as the nitrogen source, shows outstanding performance as a supercapacitor electrode material, with the specific capacitance going up to 461 F g(-1).

Copper-Catalyzed Oxidative Transformation of Secondary Alcohols to 1,5-Disubstituted Tetrazoles

A mild and convenient oxidative transformation of secondary alcohols to 1,5-disubstituted tetrazoles is uncovered by employing trimethylsilyl azide (TMSN3) as a nitrogen source in the presence of a catalytic amount of copper(II) perchlorate hexahydrate Cu(ClO4)(2)(.)6H(2)O] (5mol%) and 2,3-dichloro-5,6-dicyano-para-benzoquinone (DDQ) (1.2equiv.) as an oxidant. This reaction is performed under ambient conditions and proceeds through CC bond cleavage.

Nitrite utilization by Chaetoceros muelleri under elevated CO2 concentration

Chaetoceros muelleri (Lemn.) was cultured with nitrite (NO2-) or nitrate (NO3-) as the sole nitrogen source and aerated with air or with CO2-enriched air. Cells of C. muelleri excreted into the medium nitrite produced by reduction of nitrate when grown with 100 mu M NaNO3 as nitrogen source. Accordingly, NO2- concentration reached 10.4 mu M after 95 h at the low CO2 condition (aerated with air); while the maximum NO2- concentration was only around 2.0 mu M at the high CO2 condition (aerated with 5% CO2 in air), furthermore, after 30 h it decreased to no more than 1.0 mu M. NO2- was almost assimilated in 80 h when C. muelleri was cultured at the high CO2 condition with 100 mu M NaNO2 as sole nitrogen source. At the high CO2 condition, after 3 h the activity of nitrite reductase was as much as 50% higher than that at the low CO2 condition. It was indicated that enriched CO2 concentration could inhibit nitrite excretion and enhance nitrite assimilation by cells. Therefore, aeration with enriched CO2 might be an effective way to control nitrite content in aquaculture systems.

alr0117, a two-component histidine kinase gene, is involved in heterocyst development in Anabaena sp PCC 7120

Anabaena sp. PCC; 7120 was mutagenized by transposon Tn5-1087b, generating a mutant whose heterocysts lack the envelope polysaccharide layer. The transposon was located between nucleotides 342 and 343 of alr0117, a 918 bp gene encoding a histidine kinase for a two-component regulatory system. Complementation of the mutant with a DNA fragment containing alr0117 and targeted inactivation of the gene confirmed that alr0117 is involved in heterocyst development. RT-PCR showed that alr0117 was constitutively expressed in the presence or absence of a combined-nitrogen source. hepA and patB, the two genes turned on during wild-type heterocyst development, were no longer activated in an alr0117-null mutant. The two-component signal transduction system involving alr0117 may control the formation of the envelope polysaccharide layer and certain late events essential to the function of heterocysts.

ECR plasma in growth of cubic GaN by low pressure MOCVD

To heteroepitaxally grow the crystalline cubic-GaN (c-GaN) film on the substrates with large lattice mismatch is basically important for fabricating the blue or ultraviolet laser diodes based on cubic group III nitride materials. We have obtained the crystalline c-GaN film and the heteroepitaxial interface between c-Gan and GaAs (001) substrate by the ECR Plasma-Assisted Metal Organic Chemical Vapor Deposition (PA-MOCVD) under low-pressure and low-temperature (similar to600degreesC) on a homemade ECR-plasma Semiconductor Processing Device (ESPD). In order to decrease the growth temperature, the ECR plasma source was adopted as the activated nitrogen source, therefore the working pressure of MOCVD was decreased down to the region less than 1 Pa. To eliminate the damages from energetic ions of current plasma source, a Multi-cusp cavity,coupling ECR Plasma source (MEP) was selected to use in our experiment. To decrease the strain and dislocations induced from the large lattice mismatch between c-GaN and GaAs substrate, the plasma pretreatment procedure i.e., the initial growth technique was investigated The experiment arrangements, the characteristics of plasma and the growth procedure, the characteristics on-GaN film and interface between c-GaN and GaAs(001), and the roles of ECR plasma are described in this contribution.

GaInNAs/GaAs multiple-quantum well resonant-cavity-enhanced photodetectors at 1.3 mu m

A GaInNAs/GaAs multiple quantum well (MQW) resonant-cavity enhanced photodetector (RCF-PD) operated at a wavelength of 1.3 mum with the full width at half maximum of 4nm has been demonstrated. The GaInNAs RCE - PD was grown by molecular beam epitaxy using a homemade ion-removed dc plasma cell as a nitrogen source. GaInNAs/GaAs MQW shows a strong exciton peak at room temperature, which is very beneficial for applications in long-wavelength absorption devices. For a 100 mum diameter RCE-PD, the dark current is 20 and 32 pA at biases of 0 and 6 V, respectively, and the breakdown voltage is - 18 V. The measured 3 dB bandwidth is 308 MHz, which is limited by the resistance of p-type distributed Bragg reflector mirror. The tunable wavelength in a range of 18 nm with the angle of incident light was observed.

Hydrogen contaminant and its correlation with background electrons in GaN

GaN epilayers grown by molecular beam epitaxy using NH3 as the nitrogen source were found to contain hydrogen. We further notice that the background electron concentration in GaN can be correlated with the amount of hydrogen contaminant. X-ray photoelectron spectroscopy (XPS) measurements of the N Is peak reveal that hydrogen is bound to nitrogen. This will make the corresponding Ga atom see insufficient N counterpart, as can be inferred from the XPS Ga 3d spectrum. We then think that nitrogen in the lattice terminated by hydrogen is an effective nitrogen vacancy and hence a donor accounting for the background electrons.

Isolation and Characterization of a Methomyl-Degrading Paracoccus sp mdw-1

Methomyl, an extremely toxic pesticide, is widely used in agriculture. A strain named mdw-1 capable of degrading methomyl rapidly was successfully isolated from activated sludge in this study. It could utilize methomyl as the sole carbon or nitrogen source. The optimal temperature and medium pH for its growth and methomyl biodegradation were 30 degrees C and 7.0, respectively. It was identified as a Paracoccus sp. according to its morphological features, physiological and biochemical characteristics, and phylogenetic analysis based on the sequence of 16S rDNA. Gas chromatography-mass spectrometry (GC-MS) analysis showed that methomyl could be completely transformed to S-methyl-N-hydroxythioacetamidate in 10 h of incubation with the isolate mdw-1.

3μm GaInNAs/GasAs Quantum Well Resonant Cavity Enhanced Photodetector

A 1.3μm GaInNAs resonant cavity enhanced (RCE) photodetector (PD) has been grown by molecular beam epitaxy (MBE) monolithically on (100) GaAs substrate using a home-made ion-removed dc-plasma cell as nitrogen source. A transfer matrix method was used to optimize the device structure. The absorption region is composed of three GaInNAs quantum wells separated by GaAs layers. Devices were isolated by etching 130μm-diameter mesas and filling polyamide into grooves. The maximal quantum efficiency of the device is about 12% at 1.293μm. Full width at half maximum (FWHM) is 5.8nm and 3dB bandwidth is 304MHz. Dark current is 2 * 10~(-11) A at zero bias voltage. Further improvement of the performance of the RCE PD can be obtained by optimizing of the structure design and MBE growth conditions.

1.3 mu m GaInNAs/GaAs multiple-quantum-wells resonant-cavity-enhanced photodetectors

A GaInNAs/GaAs multiple quantum well (MQW) resonant-cavity enhanced (RCE) photodetector operating at 1.3 mum with the full-width at half-maximum of 5.5 nm was demonstrated. The GaInNAs RCE photodetector was grown by molecular-beam epitaxy using an ion-removed dc-plasma cell as nitrogen source. GaInNAs/GaAs MQW shows a strong exciton peak at room temperature that is very beneficial for applications in long-wavelength absorption devices. For a 100-mum diameter RCE photodetector, the dark current is 20 and 32 pA at biases of 0 and 6 V, respectively, and the breakdown voltage is -18 V. The measured 3-dB bandwidth is 308 MHz. The reasons resulting in the poor high speed property were analyzed. The tunable wavelength of 18 nm with the angle of incident light was observed.

白腐菌选择性降解木质素的研究

对15株白腐真菌进行了以玉米秸秆为基质的初步筛选，从中获得一株选择性系数较高的菌株Y10，并对其降解玉米秸秆的情况进行了研究。结果表明，在30天的培养过程中菌株Y10对玉米秸秆降解的选择性系数都大于1，第15天选择性系数最高为3.88。对未经降解和降解过的玉米秸秆分别作了紫外光谱和红外光谱分析，结果表明，经该菌降解后玉米秸秆的化学成分发生了很大变化，且木质素的降解程度要大于纤维素的降解程度。对菌株Y10进行了ITS-5.8S rDNA序列鉴定，初步判定其为Cerrena sp.。 为了考查不同的外源添加物对菌株Y10降解玉米秸秆的影响，在以玉米秸秆为基质的固态发酵培养基中分别添加了7种金属离子、8种碳源、6种氮源。结果显示，这7种金属离子均能促进木质素的降解，并且一定浓度的某些离子明显抑制纤维素的降解；其中添加0.036%的MnSO4·H2O和0.36%的MgSO4·7H2O对纤维素降解的抑制作用比较强，降解率分别为0.96%和1.31%，木质素的选择性系数分别达到了34.40和20.17。8种碳源中除麦芽糖外都能促进木质素的降解，除微晶纤维素外都明显促进纤维素的降解。6种氮源中酒石酸铵、硫酸铵、草酸铵和氯化铵的添加都会使该菌生长变慢，而且氮源浓度越高菌丝生长越慢。外加碳源和金属离子对半纤维素降解和选择性系数的影响不大。 同时对菌株Y10在液态培养下产木质素降解酶的条件和培养基做了优化。结果表明，在初始产酶培养基中，菌株Y10的漆酶酶活在第10d达到最高，锰过氧化物酶酶活在第11d达到最高，基本上检测不到木质素过氧化物酶。菌株Y10产漆酶的最适温度为32℃，最适PH为6.0；产锰过氧化物酶的最适温度为32℃，最适PH为6.5。菌株Y10产漆酶的最佳碳源为甘露糖，最佳氮源为酒石酸铵，最适诱导剂VA浓度为3 mmol/L，最适表面活性剂TW-80浓度为1%。 利用响应面法对其产漆酶的培养基进行优化，优化后的培养基配方为葡萄糖10.00 g/L，酒石酸铵0.50 g/L，大量元素296.50 ml/L，微量元素100.00 ml/L，NTA 1.40 g/L，VA 5.00 mmol/L，吐温-80加入量为0.10%。进行了菌株Y10产漆酶的验证实验，实测酶活为5282.56 U/L，与预测酶活5162.73 U/L接近。在优化后培养基中，菌株Y10在第14 d达到生长的最高峰，第20 d时，漆酶酶活最高，为11325.00 U/L；第16 d时，锰过氧化物酶酶活最高，为30.77 U/L。 对菌株Y10的漆酶酶学性质做了初步的研究，结果显示，酶反应的最适温度为40℃-65℃，最适PH为3.0。在40℃，PH=3.0时，漆酶催化ABTS反应的米氏方程为 。 Fifteen white-rot fungi based on corn stalk were screened. One white-rot fungus Y10 with high selectivity value was obtained. The degradation of corn stalk was initially studied. The results indicated that the selectivity value was above 1 during the 30 day-cultivation and the highest was 3.88 after 15 days. The composition of untreated and treated stalk was analyzed through ultraviolet spectroscopy and infrared spectroscopy. It was found that the composition of treated stalk was greatly altered and the degree of the degradation of lignin is greater than the cellulose. Y10 was identified as Cerrena sp. by ITS -5.8S rDNA sequence analysis. The influence of metal ions, carbon sources and nitrogen sources on corn stalk degradation by white-rot fungus was studied. While all seven metal ions could promote lignin degradation, the cellulose degradation was best inhibited at certain ion concentrations. Notably, when 0.036% MnSO4·H2O and 0.36% MgSO4·7H2O were added into the medium, the cellulose degradation was restrained to the extents that the coefficients of lignin selectivity rose to 34.40 and 20.17 respectively. It was also found that all carbon sources except maltose can promote lignin degradation. The addition of carbon sources other than microcrystalline cellulose significantly promoted cellulose degradation. The addition of the nitrogen sources, ammonium tartrate, ammonium sulfate, oxalate, ammonium chloride, resulted in remarkable inhibition to mycelium growth; the larger the concentrations of nitrogen sources are, the slower the mycelium grew. The addition of carbon sources and metal ions had less impact on the degradation of hemicellulose and selectivity value. Meanwhile, we optimized the conditions and culture medium of the lignin-degrading enzyme production of strain Y10. The results showed that in the initial culture medium, the Lac activity was highest at the 10th day, the MnP activity was highest at the 11th day and the LiP could not be detected. The optimum condition of Lac was at temperature 32 and PH =6.0 and the optimum condition of MnP was at temperature 32 and PH =6.5. The optimum carbon source for Lac was seminose, the optimum nitrogen source was ammonium tartrate, the optimum content of VA was 3 mmol/L, the optimum content of TW-80 was 1%. PB and RSM were used to optimize the culture medium of laccase by white-rot fungus Y10. The optimum culture medium was consist of glucose 10.00 g/L, ammonium tartrate 0.50 g/L, macro elements 296.50 ml/L, trace elements 100.00 ml/L, NTA 1.40 g/L, VA 5.00 mmol/L, TW-80 0.10%. Under the optimal conditions, the activity of laccase was 5282.56 U/L and the experimental value agreed with the predicted value 5162.73 U/L. The biomass was highest at the 14th day, the Lac activity was highest at the 20th day, the MnP activity was highest at the 16th day. The results of the studies on the characteristics of Lac showed that the optimum temperature for Lac activity is 40℃-65℃ ; the optimum PH for Lac activity is 3.0 and under 40℃，PH=3.0, the Michaelis-menten equation of Lac catalized ABTS oxidation was .

厌氧复合菌系的筛选及含纤维素原料预处理复合菌剂的研究

本文从不同厌氧生境中获得7组(C-2、Y-2、L-2 、NZ、H-3、CZ、L-3)具有纤维素降解能力的复合菌系。经过不断传代、淘汰纤维素降解能力降低的菌系，最后得到一组高效、传代稳定的厌氧纤维素分解复合菌系L-3。该菌系可使滤纸在42 h内溃烂，并能在分解纤维素的同时产氢气。对L-3复合菌系的产酶条件进行了研究，结果表明，在实验范围内该菌系的产酶最适条件为：pH 6.5，温度37 ℃，接种量5 %，最佳碳源为滤纸，最佳氮源为硫酸铵。第10天测得羧甲基纤维素酶(CMCase)、滤纸酶(FPA)、外切葡聚糖酶(C1)、β-葡聚糖苷酶(β-glucodase)的酶活分别为0.216 U/ml、0.101 U/ml、0.132 U/ml、0.002 U/ml，滤纸失重率70.6 %。发酵代谢产物乙醇和丁酸含量分别可达1378 mg/L 、2695 mg/L，发酵产生的气体中氢气含量最高可达70.2 %。DGGE结果表明该菌系主要由14种菌组成，其中有三株菌在发酵前后菌数发生了明显的变化，说明在以滤纸为底物的降解过程中，这三株菌起到了重要作用，对这三株菌进行了分子生物学鉴定，初步定为Clostridium phytofermentans、Clostridium cellulovorans、Desulfovibrio sp。 利用实验室分离得到的纤维素降解菌，最终配制出由10、X-1、X-13、ST-13、L-3组成的好氧-厌氧纤维素降解复合菌剂。以秸秆为发酵底物，菌剂接种量1%，利用复合菌剂预处理后的秸秆，发酵总产气量相对于对照提高了71.62%，甲烷含量最高可达70.08%。 A group of microbial consortia L-3 was isolated from the anaerobic fermentation residue of corn stalk, which could degrade cellulose and produce hydrogen. The CMCase, FPA, C1 and β-glucosidase activity of L-3 could reach to 0.216 U/ml, 0.101 U/ml, 0.132 U/ml and 0.002 U/ml, respectively. In the filter degrading process, the filter paper collapsed in the liquid culture within 42 h and the filter degrading rate could reach to 70.6% in the 13 days, meanwhile, hydrogen was determined and the highest hydrogen content was 70.2%. The optimum cellulase-degrading conditions were filter papaer as the carbon source, (NH4)2SO4 as the nitrogen source, 37 ℃ and pH 6.5 in this experiment. DGGE results showed that the microbial consortia L-3 mainly included 14 strains. The amount of 3 strains were changed during the fermentation. These strains were identified as Clostridium phytofermentans、Clostridium cellulovorans、Desulfovibrio sp by 16S rDNA sequence analysis. The cellulose- degrading microbial agent was composed by 10, X-1, X-13, ST-13, L-3 which were isolated in the laboratory. The straw pretreated by cellulose-degrading microbial agent was used to ferment, the total biogas production increased by 72% comparing to the control. The content of methane could reach to 70.08%。