螺杆挤压连续汽爆玉米秸秆的稀酸水解效果

对采用螺杆挤压连续汽爆方法处理的玉米秸秆进行酸水解,探讨稀硫酸和稀盐酸在酸浓度、反应时间、反应温度及固液比等因素对经过处理的玉米秸秆水解效果的影响。结果表明：在硫酸水解正交试验中,影响水解过程的因素由主到次分别为：原料类型、固液比、水解温度、酸浓度和水解时间。其优化条件为：硫酸浓度3%,水解温度110℃,水解时间60 min,固液比1︰15,此时120℃下汽爆10 min的原料的水解效果最好,还原糖得率可达39.7%。在盐酸水解的正交试验中,影响水解过程的因素由主到次分别为：水解温度、原料类型、水解时间、酸浓度和固液比。在最优条件下,即采用120℃下汽爆6 min的原料,在盐酸浓度为3%,水解温度 110℃,水解时间60 min,固液比1︰20的条件下进行水解,还原糖得率为42.0%。结果表明,螺杆挤压连续汽爆方法能有效提高玉米秸秆在稀酸条件下的水解能力。     

脂肪酶催化制备生物基化学品乙酰丙酸乙酯的工艺优化

为了建立新型生物基化学品乙酰丙酸乙酯的生物法合成工艺路线,该文以乙酰丙酸为主要原料,采用脂肪酶生物催化转化法制备乙酰丙酸乙酯。考察了溶剂量、酶量、反应时间、原料醇酸摩尔比对乙酰丙酸乙酯产率的影响,并在此基础上,采用响应面试验设计优化了乙酰丙酸乙酯生成工艺条件。结果显示:在反应温度为45℃、转速为150 r/min、反应时间为2.8 h、催化剂量为35.5 mg、溶剂量为2.6 mL、醇酸摩尔比为1.7:1时,乙酰丙酸乙酯的摩尔产率达到87.6%。进一步考察在最优条件下催化剂的循环利用寿命,酶在重复12次的情况下产率依然能够达到76.3%。研究结果为酶催化乙酰丙酸乙酯提供了依据。     

挤压豆渣中可溶性膳食纤维制备工艺的优化

为了获得碱法制备挤压豆渣中可溶性膳食纤维的最适工艺参数,以液固比、温度、时间和碱浓度为试验因子,以可溶性膳食纤维产率为响应值,采用中心旋转组合试验设计进行试验。结果表明：4个因素对可溶性膳食纤维产率的影响大小依次为碱浓度＞液固比＞温度＞时间。通过典型性分析得出可溶性膳食纤维最适制备条件为：液固比26∶1、温度89℃、时间68 min、碱浓度1.12%。在此条件下,可溶性膳食纤维产率的预测值为33.96%,验证试验所得可溶性膳食纤维产率为34.12%。回归方程的预测值和试验值差异不显著,所得回归模型拟合情况良好,达到设计要求。在本试验优化的条件下,以经挤压豆渣为原料制备的可溶性膳食纤维产率（34.12%）显著高于以未经挤压豆渣为原料的产率（13.51%）。     

常压温和条件下丙酸预处理小麦秸秆的工艺优化

为了提高小麦秸秆木质纤维素的能源化利用效率,该文研究了常压温和条件下丙酸预处理小麦秸秆的工艺优化。该方法的最佳工艺条件为：料液比1∶16、粒度40目、丙酸质量浓度900 g/L、催化剂质量浓度3 g/L、温度70℃,处理时间150 min。在此条件下,小麦秸秆的纤维素保留率为92.6%,半纤维素和木质素的脱除率分别为98.3%和70.5%。丙酸预处理后小麦秸秆的酶解得率90.3%。研究表明,在常压温和条件下,丙酸法预处理小麦秸秆,可有效地将其分离为纤维素、半纤维素、木质素3大组分。     

超低酸预处理结合酶解提高玉米秸秆糖化效率

为提高纤维素酶解糖化的效率,该文采用超低浓度硫酸水解预处理废弃玉米秸秆。重点考察了不同酸浓度、反应温度、反应时间条件下超低浓度酸水解及后续酶解的总还原糖、葡萄糖及木糖的产率,详细叙述了总还原糖及各种单糖在酸水解及酶解过程中的转化规律,通过正交试验确定酸水解的最佳工况为酸浓度0.1%,反应温度160℃,反应时间55 min,搅拌180 r/min,固液比1∶10。酸水解后进行酶解(酶用量5%,pH值4.6,时间24 h,温度50℃)得到还原糖、葡萄糖、木糖产率分别为56.22%、16.97%、18.83%。通过红外光谱和纤维素分析仪对酸水解和酶解后的残渣进行分析可知,纤维素、半纤维素的转化率分别为88.52%、95.18%,进一步计算还原糖、葡萄糖、木糖的转化率为88.11%、44.86%、72.49%。该方法较大程度避免了还原糖在酸水解过程中的降解,保证了半纤维素还原糖的转化效率,进一步提高了总还原糖的产率,为超低酸水解在燃料乙醇领域提供了新的应用途径。     

用于复合材料的小麦秸秆纤维性能及制备工艺

针对目前中国小麦秸秆利用率不高以及燃烧秸秆所带来的环境污染问题,该文研究了利用稀烧碱溶液处理小秸秆以制备用于复合材料的小麦秸秆纤维的性能及制备工艺,研究了氢氧化钠溶液质量分数、液固比、处理温度和处时间等工艺参数与小麦秸秆纤维失重率的关系,并对所制备的小麦秸秆纤维的强伸性能、表面性能进行了测试。结果明,小麦秸秆经稀烧碱溶液处理(氢氧化钠质量分数4%、液固比30mL/g、处理温度100℃、处理时间60min)后制的小麦秸秆纤维力学性能与原样相比没有明显损伤,但内、外表面结构均变得疏松,比表面积增大,滴水接触角变小从而提高了聚合物聚乳酸对秸秆纤维的浸润性能,提高了二者之间界面的粘结性。该研究结果为利用小麦秸秆制备秸纤维增强聚乳酸复合材料提供参考。     

纤维乙醇工艺中酸处理稻秸秆反应条件的优化

以木糖含量为指标,在稀酸处理条件中时间、浓度和液固比影响试验结果的基础上,采用二次回归正交设计优化稀酸处理的条件,建立稀酸处理3因素与木糖含量之间的回归方程关系式,通过验证得到方差分析具有显著性。同时得到各因素的主次因素顺序：时间（x1）＞液固比（x2）＞浓度（x3）。并通过回归方程求解得到的稀酸处理秸秆条的最佳工艺参数为：反应时间2 h,稀酸体积分数4.1%、液固比22︰1,此条件下可以求得较为稳定的木糖质量浓度为0.332 g/L。研究中通过采用二次回归正交设计方法,较大程度地减少了试验次数和优化工艺条件,从而为试验研究提供了一定的依据。此外,该试验研究结果表明3因素交互项对试验结果影响不显著,但反应时间和稀酸浓度2因素的水平选择上有待调整。     

蒸汽爆破过程麦秆木质纤维素的转化

采用低压蒸汽爆破技术处理小麦秸秆木质素。通过单因素试验,考察蒸汽爆破过程汽爆压力、液固比、物料粒度、维压时间对木质纤维素降解的影响,木质素的降解率达到22.67%。设计L9(34)正交试验,上述因素影响主次顺序为汽爆压力>液固比>维压时间>物料粒度,优化条件为汽爆压力0.6 MPa,液固比为20︰1,维压时间为30 min,物料粒度为20～60目,且对优化结果进一步验证。红外光谱分析表明,经汽爆后麦秆木质素结构受到了一定程度的破坏;扫描电镜观察,麦秆的纤维束受到了破坏,发生了断裂,且出现了多孔的结构。     

不同预处理和发酵条件对浒苔沼气产率的影响

为了有效利用绿潮海藻资源,该文开展了浒苔厌氧发酵产沼气潜力及其特性的试验研究。探讨了浒苔不同预处理、发酵温度和料液浓度对产气量和所产沼气的甲烷体积分数的影响。结果表明,粉碎粒度对浒苔厌氧发酵沼气产率有一定影响,相同条件(发酵温度为35℃和料液总固体(TS)质量分数为3%)下,粗粒(1.50mm)比细粒(0.15mm)的单位质量挥发性固体(VS)产气率高,分别为327.1和458.5mL/g;发酵温度对浒苔厌氧发酵产沼气产率的影响是,随着温度的提高沼气产率先增加而后降低,当粉碎粒度为1.5mm的浒苔在发酵料液TS质量分数为3%条件下,分别在25℃、35℃和55℃温度下发酵时,35℃的料液单位质量VS产气率比25℃和45℃分别高31.3%和7.5%;随着料液TS质量分数的提高,沼气产率先增加而后降低,利用粒度为1.50mm的浒苔制备TS质量分数分别为3%、6%和10%的料液在35℃温度发酵时,TS质量分数为6%的料液产气率最高,达到465.2mL/g,所产沼气的甲烷体积分数比3%的料液高5.3%,且与10%的料液相当。因此在浒苔粉碎粒度为1.50mm,料液TS质量分数为6%以及温度为35℃的发酵条件下,对提高浒苔产气量、甲烷体积分数和发酵系统稳定性比较有利。该研究可为浒苔厌氧发酵产沼气技术和设备研发以及其他大型海藻产沼气技术的研究提供参考。     

微波强化酸预处理玉米秸秆乙醇化工艺研究

采用酸预处理正交试验和微波强化酸预处理试验，研究时间、温度、基质浓度、硫酸浓度及粒径对玉米秸秆糖化预处理效果的影响。结果表明：酸预处理时，时间、温度、硫酸浓度、基质浓度、粒径5个因素都是主要影响因子，其最佳条件为：时间2 h、温度130℃、硫酸浓度3%、基质浓度35 g/L、粒径0.50 mm；微波可强化酸预处理效果，提高糖化速度，秸秆还原糖得率与酸预处理的得率基本持平，微波强化酸预处理的最优条件为:粒径0.50 mm、基质浓度35 g/L，硫酸浓度4%，在255 W微波作用下预处理60 min。     

低氮和干旱胁迫对富士和秦冠生长及氮素利用的影响

【目的】以富士（Fuji）、 秦冠（Qinguan）嫁接在平邑甜茶（Malus hupehensis Rehd.）上的当年生盆栽苗为试验材料,采用砂培方法,研究了缺氮胁迫和干旱对富士和秦冠生长情况、 光合参数、 植株各部位氮磷钾含量及氮素利用效率的影响,分析比较了低氮干旱条件下富士和秦冠生长及氮素利用的差异,以期为果树生产高效肥水利用提供理论指导。【方法】试验共设四个处理: 正常氮正常水（ZZ）、 低氮正常水（DZ）、 正常氮干旱（ZG）、 低氮干旱（DG）。氮素和水分均设置两个水平,分别为正常氮（6 mmol/L NO-3-N）、 低氮（0.3 mmol/LNO-3-N）、 正常供水（保持盆中砂子相对含水量为饱和含水量的80%~85%）、 干旱处理（保持盆中砂子相对含水量为饱和含水量的60%~65%）。【结果】富士和秦冠的生物量（茎和叶）、 株高茎粗等生长指标以及光合速率、 气孔导度、 蒸腾速率均为正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）,并且相对应处理下秦冠的以上指标均高于富士;正常供水下,缺氮处理使富士、 秦冠的根冠比比正常氮处理均有所增加,富士提高了2.05%,秦冠提高了22.40%。富士和秦冠的氮、 磷、 钾含量均表现出正常氮正常水（ZZ）＞低氮正常水（DZ）＞正常氮干旱（ZG）＞低氮干旱（DG）; 氮、 钾元素含量在植株各部位的分布顺序依次是叶＞根＞茎,磷元素则是根＞叶＞茎;光合氮素利用效率（PNUE）和氮素利用效率表现为秦冠处理之间差异极显著,富士处理之间差异不显著;秦冠的PNUE和NUE明显高于富士,在低氮正常水（DZ）处理下,秦冠氮肥利用率比富士高42.07%,在低氮干旱（DG）处理下高64.14%;低氮胁迫下富士和秦冠的NUE显著提高,并且秦冠提高的幅度高于富士。【结论】施用氮肥能够显著提高富士与秦冠的干物质量,同等水肥条件下,秦冠生长优于富士;水分亏缺会减少叶片对氮的吸收,干旱条件下适度增施氮肥,可提高果树的抗旱能力;低氮干旱胁迫下秦冠的生长指标、 光合指标及氮素利用效率指标均优于富士,表现出较强的抗低氮干旱胁迫的能力。     

Biodiversity and ecogeography of wild Lactuca spp. in some European countries

Staff members of the Department of Botany of Palacký University in Olomouc and Gene Bank Department – Workplace Olomouc, Research Institute of Crop Production in Prague, Czech Republic, conducted an expedition in seven European countries (Austria, Czech Republic, France, Germany, Italy, the Netherlands, Switzerland) in August/September 1999 to collect wild Lactuca spp. germplasm and study its geographic distribution, ecology and biodiversity. During the mission, more than 600 locations were visited resulting in the collection of 602 seed samples (accessions) of wild Lactuca species and 13 seed samples of related genera (Chondrilla and Mycelis). Lactuca serriola f. serriola, L. serriola f. integrifolia, L. saligna and L. viminea subsp. chondrilliflora were prevalent in southern Europe (Italy, France), however, only L. serriola was common in central and western Europe (Austria, Czech Republic, Germany, Netherlands, Switzerland). The greatest diversity of Lactuca species was found in France, where also the most seed samples (165) were collected. The most characteristic habitats with a high density of Lactuca spp. populations were observed along roads and highways, grassy ditches, ruderal communities, and dust-heaps. Natural infections by powdery mildew (Erysiphe cichoracearum) and downy mildew (Bremia lactucae) on some wild Lactuca spp. were observed. Recent observations concerning the geographic distribution, population structure, habitats, and natural occurrence of diseases of Lactuca spp. are discussed. This assemblage of genetic resources of Lactuca spp. can serve as the basis of future studies of species diversification, spatial population structure, plant microevolution, domestication processes, and genetic variability of host-parasite interactions.     

Pasture Vegetation Elemental Analysis by Laser-Induced Breakdown Spectroscopy

Laser-induced breakdown spectroscopy (LIBS) is a new technique for the analysis of plant material. This study investigates the application of LIBS to pasture-based plant samples. The LIBS measurements were obtained from pelletized pasture samples (100 samples) that had been also analyzed by inductively coupled plasma–optical emission spectroscopy (ICP-OES) following microwave digestion for calibration and comparison purposes. Comparisons for elements sodium (Na), potassium (K), magnesium (Mg), calcium (Ca), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), boron (B), phosphorus (P), and sulfur (S) showed that LIBS could be used for almost all the standard profile total elements with concentrations down to low mg/kg levels (observed error of Na: 0.024 percent, K: 0.18 percent, Mg: 0.016 percent, Ca: 0.073 percent, P: 0.017 percent, Mn: 31 mg/kg, Fe: 150 mg/kg, Zn: 6.6 mg/kg, and B: 1.1 mg/kg). Elemental analysis at less than mg/kg levels was not possible using LIBS. The elements S and Cu were particularly difficult to analyze with reliability using LIBS at the concentration levels found in the plant samples. Replacing microwave digestion and subsequent ICP analysis with a direct analysis of dried plant samples using LIBS has the potential to improve the productivity and reduce the cost of testing.     

Properties of anaerobically digested and composted municipal solid waste assessed by linking soil mesofauna dynamics and nitrogen modelling

We have studied the effect of anaerobically digested (ADMSW) and composted municipal solid waste (CMSW) on mineralization and foodweb dynamics to verify the hypothesis that ADMSW would immobilize N right after addition to soil in contrast to addition with CMSW. Another hypothesis was that the mesofauna (enchytraeids and microarthropods) would stimulate N release from the decomposer community. We measured excretion of -N and urea-N from the mesofauna and hypothesized that enchytraeids would release urea. ADMSW and CMSW were amended to pots with sandy loam and barley. The pots were divided into treatments with or without mesofauna. Mesofauna, plant N and biomass, soil N and ergosterol (fungal biomass) were measured over a 113-day period of four equidistant samplings. Soil respiration, N mineralization and N release by the mesofauna were modelled from concurrent studies. ADMSW- and CMSW-treated soils initially (<20 days) immobilized N. The amendments did not increase plant growth substantially, and this was probably due to N-limitation in the early stages of plant growth. Enchytraeid abundance was about three times higher in ADMSW- than CMSW-treated soils, indicating that ADMSW contained more labile compounds, bacteria, and microfauna. The mesofauna did not affect N-content, but the cumulated -N excreted by the mesofauna was estimated to be substantial and about one-fifth of total plant N in ADMSW. An explanation for this discrepancy might be that in the absence of the mesofauna, other members of the detrivore and microbivore community performed the mesofauna’s function. Neither enchytraeids nor microarthropods excreted urea.     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions: Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Faculty positions:Center for Agricultural Resources Research,Chinese Academy of Sciences

正The Center for Agricultural Resources Research(CARR),the Institute of Genetics and Developmental Biology(IGDB),Chinese Academy of Sciences,invites applicants for several research group leader positions.CARR is one of the research organizations in Chinese Academy of Sciences(CAS).We seek nominations and applications from individuals who have expertise and a record of accomplishment in research areas related to ecology,agro-hydrology,     

Assessing the effectiveness of conservation measures: Resolving the “wicked” problem of the Steller sea lion

“Wicked” problems are those that are complex and that change when solutions are applied. Many conflicts in conservation fall into this category. The study approached the problem of how to constrain the apparent wickedness of a problem in the conservation management of a species by using simple empirical indicators to carry out iterative assessment of the risk to a population and to document how this risk evolves in relation to the addition of new data and the implementation of management actions. Effects of high levels of uncertainty within data and also concerning population structure were examined through stochastic simulation and by exploration of scenarios. Historical trends in the example used, the Steller sea lion, showed rapid declines in abundance in some regions during the 1980s. The current total population is 130,000-150,000 Steller sea lions through Alaska and British Columbia and this number has been stable since about 1990 in spite of regional differences in population dynamics. Regional differences in the sequence of changes in the number of pups and non-pups, suggested that an internal re-distribution of juveniles could have happened between 1980 and 1990. Current productivity also appears close to the long-term mean. Stochastic population projection using various scenarios showed that, based upon this history, the risk of extinction for the population has declined and is below reasonable thresholds for considering the population to be endangered. The trends in risk suggest that management actions taken since 1990 have probably been effective. Consequently, the conservation management objectives for the Steller sea lion are probably being met. The approach provides a mechanism, based upon experience and scenario analysis, for exploring future policy options and may help to constrain the debate amongst stakeholders about the cost-benefit trade-offs associated with different options.     

Soil-profile distribution of primary and secondary plant-available nutrients under conventional and no tillage

Nutrient distributions under no tillage (NT) compared with conventional disk-and-bed tillage (CT) management in the warm, humid region of the southeastern USA need to be assessed so that future placement, quantity, and type of fertilizers can be altered, if necessary, to efficiently match crop demands. We determined soil-profile distributions of pH, N, P, S, K, Ca, Mg, Na, Zn, Fe, Mn, and Cu to a depth of 0.9 m at the end of 8.5 years of continuous CT and NT management on a Weswood silty clay loam (fine, mixed, thermic Fluventic Ustochrept) in southcentral Texas. Most dramatic changes occurred within the 0–0.05 m depth, where soil under NT had lower pH, Fe, and Cu than under CT, but greater P, K, Zn, and Mn. Greater P and K under NT than under CT also occurred below the till-zone (0.15–0.3 m). At a depth of 0–0.3 m, soil under NT contained greater amounts of extractable P, K, Zn, Fe, Mn, and Cu than under CT. Nitrogen fertilization had little effect on nutrient distributions, except resulting in greater extractable K at 0–0.05 m and greater nitrate at 0–0.15 m. Few changes in soil-profile distributions were observed for extractable S, Ca, Mg, and Na. Long-term continuous use of NT on this fine-textured, high-fertility (except for N) soil had no apparent adverse effects on nutrient distributions relative to CT, but enhanced conservation and availability of P, K, Zn, Fe, Mn, and Cu near the soil surface where crop roots proliferate.     

Macroinvertebrates in North American tallgrass prairie soils: effects of fire, mowing, and fertilization on density and biomass

The responses of tallgrass prairie plant communities and ecosystem processes to fire and grazing are well characterized. However, responses of invertebrate consumer groups, and particularly soil-dwelling organisms, to these disturbances are not well known. At Konza Prairie Biological Station, we sampled soil macroinvertebrates in 1994 and 1999 as part of a long-term experiment designed to examine the effects and interactions of annual fire, mowing, and fertilization (N and P) on prairie soil communities and processes. For nearly all taxa, in both years, responses were characterized by significant treatment interactions, but some general patterns were evident. Introduced European earthworms (Aporrectodea spp. and Octolasion spp.) were most abundant in plots where fire was excluded, and the proportion of the total earthworm community consisting of introduced earthworms was greater in unburned, unmowed, and fertilized plots. Nymphs of two Cicada genera were collected (Cicadetta spp. and Tibicen spp.). Cicadetta nymphs were more abundant in burned plots, but mowing reduced their abundance. Tibicen nymphs were collected almost exclusively from unburned plots. Treatment effects on herbivorous beetle larvae (Scarabaeidae, Elateridae, and Curculionidae) were variable, but nutrient additions (N or P) usually resulted in greater densities, whereas mowing usually resulted in lower densities. Our results suggest that departures from historical disturbance regimes (i.e. frequent fire and grazing) may render soils more susceptible to increased numbers of European earthworms, and that interactions between fire, aboveground biomass removal, and vegetation responses affect the structure and composition of invertebrate communities in tallgrass prairie soils.