加压氨解预处理玉米秸秆糖化工艺研究

以玉米秸秆糖化为目的,研究加压氨解预处理对玉米秸秆还原糖产量和脱除木质素的影响,以确定其最佳工艺条件。结果表明:影响加压氨解预处理的主要因素是氨水浓度和粒径,其最优条件为氨水浓度15%,时间6min,压力0.075MPa,基质浓度150g/L,粒径1mm,可以获得1.74%的还原糖得率和43.30%的木质素去除率。     

蒸汽爆破提高小麦麸皮中水溶性戊聚糖含量及热重分析

该试验旨在研究蒸汽爆破对小麦麸皮水溶性戊聚糖含量的影响。选用市售普通小麦麸皮为原料,进行不同水料比和维压时间的蒸汽爆破处理,分别为未汽爆处理的(对照组)、处理组蒸汽压强固定为2.0 MPa,对水料比为20%、30%、50%的麸皮分别进行维压时间为30、60、120 s蒸汽爆破处理。试验结果表明,蒸汽爆破可显著提高小麦麸皮水溶性戊聚糖的含量(P0.05)。与对照组相比,在相同蒸汽压强下,蒸汽爆破处理组的水溶性戊聚糖质量分数随维压时间的延长而显著提高(P0.05),蒸汽维压处理60 s,小麦麸皮中水溶性戊聚糖的含量可提高9.0倍(P0.05)。与对照组相比,蒸汽爆破处理组的水溶性戊聚糖含量随水料比的提高而呈不同程度地提高(P0.05),水料比为30%时,小麦麸皮中水溶性戊聚糖的含量可提高9.4倍(P0.05)。综合考虑蒸汽爆破处理的提取效率与能量消耗,蒸汽爆破小麦麸皮的蒸汽压强为2.0 MPa时,适宜的水料比为30%,适宜的蒸汽爆破时间为60 s。此时,与未处理麸皮相比,小麦麸皮中水溶性戊聚糖质量分数可从1.3%提高到13.9%,提高10.8倍,中性洗涤纤维可降低17.2%(P0.05),半纤维素可降低26.7%(P0.05),半纤维素热解阶段的活化能值可提高21.5%。该研究证实蒸汽爆破技术有助于提高小麦麸皮功能性活性多糖(水溶性戊聚糖)的含量,有助于提高小麦麸皮的深加工利用。     

前处理对玉米秸秆蒸汽爆破效果的影响

为提高纤维乙醇生产过程中秸秆的预处理效果,该文研究了水预浸和CaO前处理对蒸汽爆破和酶解糖化的影响,并利用场发射扫描电镜(FE-SEM)、X-射线衍射仪(XRD)及傅里叶红外光谱仪(FTIR)对其影响机制进行了分析。结果表明:玉米秸秆经30%水(水料质量比30:100)预浸5d、经2%CaO(CaO与秸秆质量比2:100)处理3d或经30%水和2%CaO协同处理1d后再进行蒸汽爆破均可显著提高蒸汽爆破对木质素的降解,降解率由单独蒸汽爆破的20.6%分别提高到27.8%、35.1%和30.9%。玉米秸秆经3种复合预处理和酶解糖化后总糖浓度分别为3.81、3.59和3.46g/100mL,糖得率分别为42.2%、39.8%和38.3%,比单独蒸汽爆破预处理分别提高了23.7%、16.6%和12.3%。水预浸或CaO复合蒸汽爆破预处理后秸秆结构破坏严重,秸秆相对结晶度由单独蒸汽爆破的42.6%分别提高到47.0%和54.5%。水浸泡或CaO前处理可提高蒸汽爆破预处理效果和后期糖化效果,且所用试剂价格低廉,可以应用推广。     

玉米秸秆蒸汽爆破用于厌氧发酵的技术评价

蒸汽爆破可破坏木质纤维素结构,提高纤维素、半纤维素的转化利用率,是秸秆类物质利用的一种有效预处理方式。作者研究了玉米秸秆蒸汽爆破处理及其厌氧发酵过程中的能量平衡关系,结果表明相同维压时间下蒸汽爆破处理后玉米秸秆厌氧发酵过程中的能源转化率随着压力增大而增大,而在相同压力条件下均在90 s维压时间时得到最大能源转化率。玉米秸秆蒸汽爆破后在常温条件下厌氧发酵的最小和最大能源转化率分别为8.39%和11.68%,是对照组的1.38倍和1.92倍。但对蒸汽爆破玉米秸秆厌氧发酵的增量效益-费用比分析表明,因玉米秸秆蒸汽爆破处理而引起厌氧发酵产气量增加所形成产气的能量增加量小于蒸汽爆破处理所消耗的能量,从能量转换角度来说蒸汽爆破并不是玉米秸秆厌氧发酵的最经济处理方式。     

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。     

酸-超声波预处理及糖化水解稻草研究

采用室内实验方法,研究了酸-超声联合预处理稻草对其化学组成以及糖化效果的影响,并与传统酸预处理法的效果进行了对比。结果表明,与未经处理的稻草相比,经酸-超声波处理的稻草其半纤维素、木质素含量最高分别减少了64．46％、62．19％,纤维素含量最高则上升了73．20％,而酸处理的稻草相应数值只能达到56．72％、59．90％及53．41％。同时分别对两种方法的稻草糖化的工艺条件通过正交试验进行了优化,得出两种方法的稻草最佳糖化条件均为：pH值为4．8,温度为45℃,酶浓度为20mg·g-1。在该条件下,对于酸一超声波预处理稻草,在糖化108h以后还原糖浓度稳定并达到最大值26．4g·L-1,而对于酸预处理稻草,在糖化120h以后还原糖浓度才稳定并达到最大值26．2g·L-1,且前者能比后者产生更多的葡萄糖以及更少的木糖,更有利于提高后续酒精发酵的效率。     

蒸汽爆破技术在秸秆厌氧发酵中的应用

该文采用蒸汽爆破技术对秸秆进行预处理,探讨提高秸秆厌氧发酵产气量的新工艺.研究蒸汽爆破预处理的关键参数"爆破压力"和"保留时间"对秸秆厌氧发酵效果的影响.结果表明:蒸汽爆破预处理后的秸秆比未经预处理秸秆厌氧发酵的产气量提高34%～67.36%,蒸汽爆破预处理压力在3.0 MPa、保留时间为90 s时,每克干秸秆厌氧发酵沼气产量最大值达到304.72ml;蒸汽爆破预处理后,秸秆厌氧发酵的启动时间和发酵周期大大缩短.     

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。     

生物—碱氧化预处理玉米秸秆酶解条件的优化

白腐菌生物—碱氧化预处理（BAO预处理）具有环境友好、低能耗的优势,是一项很有前景的生产纤维质乙醇预处理技术。为获得预处理后玉米秸秆的最优酶解条件,通过动力学研究评价了纤维素酶负荷、反应时间、基质浓度对还原糖产量的影响,并利用响应面分析法优化了酶解反应温度、pH值和转速。结果表明,最适的酶解糖化条件为：酶负荷30 FPU/g,基质浓度20 g/L,反应时间48 h,pH 4.8,转速200 r/min,反应温度49℃。在此条件下,秸秆的还原糖产量达到（0.479±0.012）g/g。     

蒸汽爆破预处理和微生物发酵对玉米秸秆降解率的影响

为了提高玉米秸秆的利用效率,首先对玉米秸秆进行蒸汽爆破预处理（压力2.5 Mpa,维压200 s）,然后再进行米曲霉发酵,研究物理和生物学处理对秸秆成分及相关酶活变化的影响。结果表明,蒸汽爆破使秸秆中纤维素、半纤维素和木质素的降解率分别达到8.47%、50.45% 和36.65% （p＜0.05）。爆破预处理的秸秆再经米曲霉发酵6 d后,秸秆中纤维素和半纤维素的降解率分别为27.89%和64.80% （p＜0.05）,发酵秸秆中的滤纸酶、羧甲基纤维素酶、淀粉酶和蛋白酶活力分别达到335.10、1138.92、1954.20和201.99 U/g。爆破预处理后进行米曲霉发酵,对于提高玉米秸秆的降解率具有非常重要的意义。     

“绿色革命”以来大气CO2浓度升高对C3作物营养品质的影响

自20世纪60年代"绿色革命"以来,育种技术和农耕技术的发展促进了农作物产量的大幅提升,然而作物的营养品质出现下降趋势。在相似的遗传背景下,大气CO_2浓度升高会使单位体积农作物产品的营养元素含量下降,因此"绿色革命"至今,农作物产品的营养元素下降可能受大气CO_2浓度升高影响。通过植物生长箱模拟"绿色革命"初期和目前的大气CO_2浓度水平(310μmol/mol和400μmol/mol),针对主要C_3作物水稻、小麦和大豆,研究"绿色革命"以来大气CO_2浓度升高对其籽粒的C、N、Fe、Zn元素含量的影响,结果表明:CO_2浓度升高对3种作物籽粒的C元素含量几乎没有影响,变化幅度在±1.5%之间;籽粒的N、Fe、Zn元素含量普遍呈现下降趋势,但均未达到显著水平。     

Potential of wild species for genetic enhancement of some semi-arid food crops

Discovery and incorporation of genes from wild species provide means to sustain crop improvement, particularly when levels of resistance in the cultigens are low and virulent strains of pests and pathogens overcome the host plant resistance. The extent of utilization and the potential of the wild genepool for genetic enhancement were reviewed in five important food crops viz. sorghum, pearl millet, chickpea, pigeonpea and groundnut grown in the semi-arid tropics. Introgression from compatible wild germplasm in the primary gene pool resulted in transfer of new cytoplasmic male sterility systems in pearl millet and pigeonpea, development of high protein, cleistogamous flower and dwarf pigeonpea lines and foliar disease resistant groundnut cultivars. Utilization of wild species in secondary and tertiary gene pools has been generally limited due to sterility, restricted recombination or cross incompatibility. Nevertheless, these species are extremely important as they contain high levels of resistance to several important biotic and abiotic stresses. Several of them, like those belonging to the Parasorghum section and the rhizomatous Arachis species are sources of multiple resistances and hold great promise to sustain crop productivity.     

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     

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.     

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.     

Collection and preliminary evaluation of native turfgrass accessions in Italy

Despite a raising interest on turfs in Italy, all theavailable varieties of this kind in the Country are of foreign origin, and areoften poorly adapted to the prevailing climatic conditions. This prompted tobegin a collection activity of indigenous turfgrass species, with the ultimategoal of identifying promising materials for future breeding based on localgenetic resources. The collection was carried out in three areas of Italy, viz.the northern Po Plain, the coastal region of Liguria, and the island of Sardiniathat are characterised, respectively, by subcontinental, warm temperate, andtypical Mediterranean climate. Altogether, 141 sites were visited, yielding 226accessions belonging to eight species of potential interest for turfs:Poa pratensis, Poa trivialis,Festuca rubra, Festuca arundinacea,Lolium perenne, Agrostis stolonifera,Agrostis tenuis, and Cynodon dactylon,this last being a warm-season grass. Poa pratensis andCynodon dactylon were mostly collected in northern Italyand Sardinia, respectively, whereas Festuca arundinacea andLolium perenne were rather ubiquitous. The collection sitesranged from 0 to 1040 m asl, but sites over 750 m wereonly visited in the inner part of Sardinia. All the accessions, collected aswhole plants, were transplanted at Lodi, northern Italy, where they are beingevaluated. Their preliminary evaluation for traits of importance for turf use,such as sward colour and overall quality, highlighted the great variation andthe occurrence of interesting accessions in all species. Other characters wererecorded, bearing specific importance in individual species, and in all casespromising accessions were identified. The germplasm of Festucarubra, Festuca arundinacea, and Loliumperenne proved highly infected by endophytic (symbiotic) fungi of thegenus Neotyphodium.     

Enhanced establishment and growth of giant cardon cactus in an eroded field in the Sonoran Desert using native legume trees as nurse plants aided by plant growth-promoting microorganisms and compost

To evaluate the feasibility of long-term desert reforestation technology of mixed vegetation, cardon cactus (Pachycereus pringlei) seedlings from indoor and outdoor nurseries were planted in the field adjacent to one seedling of potential legume nurse trees: mesquite amargo (Prosopis articulata), yellow palo verde (Parkinsonia microphylla), and blue palo verde (Parkinsonia florida). Some of the planting holes were also supplemented with common dairy compost. Additionally, the combinations of legume tree–cactus were inoculated with either a consortium of desert arbuscular mycorrhizal (AM) fungi, plant growth promoting bacteria (PGPB; the diazotroph Azospirillum brasilense Cd, and the phosphate solubilizer Paenibacillus sp.), or a mixture of all. The field experiments were evaluated periodically during 30 months for survival and growth. Cardons reared in an outdoor screen house survived better in the field than those reared in a controlled growth chamber and hardened later outdoors. Association with any legume nurse tree increased survival and enhanced growth of untreated cardons. For cardons growing alone, application of either compost, AM fungi, and all the treatments combined increased survival. For these plants, no treatment affected plant growth during the first 3 months after transplanting. Later, all treatments, except for AM fungi, enhanced plant growth. However, only 2 years after transplanting the enhanced growth effect of AM fungi was also significant. In the presence of the legume nurse trees, transient positive effects on cardon growth were recorded. General evaluation after 30 months of cultivation showed that the treatments positively affected cardon growth when growing alone or in combination only with mesquite amargo but not with the other two legume trees. This study proposes that young legume trees have the capacity to enhance survival and growth of cardon cactus, depending on the legume cactus combination. Additional treatments such as compost or PGPB can either amplify the effect or else attenuate it.     

Karyotypic and genome size variation in Cajanus cajan (L.) Millsp. (pigeonpea) and some wild relatives

Detailed karyotypes and 4C DNA amounts have been studied in five cultivars of Cajanus cajan and 20 species belonging to Cajanus, Rhynchosia, Dunbaria, Flemingia and Paracalyx. C. cajan shows intraspecific variability and its karyotype is most similar to that of C. cajanifolius (sect. Cajanus) in the morphology and number of satellite chromosomes and the lack of any correlation between chromosome size within the complement and asymmetry. Karyotypes of C. lineatus and C. sericeus belonging to sect. Atylia are similar with respect to maximum r-index and the ratio of longest and shortest chromosomes in their respective complements. C. acutifolius (sect. Frutocosa) is distinct in having a very low ratio (1.44) between the longest and the shortest chromosomes, while in C. albicans, C. goensis, C. scarabaeoides (sect. Cantharospermum) there is no chromosome pair with r-index >2.0. C. mollis and C. volubilis (sect. Volubilis) show similarity with regard to ratio between the longest and the shortest chromosomes and a distinct chromosome pair with an arm ratio of 2.7 and C. platycarpus is distinct (sect. Rhynchosoides) in having the smallest ratio (1.36) between the longest and the shortest chromosomes. 4C DNA amounts in Cajanus and Rhynchosia vary between 3.28 pg to 11.69 pg and 4.92 pg to 11.13 pg respectively, while in Dunbaria, Flemingia and Paracalyx these vary between 4.70 and 7:06 pg. In the genus Cajanus karyotypic features and 4C DNA amounts agree with the sectional classification and bring out a close relationship between C. cajan and C. cajanifolius. This is supported by studies based on seed protein patterns, isozyme analysis, trypsin and chymotrypsin inhibitor patterns, RFLP and RAPD data and crossability relationships. A clear relation between DNA amount and abnormalities effecting the extent of pairing and recombination in interspecific hybrids shows the importance of this study in developing future breeding programme involving C. cajan and its wild relatives that are of potential value.     

Effect of some fungicide seed treatments on the survival of Bradyrhizobium japonicum and on the nodulation and yield of soybean [Glycine max. (L) Merr.]

Several commercial fungicide seed treatments were evaluated for their possible effect on the survival of Bradyrhizobium japonicum on seeds and on the nodulation and yield of soybeans in a greenhouse and a field experiment. quinolate Pro (carbendazim and oxine copper), Vitavax 200FF (carboxin and thiram), and Monceren (pencycuron) had a small effect or no effect on the survival of B. japonicum and on the nodulation and yield of soybeans. They can thus be considered compatible with soybean seed inoculation. Germipro UFB (carbendazim and iprodione), Apron 35J (metalaxyl), and Tachigaren (hymexazol) decreased B. japonicum survival and the nodulation and yield of soybeans and thus cannot be considered compatible with soybean seed inoculation.     

Leaf position and genotype differences for mineral element concentrations in sorghum grown on tropical acid soil 1

Mineral element deficiencies and toxicities are common problems associated with sorghum [Sorghum bicolor (L.) Moench] production on acid soils. To better understand some of the mineral element problems and the analysis of plant tissue of sorghum plants grown on acid soils, four sorghum genotypes were grown on an acid Oxisol at Carimagua, Colombia limed with dolomite at 2 and 6 Mg ha^‐1.

Samples for mineral element analyses were obtained from leaves at different positions on the four genotypes. Concentrations of P and Mg were highest in the flag leaf (Leaf No. 1) and decreased as the position on the plant declined from the top of the plant for plants grown at 2 Mg lime ha^‐1. Similar decreases in P, Mg, K, and Zn concentrations occurred in plants grown with 6 Mg lime ha^‐1. Concentrations of Ca, S, Si, Mn, Fe, Cu, and Al increased as leaf position declined from the flag leaf for plants grown at 2 and 6 Mg lime ha^‐1. The higher lime supply enhanced Ca and reduced Mn and Fe concentrations in leaves. Differences in mineral element concentrations for the four genotypes used were fairly extensive. The elements to show the greatest range among genotypes were Al and Si and the elements to show the least range among genotypes were P, K, and S. Care should be used in collecting leaf samples for plant analysis and genotypic differences for accumulation of mineral elements should be considered in interpretation of results.