乙二醇-氯化铁预处理对棉秆酶水解效率的影响

为提高棉秆的纤维素酶水解效率,该研究以乙二醇为预处理溶剂,氯化铁为催化剂对棉秆进行预处理,实现了棉秆木质素和半纤维素的有效去除,提高了酶水解效率。以木质素和半纤维素的去除率为指标,运用正交试验方法优化乙二醇-氯化铁预处理条件。结果表明,棉秆在90%乙二醇水溶液,0.1 mol/L氯化铁,固液比1∶15,160 ℃条件下处理20 min,木质素和半纤维素去除率分别为85.7%和88.9%。相较原料,预处理后棉秆酶解率提高了7.6倍,葡萄糖产率达到100%（基质浓度5%,酶载量8.3 FPU/g,水解72 h条件下）。通过结构表征发现乙二醇-氯化铁预处理使棉秆的比表面积增大,致密结构被破坏,有效提高了棉秆的纤维素酶可及性。     

液氨和过氧化氢预处理对稻草酶解效果的影响机制

稻草是一种重要的木质纤维素资源,可以作为纤维素乙醇转化的原料。该试验通过高温过氧化氢(高温HP)、低温过氧化氢(低温HP)和液氨预处理(liquid ammonia treatment,LAT)3种预处理方式来克服生物质原料的酶解顽抗性,促进稻草酶解转化为可发酵单糖。对预处理后的稻草进行酶解试验,利用高效液相色谱法(highperformanceliquid chromatography,HPLC)定量测定了酶解液中的单糖含量,通过酶解转化率和单糖产量对预处理效果进行了分析比较。试验结果表明高温HP、低温HP和LAT 3种预处理方式均有效提升酶解率,其中LAT预处理的酶解促进作用效果最佳,高温HP预处理次之。稻草在120℃、预处理时间为60 min、30%H2O2水溶液与原料质量比为0.75∶1的高温HP预处理下,在纤维素酶添加量为15U/g时葡聚糖和木聚糖的酶解率分别为61.55%和47.82%,每千克干基稻草原料经144h酶解可生产单糖334.5 g。稻草在90℃、含水率60%、驻留时间为5 min、液氨与原料比例为1∶1的LAT预处理下,在纤维素酶添加量为15 U/g时,葡聚糖和木聚糖的72 h酶解率分别为88.62%和79.29%,每千克干基稻草原料经144 h酶解可生产单糖554.1 g,是未处理原料的2.9倍,总糖回收率达到90%。综上所述,LAT预处理稻草的酶解率显著高于其他单一预处理方法,该研究结果可为稻草制取燃料乙醇提供基础数据。     

玉米芯碱液预处理条件优化

该文对木质纤维素原料玉米芯碱液预处理条件进行了优化,以去除木质素,提高半纤维素、纤维素的酶解得率为目的。采用单因素多水平和正交试验方法得到最优预处理条件为：预处理时间12 h,温度70℃,液固比23︰1,反应液中各物质质量分数为氨水2.5%、过氧化氢 0.6%、硅酸钠5%、硫酸镁0.05%。在此最优条件下,玉米芯残渣得率为59.74%、半纤维素保留率为56.60%、纤维素的保留率为86.20%、木质素的保留率为11.83%。残渣经分步酶解（木聚糖酶和纤维素酶）,半纤维素、纤维素、总的酶解得率分别为41.36%、88.09%、69.21%,比未经预处理的玉米芯酶解得率分别提高了39.18%、40.89%、44.88%。结果表明,酶解得率与半纤维素的损失、木质素的去除有直接相关性。     

乙醇-磷酸预处理对稻草酶解糖化的影响

为了提高制生物质酒精时稻草酶解糖化率,该文采用常温常压乙醇-磷酸预处理稻草。研究了预处理温度、乙醇体积分数、预处理时间对稻草糖化率的影响以及最优条件下的回用乙醇-磷酸预处理稻草糖化效果。结果表明,在50℃、乙醇体积分数50%、处理时间60?min条件下,稻草酶解糖化率从10.03%提高到57.75%。回用乙醇-磷酸预处理后稻草糖化率达到56.89%,与乙醇-磷酸预处理后糖化率相接紧,可减少蒸馏回收乙醇次数,降低能量消耗,节省运行费用。对比预处理前后稻草物理和化学性质的变化表明,乙醇-磷酸预处理使稻草的晶状结构遭到破坏、孔隙度增加、比表面增大,易于被微生物或酶酶解。乙醇-磷酸预处理后的过滤液容易通过蒸馏、离心、过滤等方式分离得出乙醇、木质素、磷酸等有用原料。该研究提供了一种温和条件下可运用于循环生产的稻草预处理方法。     

糠醛渣的纤维素酶水解及其最优纤维素转化条件

该文对糠醛渣的纤维素酶水解特性进行了研究,探索利用玉米芯制糠醛联产燃料乙醇工业化生产的可行性。分析糠醛渣组分,表明其半纤维素质量分数为3.1%,纤维素为31.6%,说明糠醛生产过程对玉米芯的预处理基本满足高效酶解糖化糠醛渣并转化乙醇的要求;通过纤维素酶用量、温度、pH值、固液比、转速等因素进行条件优化,确定最佳水解条件：每克底物酶用量为6.7FPU,固液质量体积比1︰6,pH5.2,转速80 r/min;在糠醛渣水解体系中加入吐温80,结果表明在酶施用量较低情况下（6.7 FPU/g）,吐温80对提高糠醛渣水解转化率效果更为明显;通过最优化水解条件,使糠醛渣纤维素转化率达到78%,据此初步判定以糠醛渣为原料转化乙醇的工业化生产具有较大潜力。     

稻草秸秆的碱性臭氧预处理效果

为了研究碱性臭氧预处理对稻草秸秆酶水解、表观结构及成分的影响,将稻草秸秆碱性臭氧预处理后进行酶水解,对处理前后的稻草秸秆进行了扫描电镜观察及成分分析,并对处理后溶液进行了紫外光谱分析。结果表明：碱性臭氧预处理能将稻草秸秆中的木质素氧化降解为小分子的有机酸,降低了稻草秸秆中木质素的含量,提高了纤维素的含量。扫描电镜观察显示经碱性臭氧预处理过的稻草秸秆,机械组织暴露,孔隙度大,酶解的有效比表面积大。在pH值5.0、每单位底物加酶量31.2 mg/g、45℃条件下,碱性臭氧预处理稻草秸秆酶水解120 h时还原糖达到了902 mg/g,糖化率为92.57%。在相同酶解条件下,碱性预处理与未处理稻草秸秆的糖化率分别为74.90%与53.53%。碱性臭氧预处理稻草秸秆的糖化率明显高于碱性预处理与未处理稻草秸秆的糖化率。     

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。     

核桃青皮中多元酚类化合物的提取及含量分析

核桃在采摘及加工过程中产生的青皮遗弃物处理已经成为一个社会问题。以核桃青皮为原料,经酶解、微波超声波辅助处理后获得多元酚类化合物提取液,检测化合物中没食子酸、原花青素和儿茶素的含量。结果显示,固料比1∶4,1%复合提取酶、温度为50℃、p H6.0下恒温振荡12 h;微波超声波萃取仪处理15 min,分3阶段,每阶段5 min。(丙酮为萃取剂,液液比1∶6,设置温度分别为50℃、60℃、70℃;超声波功率分别为800 W、900 W、1 000 W;微波功率分别为100MHz、200 MHz、300 MHz;超声波频率恒定为25 k Hz,转速1 000 r/min);加4%明胶产生沉淀后分别氯仿、乙酸乙酯萃取获得鞣质提取液提;分别检测到没食子酸的含量为1.125 mg/g,原花青素的含量为1.71 mg/g,儿茶素的含量为0.035 mg/g。     

核桃青皮中多元酚类化合物的提取及含量分析

核桃在采摘及加工过程中产生的青皮遗弃物处理已经成为一个社会问题。以核桃青皮为原料,经酶解、微波超声波辅助处理后获得多元酚类化合物提取液,检测化合物中没食子酸、原花青素和儿茶素的含量。结果显示,固料比1∶4,1%复合提取酶、温度为50℃、p H6.0下恒温振荡12 h;微波超声波萃取仪处理15 min,分3阶段,每阶段5 min。(丙酮为萃取剂,液液比1∶6,设置温度分别为50℃、60℃、70℃;超声波功率分别为800 W、900 W、1 000 W;微波功率分别为100MHz、200 MHz、300 MHz;超声波频率恒定为25 k Hz,转速1 000 r/min);加4%明胶产生沉淀后分别氯仿、乙酸乙酯萃取获得鞣质提取液提;分别检测到没食子酸的含量为1.125 mg/g,原花青素的含量为1.71 mg/g,儿茶素的含量为0.035 mg/g。     

文冠果壳基活性炭制备工艺优化与性能表征

文冠果壳为文冠果榨油后的废弃物,为避免环境污染,充分利用这种废弃物制成高附加值的活性炭,该研究以文冠果壳为原料,采用磷酸活化法制备活性炭,以固液比、磷酸浓度、活化时间和活化温度为自变量,活性炭的碘吸附值为因变量,经响应面试验优化制备工艺,探究文冠果壳活性炭的吸附性能。结果表明,通过响应面试验优化得到最佳工艺条件：固液比1∶1 g/mL,磷酸浓度71%,活化时间158 min,活化温度540℃,此时碘吸附值为(1 127.377±2.406) mg/g,与预测的碘吸附值误差仅为0.390%。与文冠果壳相比,经活化得到的活性炭水分和灰分明显降低,C元素质量分数升高至69.702%;活性炭的比表面积为841.438 m²/g,总孔容为0.593 cm³/g,平均孔径为4.361 nm,孔隙结构发达,主要以介孔为主,且官能团主要为羰基。因此可以用文冠果壳制备出吸附性能好的活性炭,该结果可为磷酸活化法制备文冠果壳基活性炭的工业化生产提供一定参考。     

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。     

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.     

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,     

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.     

Variation in quality parameters between and within 14 Nordic tree fruit and berry species

Abstract

A 3-year study was carried out to investigate quality parameters in 14 tree fruit and berry species grown in southern Norway. The species were blueberry, apple, aronia, sour cherry, sweet cherry, red raspberry, strawberry, blackcurrant, gooseberry, red currant and elderberry, harvested along with wild bilberry, cloudberry and lingonberry. Significant differences between species were identified for all quality parameters. The coefficient of variation between species was lowest for pH (12.5%), dry matter (18.9%) and soluble solids (25.3%), followed by titratable acids (59.3%), total phenolics (83.8%), antioxidant capacity FRAP (85.7%) and antiradical power by the DPPH-assay (97.8%), total monomeric anthocyanins (132%) and ascorbic acid (137%). Average coefficient of variation within species were lower and ranged from 4 (pH) to 62% (ascorbic acid). Only the FRAP values were significantly affected by harvesting year with lower levels in 2004 than in 2005 and 2006. There were significant interactions between species and harvesting year for dry matter, soluble solids, pH, ascorbic acid and FRAP. The results indicate generic ranges in composition within species independent upon growing location and climate, and the composition of the tree fruits and berries is not likely to deviate from these ranges. It is concluded that desirable composition of tree fruits and berries and their products should primarily be achieved by selection among species rather than searching fors broadened variation within individual species.     

Potassium Fixation and Release Characteristics in Rhizosphere and Nonrhizosphere Soils for a Rapeseed–Rice Cropping Sequence

Potassium (K) fixation and release in soil are important factors in the long-term sustainability of a cropping system. Changes in K concentration and characteristics of K fixation and release in rhizosphere and nonrhizosphere soils in the rapeseed (Brassica napus L.)–rice (Oryza sativa L.) rotation were investigated using a rhizobox system. The concentrations of different forms of K in both rhizosphere and nonrhizosphere soils decreased with plants compared to without plants, regardless of K fertilizer application. Potassium uptake by crops mainly came from the rhizosphere soil. In the treatment without K fertilizer (–K), the main form of K supplied by the soil to the crops was 1.0 mol L^?1 nitric acid (HNO₃) nonextractable K, followed by nonexchangeable K, and then exchangeable K. In the treatment with K fertilizer (+K), the main K forms supplied by the soil to the crops were exchangeable K and nonexchangeable K. The amount and rate of K fixation after one cycle of the rapeseed–rice rotation was greater in rhizosphere soil than in nonrhizosphere soil. The amount and rate of K fixation of soil in the +K treatment were significantly less than in the –K treatment. The cumulative amounts of K released with 1.0 mol L^?1 ammonium acetate (NH₄OAc) and 1.0 mol L^?1 HNO₃ extraction increased with the increasing numbers of extractions, but the K-releasing power of soil by successive extraction decreased gradually and finally became almost constant. The release of K was less in rhizosphere soil than in nonrhizosphere soil. The release of K in the +K treatment was similar to that in the –K treatment in rhizosphere soil, but the K release in nonrhizosphere soil was greater with the +K than the –K treatment. Overall, the information obtained in this study will be helpful in formulating more precise K fertilizer recommendations for certain soils.     

Increase in auxiliary photoprotective photosynthetic pigments in wheat seedlings induced by Azospirillum brasilense

Inoculation of wheat seedlings with the plant growth-promoting bacterium Azospirillum brasilense Cd was immobilized in alginate microbeads and, without applying any stress, significantly increased the quantity of several photosynthetic pigments, such as chlorophyll a, chlorophyll b, and the auxiliary photoprotective pigments violaxanthin, zeaxanthin, antheroxanthin, lutein, neoxanthin, and β-carotene. This resulted in greener plants with no apparent visible stress. After monitoring the quantity of photosynthetic pigments for 4 weeks, we observed that inoculated plants had higher quantities of pigments in shoot and stem. The greatest difference in the quantity of all pigments between inoculated and noninoculated plants occurred in the first week of growth. Regardless of treatment, the quantity of pigments in stems was three to four times less than the quantity of these pigments in shoots. Application of Azospirillum, either as liquid inoculant or as alginate microbeads, did not alter the positive effect of the bacteria on pigment production or the positive response of the plants towards A. brasilense Cd inoculation.     

In-situ enrichment and analysis of atrazine-degrading microbial communities using atrazine-containing porous beads

We examined the community composition of microbes that colonized atrazine-containing beads buried in agricultural soils that differed in atrazine treatment history. Bacterial abundance was 5-40-fold greater in atrazine-fortified beads. In beads containing 20 mg atrazine kg⁻¹ buried in soil with a history of atrazine application (conditioned soil), the abundance of Actinobacteria increased approximately 80-fold whereas in control soil, Actinobacteria were enriched only 10-fold and the gamma-Proteobacteria and Planctomycetes increased by 60- and 25-fold, respectively. The gamma-Proteobacteria were enriched by 120- and 230-fold in beads containing 200 mg atrazine kg⁻¹ in conditioned and control soil, respectively. The results demonstrate that BioSep^® beads are a suitable matrix for recruiting a diverse subset of the bacterial community involved in atrazine degradation.     

Genetic similarities among Spanisch populations of Agropyron, Elymus and Thinopyrum, using PCR-based markers

Arbitrary oligonucleotides were used as primers to amplifygenomic DNA of 48 wild Spanish populations of Agropyroncristatum, Elymus hispanicus,E. caninus,E. repens,Thinopyrum curvifolium, Th.junceum and Th.intermedium. Genetic diversity was analysedusing nineteen primers. The number of amplified products ranged from8 to 18 per primer and a total of 240 markers were scored. Differentlevels of intraspecific genetic diversity were found, the allogamousspecies E. repens andTh. intermedium being themost variable. Jaccard's similarity coefficients for internalmeasure within and between populations were used to produce a clusterdiagram. The results demonstrate differences in the degree ofsimilarity between taxonomic units. Interpopulational variability andinterspecific genomic relationships of these species arediscussed.     

Mycorrhizae,biocides, and biocontrol. 4. Response of a mixed culture of arbuscular mycorrhizal fungi and host plant to three fungicides

The effects of three commonly used fungicides on the colonization and sporulation by a mixture of three arbuscular mycorrhizal (AM) fungi consisting of Glomus etunicatum (Becker & Gerd.), Glomus mosseae (Nicol. & Gerd.) Gerd. & Trappe, and Gigaspora rosea (Nicol. & Schenck) in symbiosis with pea plants and the resulting response of the host-plant were examined. Benomyl, PCNB, and captan were applied as soil drenches at a rate of 20 mg active ingredient kg^-1 soil 2 weeks after transplanting pea seedlings in a silty clay-loam soil containing the mixed inocula of AM fungi (AM plants). Effects of fungicides were compared to untreated plants that were inoculated with fungi (AM control). The effect of mycorrhizal inoculation on plant growth was also examined by including nonmycorrhizal, non-fungicide-treated plants (non-AM control). Fungicides or inoculation with AM fungi had only a small effect on the final shoot weights of pea plants, but had greater effects on root length and seed yield. AM control plants had higher seed yields and lower root lengths than the corresponding non-AM plants, and the fungicide-treated AM plants had intermediate yields and root lengths. Seed N and P contents were likewise highest in AM control plants, lowest in non-AM plants, and intermediate in fungicide-treated AM plants. All three fungicides depressed the proportion (%) of root length colonized by AM fungi, but these differences did not translate to reductions in the total root length that was colonized, since roots were longer in the fungicide-treated AM plants. Pea plants apparently compensated for the reduction in AM-fungal metabolism due to fungicides by increasing root growth. Fungicides affected the population of the three fungi as determined by sporulation at the final harvest. Captan significantly reduced the number, relative abundance, and relative volume of G. rosea spores in the final population relative to the controls. The relative volume of G. etunicatum spores was greater in all the fungicide-treated soils, while G. mosseae relative volumes were only greater in the captan-treated soil. These findings show that fungicides can alter the species composition of an AM-fungal community. The results also show that AM fungi can increase seed yield without enhancing the vegetative shoot growth of host plants.