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941.
Physicochemical properties of pretreated poplar feedstocks during simultaneous saccharification and fermentation 总被引:2,自引:0,他引:2
Lisbeth Meunier-Goddik Michelle Bothwell Kunruedee Sangseethong Kuakoon Piyachomkwan Yun-Chin Chung Khamphet Thammasouk Djuhartini Tanjo Michael H. Penner 《Enzyme and microbial technology》1999,24(10):77-674
Physicochemical properties of native and dilute acid pretreated (0.6% H2SO4, 10 min, and either 170°C or 180°C) poplar were investigated before and during simultaneous saccharification and fermentation (SSF). SSF duration was 5 days and employed Trichoderma reesei cellulases and Saccharomyces cerevisiae fermentation. Chemical composition (glucan, xylan, lignin), enzyme-accessible surface area (based on solute exclusion), crystallinity index, particle size distribution, particle shape, and enzyme adsorption (cellulase, β-glucosidase) were compared to cellulose conversion. Cellulose conversion varied from 8% for native poplar to 78% for the 180°C-pretreated poplar. The physicochemical properties of native poplar changed little during SSF. In contrast, the physicochemical properties of the 180°C-pretreated feedstock changed markedly. Enzyme-accessible surface area and β-glucosidase adsorption increased by 83% and 65%, respectively, as cellulose was removed from the feedstock. Crystallinity index and particle size (large fraction) decreased by 65% and 93%, respectively. Cellulase adsorption per unit weight increased initially (+45%) followed by a slight decrease (−13%). The same trends were observed, although to a lesser extent, for 170°C-pretreated feedstock. 相似文献
942.
The relationships between drought response and anatomical/physiological properties were assessed in two poplar clones belonging
to the Aigeros section: Populusxeuramericana clone Dorskamp (drought-tolerant) and clone Luisa Avanzo (drought-sensitive). Cuttings of both clones were exposed for 12
h to 0 mM (control). 50 mM (osmotic potential −0.112 MPa), and 150 mM (−0.336 MPa) mannitol. In control, Dorskamp had smaller
stomata than Luisa Avanzo, one or two layers of palisade cells, a spongy mesophyll, and high concentrations of antioxidative
compounds (ascorbate, glutathione). After exposure to 50 or 150 mM mannitol, both clones closed their stomata: leaf conductance
and opening of stomata decreased. When exposed to 50 mM mannitol, net photosynthetic rate (P
N) and chlorophyll (Chl) and total solute contents remained stable; ribulose-1,5-bisphosphate carboxylase/-oxygenase activity,
Chl synthesis and turn-over, ascorbate peroxidase and glutathione reductase activities were less affected in Dorskamp than
in Luisa Avanzo. Following an exposure to 150 mM mannitol, Dorskamp exhibited higher P
N and higher contents of antioxidants (ascorbate, glutathione) and antioxidative enzymes (ascorbate peroxidase, glutathione
reductase) than Luisa Avanzo. Hence the drought-tolerant poplar was able to better avoid and tolerate osmotic stress.
This revised version was published online in June 2006 with corrections to the Cover Date. 相似文献
943.
The effects of commercial forestry harvest and regeneration practices (clearfelling and slash-burning) on the lucanid fauna of the wet sclerophyll forests of southern Tasmania and the dry sclerophyll forests of eastern Tasmania were examined using pitfall catches. Lucanids are saproxylic beetles, dependent on dead, moribund and decaying wood. Samples taken from old-growth forest and from a chronosequence of sites regenerating after logging, in each forest type, were used to compare the species richness and abundance of the lucanid assemblages. In both forest types, species richness and abundance was highest in the youngest regeneration sites (1–3 year), reflecting the species richness of the original and adjacent unlogged forest, lowest in the older (20–25 year) sites, and variable in the old-growth sites. TWINSPAN cluster analysis showed no clear distinction between regeneration and old-growth forest. The post-harvest slash and stump residue provided an important refugium and initial habitat, but our research indicates that some species may not maintain populations in the long term. Our results suggest that most species of lucanids will find a continuous supply of suitable habitat only in old-growth forests; and such species may become less common as clearfell harvesting leads to a replacement of heterogeneous old-growth forest with single-aged monospecific stands. Continuity of supply of wood in all decay stages, the maintenance of sufficient source areas, and biological connectivity between old-growth stands to enable dispersal, are all likely to be essential to maintain lucanid beetle community integrity. If similar principles apply to other saproxylic species of invertebrate, then clearfelling and slash-burning may cause a gradual extinction of an important element of the forest biota. 相似文献
944.
Rearing of the colydiid beetle predator, Dastarcus helophoroides, on artificial diet 总被引:6,自引:0,他引:6
Artificial diets for the colydiid beetle, Dastarcus helophoroides, a predator of cerambycid beetles and xylocopid bees, were evaluated. Hatched larvae were reared on artificial diets composed of silkworm pupa-powder, dry yeasts, yeast extract, sucrose, peptone, squid liver oil, preservatives and distilled water, but their emergence rate was very low. If larvae were fed paralyzed cerambycid larvae till they became approximately 8 mm in body length and then reared on artificial diet, emergence rates were high. Using the latter method, mass-production of this colydiid beetle is feasible. 相似文献
945.
以气体交换测定结合叶绿素荧光技术对几个杂种杨新无性系在自然光胁迫下的光合生理生态特性进行分析。8月CO2气体交换测定显示,中午存在明显的光合作用下降现象,同时某些无性系中午的气孔导度也有不同程度下降。叶绿素荧光分析显示,强光胁迫会影响光合作用的原初光化学反应过程,光系统Ⅱ(PSII)反应中心的最大光化学量子产率,有效光化学量子产率等反映光系统Ⅱ反应中心活性的参数值在中午均比早晨低。与此同时,光系统Ⅱ反应中心的非光化学淬灭上升,他是光系统Ⅱ反应中心的一种自我保护机制。参数(Fm-Fmr)/Fmr、1—qp/qN和(F’m-F)/F’m可以反映各个无性系发生光抑制的可能性大小。由此计算出的各无性系发生光抑制的可能性排列次序与气体交换法测定的结果是一致的。 相似文献
946.
947.
948.
949.
研究了冬小麦-夏玉米→春玉米轮作中,长期施用磷肥、有机肥对土壤总磷库、无机磷库的影响及磷肥的产量效应.结果表明,长期施用磷肥、有机肥土壤全磷、总无机磷均有不同程度的积累,土壤磷素的积累以无机磷为主.根据土壤磷素的收支平衡状况,计算出维持土壤磷素收支平衡磷肥的临界用量:冬小麦-夏玉米种植年份为P2O594.7kg·hm-2,春玉米种植年份为P2O551.5kg·hm-2.根据肥料效应函数计算出磷肥(P2O5)的经济最佳、最高产量用量分别为:冬小麦-夏玉米种植年份为135.8、149.8kg·hm-2,春玉米种植年份为88.6、95.9kg·hm-2. 相似文献
950.
报道了一种具混合型纹孔(互列式纹孔和对列式纹孔)的化石本。化石木产自内蒙古乌达矿区老石旦矿附近太原组上部,地质时代为早二叠世早期。经比较,确认为南洋杉型木属(Araucarioxylon Kraus)一种新;老石旦南洋杉型木(Araucarioxylon laoshidanense sp.nov.).根据混合型纹孔的存在及其他特征,认为新种可能代表了一种原始的松杉类植物的木材化石。主要特征:仅保存 相似文献