纤维素酶解预处理辅助超声法制备竹浆纳米纤维素

为了研究绿色、高效制备纳米纤维素(cellulose nanofibrils,CNF)的方法,该研究采用纤维素酶预处理竹浆协同超声波法制备纳米纤维素,对影响纳米纤维素得率的酶用量、酶解温度、酶解时间、超声时间等因素进行考察,得到纳米纤维素的较佳制备工艺。采用透射电子显微镜(transmission electron microscopy,TEM)、傅里叶红外光谱仪(Fourier transform infrared spectroscopy,FTIR)、旋转流变仪、X射线衍射仪(X-ray diffractometer,XRD)、紫外可见分光光度计以及热重分析仪(thermogravimetric analyzer,TGA)对纳米纤维素的形态结构、流变性能、结晶度、热稳定性等进行表征。结果表明,在酶用量8%(纤维素酶/竹浆纤维质量比)、酶解温度50℃、酶解时间10 h、超声时间6 h的条件下制备的纳米纤维素得率高达62.6%。制备得到的纳米纤维素直径约为2~24 nm,长度约为50~450 nm,结晶度为73.05%。热重分析表明,纳米纤维素在700℃后仍有高达15.3%的残余率,说明纳米纤维素的制备条件温和,对结晶区的损害较小,其良好的热稳定性有望在耐热性生物质复合材料领域有较好的应用发展。     

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。     

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。     

纳米二氧化硅/纳米纤维素复合材料制备及性能分析

使用造纸方法快速成功的制备了纳米纤维素,纳米二氧化硅复合材料,对并材料的力学性能,热性能和吸湿性能进行了分析。研究结果表明:随着纳米二氧化硅的添加量逐步提高,纳米复合材料的理论密度逐渐下降,材料的拉伸性能和模量值都有大幅度的下降。材料热解的初始降解温度和热解活化能随着纳米二氧化硅质量分数的增多提升,当纳米二氧化硅质量分数为20%时,材料初始热解温度为280℃。纳米复合材料的含水率随着吸湿时间的延长而增加,且随着纳米二氧化硅添加量的增多,材料的最终含水率不断提高,当纳米二氧化硅质量分数为20%时,纳米复合材料的最终含水率约26%,纳米复合材料的表面接触角值仅为40.4°。该研究结果可为制备了纳米纤维素/纳米二氧化硅复合材料提供参考。     

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。     

红酵母发酵豆腐渣产类胡萝卜素工艺优化

豆腐渣虽含有多种营养成分,但大约50%的干物质是难以消化的纤维素及半纤维素,直接用作饲料,饲喂效果并不理想。为了提高豆腐渣的饲用价值,进行了红酵母发酵豆腐渣产类胡萝卜素工艺优化研究。首先,在单因素试验基础上进行正交试验的结果显示,优化的豆腐渣酸解产还原糖工艺参数为:盐酸浓度1.0mol/L,料液比(g/mL)1∶10,酸解温度100℃,酸解时间3.0h,该条件下还原糖得率达29.06%±0.07%。然后,选用嗜还原糖红酵母发酵富含还原糖的豆腐渣酸解产物,以产生具有抗氧化、增强机体免疫等多种生物学功能的类胡萝卜素。通过单因素试验、Plackett-Burman试验回归分析、Box-Behnken试验及响应面分析,获得优化的发酵工艺参数:发酵底物pH值6.0,装液量80 mL/(500 mL),接种龄48 h,接种量11%(种子液浓度为8.5×10~9 CFU/mL),转速60 r/min,发酵温度31℃,发酵时间128 h;该条件下类胡萝卜素产量达(2.65±0.02)mg/L,比工艺优化前产量提高了67.7%,研究结果可为利用廉价豆腐渣开发高附加值类胡萝卜素功能饲料提供参考。     

小麦秸秆纤维素均相醚化制备羧甲基纤维素工艺优化

为了利用小麦秸秆通过均相反应制备羧甲基纤维素(CMC,carboxymethyl cellulose),采用氢氧化钠和过氧化氢回流加热法制备小麦秸秆纤维素。以加入氧化锌的氢氧化钠/尿素/硫脲体系为溶剂,采用冻融循环法溶解小麦秸秆纤维素,利用正交试验获得了该溶解体系的最佳组成。在溶解了小麦秸秆纤维素的氢氧化钠/尿素/硫脲/氧化锌的体系中,以氯乙酸钠为醚化剂制备CMC,并对其进行红外光谱分析和取代度(degree of substitution,DS)测定。结果表明:在固液比为1∶20 g/mL,质量分数为10%NaOH,反应温度为85℃,回流3.5 h和固液比为1∶30 g/m L,质量分数为3%H_2O_2,反应温度为85℃,回流3 h处理小麦秸秆,纤维素提取率最高为84.61%,同时能较好的脱除半纤维素和木质素;最佳溶解体系为:质量分数为7%NaOH,11%硫脲,5%尿素,0.05%氧化锌,0℃时,最大溶解度为2.880 1 g。红外光谱试验表明小麦秸秆纤维素与微晶纤维素特征吸收峰基本一致,醚化反应生成的CMC与商品CMC的特征吸收峰基本一致。CMC的取代度受纤维素用量、温度和氯乙酸钠与纤维素葡萄糖单元(AGU,anhydroglucose unit)的摩尔比影响,随纤维素用量和氯乙酸钠与纤维素AGU的摩尔比增大而提高,随醚化温度的增加先增大(55℃)后降低。研究结果为以小麦秸秆为原料,经NaOH和H_2O_2处理获得纤维素,溶解在加入氧化锌的氢氧化钠/尿素/硫脲体系中,与氯乙酸钠经过均相醚化反应合成取代度较高的CMC提供参考。     

雪莲果水溶性粗多糖提取分离工艺优化

为了考察雪莲果中粗多糖的较优提取分离工艺,采用水提取法提取雪莲果中多糖,以提取温度、料液比、提取时间、乙醇终浓度为影响因素,在单因素试验的基础上进行四因素三水平的正交试验。正交试验以粗多糖得率为考察指标,优化粗多糖的提取分离工艺。四因素中提取温度对试验结果影响最大,其次是乙醇终浓度和料液比,最后是提取时间。雪莲果粗多糖较优提取分离工艺为提取温度90℃,乙醇终体积分数为80%,料液比1∶20g/L,提取时间2 h。在此条件下粗多糖得率为5.11%,粗多糖的总糖质量分数为46.2%。     

中性蛋白酶水解鸡骨泥制备短肽工艺优化

为了探究酶法制备鸡骨泥短肽的最佳工艺,该文研究了以中性蛋白酶酶解鸡骨泥时各因素对短肽得率和羟自由基清除率的影响,以及鸡骨泥肽清除超氧阴离子自由基和1,1-二苯基-2-三硝基苯肼自由基(2,2-diphenyl-1-picrylhydrazyl)的能力。试验探究了酶解过程中不同底物浓度、酶浓度、反应温度和反应时间对短肽得率和羟自由基清除率的影响,采用响应曲面优化得到了以短肽得率为目标的中性蛋白酶酶解鸡骨泥的最优工艺,当反应液p H值为7.2,反应温度42℃,反应时间2 h,底物质量分数5%,酶添加量200 mg/g,该条件下制备鸡骨泥肽,测得其短肽得率为56.16%,羟自由基清除率为54.12%。采用该酶解工艺制备鸡骨泥肽,测得其对超氧阴离子自由基最高清除率为56.01%,对DPPH自由基最高清除率为81.57%,说明鸡骨泥肽具有一定的抗氧化活性,研究结果为酶法制备鸡骨泥肽提供参考。     

菜籽饼粕中多糖的酸提取工艺优化

采用五因子二次正交旋转设计,研究酸浓度、料液比、提取时间、提取温度、提取次数等5个因素对酸提取菜籽饼粕中多糖的得率的影响,用SAS8.0中响应面分析程序RSREG建立并分析了5个因素对得率的函数模型。结果表明,所得回归方程达显著水平,拟合情况良好;5个因素对得率的影响大小依次为提取温度>提取次数>提取时间>酸浓度>料液比,最佳提取温度为100℃,提取次数4～5次,提取时间(每次)1.4～1.8 h,酸浓度0.10～0.14 mol/L,料液比1∶18～1∶22,菜籽饼粕多糖得率在3.1%以上。     

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.     

Electron donor and pH relationships for biologically enhanced dissolution of chlorinated solvent DNAPL in groundwater

Biologically enhanced dissolution offers a method to speed removal of chlorinated solvent dense non-aqueous-phase liquid (DNAPL) sources such as tetrachloroethene (PCE) and trichoroethene (TCE) from aquifers. Bioremediation is accomplished by adding an electron donor to the source zone where fermentation to intermediates leading to acetic acid and hydrogen results. The hydrogen and possibly acetic acid are used by dehalogenating bacteria to convert PCE and TCE to ethene and hydrochloric acid. Reductive dehalogenation is thus an acid forming process, and sufficient alkalinity must be present to maintain a near neutral pH. The bicarbonate alkalinity required to maintain pH above 6.5 is a function of the electron donor: 800 mg/L of bicarbonate alkalinity is sufficient to achieve about 1.2 mM TCE dechlorination with glucose, 1.7 mM with lactate, and a much higher 3.3 mM with formate. Laboratory studies indicate that in mixed culture, formate can be used as an electron donor for complete conversion to ethene, contrary to pure cultures studies indicating it cannot. Various strategies can be used to add electron donor to an aquifer for DNAPL dehalogenation while minimizing pH problems and excessive electron donor usage, including use of injection-extraction wells, dual recirculation wells, and nested injection-extraction wells.     

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.     

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.