提高木糖代谢能力的酿酒酵母Y5-X3的初步构建

为获得能够发酵木糖和葡萄糖的新菌种,文中采用实验室专利菌株Saccharomyces cerevisiae Y5为宿主菌,分别采用热带假丝酵母(Candida tropicalis)和休哈塔假丝酵母(Candida shehatae)作为木糖代谢关键酶XYL1,XYL2的来源,利用酵母整合载体将XYL1,XYL2基因导入S.cerevisiae Y5基因组,同时超表达S.cerevisiae Y5内源木酮糖激酶基因XKS1,获得了酿酒酵母新菌种S.cerevisiae Y5-X3。结果表明,S.cere-visiae Y5-X3在摇瓶共发酵3%葡萄糖和2%木糖时能够利用木糖产乙醇,木糖消耗量和乙醇产量分别比宿主菌提高102.93%和12.54%,发酵2%木糖时木糖的消耗量是宿主菌的2.7倍。XKS1基因的超表达促进了木糖代谢,大大减少了木糖醇积累,提高了乙醇产量。     

热带假丝酵母用未脱毒汽爆玉米秸秆产乙醇研究

为阐明专利菌种Candida tropicalis Y1利用玉米秸秆产乙醇的能力,以未脱毒汽爆玉米秸秆为原料进行分步糖化发酵(SHF)及同步糖化发酵(SSF)产乙醇。研究结果表明,底物浓度为25%(w/v)、纤维素酶15FPU/(g底物)、纤维二糖酶Novozyme 188 20IU/(g底物)、接种量5%(v/v)及不需添加任何外源营养物质,该菌在SHF过程中的乙醇浓度为38.75g/L乙醇,为理论产率的77.9%,在SSF过程中的乙醇浓度为40.53g/L;同时,SSF与SHF相比,SSF可得到更多的木糖醇,且毒性物质乙酸的浓度维持在较低水平。说明该专利菌株不但有较强的耐发酵抑制剂的能力,而且有较好的代谢葡萄糖和木糖分别产乙醇和木糖醇的能力。     

固体酸和两相反应体系对糠醛制备的影响

糠醛是一种重要的生物质基平台化合物,在医药、农药、橡胶和石油炼制等领域有着广泛的应用,其开发具有广阔的市场前景。目前,糠醛的制备主要是以生物质中的半纤维素为原料,经过解聚和脱水反应获得。本文综述了以生物质及木糖为原料催化制取糠醛的反应机理,以及采用不同固体酸催化剂和反应溶剂体系生产糠醛的研究进展,为利用生物质生产糠醛提供技术参考。     

磁性碳基固体酸催化剂的制备及其水解工艺优化研究

采用共沉淀法合成磁性Fe₃O₄,通过碳化磺化制备核壳结构的磁性固体酸催化剂Fe₃O₄/C-SO₃H,并利用透射电子显微镜(TEM)、傅里叶变换红外光谱仪(FT-IR)、X射线衍射(XRD)、振动样品磁强计(VSM)、元素分析等手段对催化剂特性进行表征分析。以催化玉米芯水解所得的木糖得率为评价指标,对磁性固体酸催化剂催化玉米芯水解工艺条件进行优化研究,得出最佳条件为反应时间10 h、反应温度140℃、催化剂用量1.5 g、固液比(g/mL)2∶50(玉米芯含量为0.5 g),此时木糖得率为51.01%。研究认为,磁性固体酸催化剂催化木质纤维素水解的反应过程为酸催化和吸附过程共同作用,木质纤维素是分级解聚逐步转化,利用两步操作能够最大程度的水解木质纤维素。     

响应面法对磁性碳基固体酸催化剂的制备工艺优化研究

为使磁性碳基固体酸催化剂具有更好的催化活性和水热稳定性,利用响应面法对其制备工艺进行优化,以催化玉米芯水解所得的木糖得率为评价指标,选取碳化温度、碳化时间、磺化温度和磺化时间4个显著影响的因素,设计四因素三水平Box-Behnken试验,考察各因素对制备催化剂的影响,并确定最优制备工艺条件。实验结果表明,建立的二次多项式数学模型显著性较高(p=0.0003),相关系数R~2=0.8839,对实验结果具有较好的预测性。在优化的基础上确定磁性固体酸催化剂的最佳制备工艺条件为:碳化温度455℃、碳化时间4.8 h、磺化温度107℃和磺化时间10.0 h。在此条件下制备的磁性固体酸催化剂催化水解玉米芯所得木糖的得率为39.35%,与模型预测值38.73%有1.60%的误差,说明用此模型来优化磁性固体酸催化剂的制备工艺是合理的。同时,将制备的磁性固体酸催化剂与SBA-15、HZSM-5、Amberlyst-15这3种常见固体酸催化剂对催化玉米芯水解的木糖得率进行比较,结果表明,磁性固体酸催化剂的活性最高,研究价值突出。通过研究,明确制备过程中各因素对磁性碳基固体酸催化剂催化活性和水热稳定性的影响情况,可为后续催化剂设计、改性、载体选择等方面提供理论依据和实验基础。     

代谢木糖重组酿酒酵母的初步构建

为使酿酒酵母(Saccharomyces cerevisiae)代谢木糖产乙醇,须要在酿酒酵母胞内表达木糖代谢途径的关键酶基因--木糖还原酶基因xyl1和木糖醇脱氢酶基因xyl2,这2种酶基因的相对表达水平对乙醇的产生和木糖醇的积累具有重要影响.该研究初步构建了含有诱导型启动子控制的木糖还原酶基因xyl1的酵母表达载体pYes2-xyl1和含有组成型强启动子控制的木糖醇脱氢酶基因xyl2的酵母表达载体pDR195-xyl2,同时,在国内首次克隆出热带假丝酵母(Candida tropicalis)的木糖醇脱氢酶基因.这2个表达载体的构建为后续重组酵母的构建提供了重要基础.     

微波辐照玉米芯水解制取木糖的研究

考察了微波辐照水解玉米芯制备木糖的新工艺.通过单因素试验和正交试验,确定了最佳微波辐照反应条件,并与传统蒸煮法制木糖工艺进行了对比.试验结果表明:以1.25%硫酸为催化剂,固(玉米芯)液(水)比为1:15,在微波反应器内于:140℃水解15min,可获得高还原糖及木糖得率,分别为95.33%和71.48%,同时副产物糠醛的转化率为3.07%.通过对水解过程的动力学研究,表明在微波辐照下玉米芯中半纤维素转化为木糖的反应速率大于传统蒸煮法,验证并说明了微波处理所需时间更短,效率更高.     

填料型固体酸催化剂AAO/SBA-15-SO3H的制备及其在催化木糖制糠醛中的活性研究

以多孔阳极氧化铝(AAO)为基体,采用直接法和后合成法制备填料型固体酸催化剂AAO/SBA-15-SO3H。用红外光谱法分析催化剂制备过程中表面基团的变化,结果表明,两种方法制备的催化剂均含有质子酸中心-SO3H。SEM和TEM结果表明SBA-15在AAO介孔结构中呈柱状垂直基体生长。催化木糖脱水制糠醛实验表明直接法制备的催化剂具有较高的催化活性,木糖转化率可达90%以上,催化剂选择性达到74%。超声振动法表明直接法制备的填料型催化剂具有较好的机械附着稳定性,在40kHz频率下超声1h后催化剂质量减少不到5%。活性再生实验表明使用H2O2再生后催化剂活性能够基本恢复。     

重组酿酒酵母发酵木糖产乙醇的研究进展

木糖发酵是利用木质纤维素原料制取乙醇商业化生产的基础和关键,但传统的乙醇生产菌株酿酒酵母(Saccharomyces cerevisiae)不能利用木糖,因而无法满足商业生产的需求.人们利用各种基因工程手段对S. cerevisiae实施基因改造,包括对木糖运输途径的改造,木糖代谢途径的引入,增强其对发酵抑制剂的耐受性等方面都得到广泛研究,各重组菌的木糖发酵能力有了不同程度的改善,但是仍然未能用于商业化生产.酿酒酵母的木糖代谢工程有待于进一步深入研究.     

乙醇发酵重组大肠杆菌的构建——运动发酵单胞菌pdc基因在大肠杆菌中的高效表达

为了使大肠杆菌代谢葡萄糖和木糖产乙醇,将运动发酵单胞菌乙醇发酵途径中的关键酶基因丙酮酸脱羧酶基因与质粒载体pGM-T连接转化至大肠杆菌TOP10中。丙酮酸脱羧酶基因在T7启动子的启动下得到了高效表达。构建的重组大肠杆菌不但能利用葡萄糖也能利用木糖产乙醇,在葡萄糖和木糖同时存在时,优先利用葡萄糖。     

Ash-forming elements in four Scandinavian wood species. Part 1: Summer harvest

Woody biomass in Finland and Sweden comprises mainly four wood species: spruce, pine, birch and aspen. To study the ash, which may cause problems for the combustion device, one tree of each species were cut down and prepared for comparisons with fuel samples. Well-defined samples of wood, bark and foliage were analyzed on 11 ash-forming elements: Si, Al, Fe, Ca, Mg, Mn, Na, K, P, S and Cl. The ash content in the wood tissues (0.2–0.7%) was low compared to the ash content in the bark tissues (1.9–6.4%) and the foliage (2.4–7.7%). The woods’ content of ash-forming elements was consequently low; the highest contents were of Ca (410–1340 ppm) and K (200–1310), followed by Mg (70–290), Mn (15–240) and P (0–350). Present in the wood was also Si (50–190), S (50–200) and Cl (30–110). The bark tissues showed much higher element contents; Ca (4800–19,100 ppm) and K (1600–6400) were the dominating elements, followed by Mg (210–2400), P (210–1200), Mn (110–1100) and S (310–750), but the Cl contents (40–330) were only moderately higher in the bark than in the wood. The young foliage (shoots and deciduous leaves) had the highest K (7100–25,000 ppm), P (1600–5300) and S (1100–2600) contents of all tissues, while the shoots of spruce had the highest Cl contents (820–1360) and its needles the highest Si content (5000–11,300). This paper presented a new approach in fuel characterization: the method excludes the presence of impurities, and focus on different categories of plant tissues. This made it possible to discuss the contents of ash element in a wide spectrum of fuel-types, which are of large importance for the energy production in Finland and Sweden.     

NEXT GENERATION ENGINEERED MATERIALS FOR ULTRA SUPERCRITICAL STEAM TURBINES

正1 ABSTRACT To reduce the effect of global warming on our climate,the levels of CO2emissions should be reduced.One way to do this is to increase the efficiency of electricity production from fossil fuels.This will in turn reduce the amount of CO2emissions for a given power output.Using US practice for efficiency calculations,then a move from a typical US plant running at 37%efficiency to a 760℃/38.5 MPa(1 400/5 580 psi)plant running at 48%efficiency would reduce CO2emissions by 170kg/MW.hr or 25%.     

Contents in Volume 23,2014

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Aerodynamic performance effects of leading-edge geometry in gas-turbine blades

The purpose of this paper is to illustrate the advantages of the direct surface-curvature distribution blade-design method, originally proposed by Korakianitis, for the leading-edge design of turbine blades, and by extension for other types of airfoil shapes. The leading edge shape is critical in the blade design process, and it is quite difficult to completely control with inverse, semi-inverse or other direct-design methods. The blade-design method is briefly reviewed, and then the effort is concentrated on smoothly blending the leading edge shape (circle or ellipse, etc.) with the main part of the blade surface, in a manner that avoids leading-edge flow-disturbance and flow-separation regions. Specifically in the leading edge region we return to the second-order (parabolic) construction line coupled with a revised smoothing equation between the leading-edge shape and the main part of the blade. The Hodson–Dominy blade has been used as an example to show the ability of this blade-design method to remove leading-edge separation bubbles in gas turbine blades and other airfoil shapes that have very sharp changes in curvature near the leading edge. An additional gas turbine blade example has been used to illustrate the ability of this method to design leading edge shapes that avoid leading-edge separation bubbles at off-design conditions. This gas turbine blade example has inlet flow angle 0°, outlet flow angle −64.3°, and tangential lift coefficient 1.045, in a region of parameters where the leading edge shape is critical for the overall blade performance. Computed results at incidences of −10°,   −5°,   +5°,   +10° are used to illustrate the complete removal of leading edge flow-disturbance regions, thus minimizing the possibility of leading-edge separation bubbles, while concurrently minimizing the stagnation pressure drop from inlet to outlet. These results using two difficult example cases of leading edge geometries illustrate the superiority and utility of this blade-design method when compared with other direct or inverse blade-design methods.     

Hydrogen production by steam-gasification of carbonaceous materials using concentrated solar energy – V. Reactor modeling,optimization, and scale-up

A chemical reactor for the steam-gasification of carbonaceous particles (e.g. coal, coke) is considered for using concentrated solar radiation as the energy source of high-temperature process heat. A two-phase reactor model that couples radiative, convective, and conductive heat transfer to the chemical kinetics is applied to optimize the reactor geometrical configuration and operational parameters (feedstock's initial particle size, feeding rates, and solar power input) for maximum reaction extent and solar-to-chemical energy conversion efficiency of a 5 kW prototype reactor and its scale-up to 300 kW. For the 300 kW reactor, complete reaction extent is predicted for an initial feedstock particle size up to 35 μm at residence times of less than 10 s and peak temperatures of 1818 K, yielding high-quality syngas with a calorific content that has been solar-upgraded by 19% over that of the petcoke gasified.     

汽轮机数字电液调节系统挂闸异常的技术完善

分析了200MW汽轮机数字电液调节系统在运行中存在的挂闸异常问题,采取了相应的技术处理措施,且运行实践效果良好。     

新型高压共轨ECU升压模块的数字化开发与优化

为了提高喷油器电磁阀的响应速率,提出了一种基于CPLD(复杂可编程逻辑器件)应用于高压共轨ECU的数字升压模块。鉴于该升压电路结构参数多,其升压电压的恢复响应要求高等特征,基于Pspice建立了升压电路的仿真模型,研究了不同电路参数下升压模块的输出特性,全面优化了该升压模块的性能。结果显示,该升压模块的最大转换效率可以达90%以上。在柴油发动机上对ECU的试验表明,升压电压最大波动不超过10%,其恢复时间仅为1.3ms,功率管最大温升仅为41℃,满足整机运行范围内ECU的需求。     

Trace metal chemistry and silicification of microorganisms in geothermal sinter, Taupo Volcanic Zone, New Zealand

As part of a pilot study investigating the role of microorganisms in the immobilisation of As, Sb, B, Tl and Hg, the inorganic geochemistry of seven different active sinter deposits and their contact fluids were characterised. A comprehensive series of sequential extractions for a suite of trace elements was carried out on siliceous sinter and a mixed silica-carbonate sinter. The extractions showed whether metals were loosely exchangeable or bound to carbonate, oxide, organic or crystalline fractions. Hyperthermophilic microbial communities associated with sinters deposited from high temperature (92–94°C) fluids at a variety of geothermal sources were investigated using SEM. The rapidity and style of silicification of the hyperthermophiles can be correlated with the dissolved silica content of the fluid. Although high concentrations of Hg and Tl were found associated with the organic fraction of the sinters, there was no evidence to suggest that any of the heavy metals were associated preferentially with the hyperthermophiles at the high temperature (92–94°C) ends of the terrestrial thermal spring ecosystems studied.     

Assessment methods of material ageing using Sdobyrev''s creep rupture model

The physical aspects of the activation energy, in higher and high temperatures, of the metal creep process were examined. The research results of creep-rupture in a uniaxial stress state and the criterion of creep-rupture in biaxial stress states, at two temperatures, are then presented. For these studies creep-rupture, taking case iron as an example the energy and pseudoenergy activation was determined. For complex stress states the criterion of creep-rupture was taken to be Sdobyrev's, i.e. σ_red = σ₁ β + (1 − β)σ_i, where: σ₁-maximal principal stress, σ_i-stress intensity, β-material constant (at variable temperature β = β(T)). The methods of assessment of the material ageing grade are given in percentages of ageing of new material in the following mechanical properties: 1) creep strength in uniaxial stress state, 2) activation energy in uniaxial stress state, 3) criterion creep strength in complex stress states, 4) activation pseudoenergy in complex stress states. The methods 1) and 3) are the relatively simplest because they result from experimental investigations only at nominal temperature of the structure work, however, for methods 2) and 4) it is necessary to perform the experimental investigations at least at two temperatures.     

Production of hydrogen from sewage biosolids in a continuously fed bioreactor: Effect of hydraulic retention time and sparging

Hydrogen was produced from primary sewage biosolids via mesophilic anaerobic fermentation in a continuously fed bioreactor. Prior to fermentation the sewage biosolids were heated to 70 °C for 1 h to inactivate methanogens and during fermentation a cellulose degrading enzyme was added to improve substrate availability. Hydraulic retention times (HRT) of 18, 24, 36 and 48 h were evaluated for the duration of hydrogen production. Without sparging a hydraulic retention time of 24 h resulted in the longest period of hydrogen production (3 days), during which a hydrogen yield of 21.9 L H₂ kg⁻¹ VS added to the bioreactor was achieved. Methods of preventing the decline of hydrogen production during continuous fermentation were evaluated. Of the techniques evaluated using nitrogen gas to sparge the bioreactor contents proved to be more effective than flushing just the headspace of the bioreactor. Sparging at 0.06 L L min⁻¹ successfully prevented a decline in hydrogen production and resulted in a yield of 27.0  L H₂ kg⁻¹ VS added, over a period of greater than 12 days or 12 HRT. The use of sparging also delayed the build up of acetic acid in the bioreactor, suggesting that it serves to inhibit homoacetogenesis and thus maintain hydrogen production.