山药多酚氧化酶部分特性的研究

采用分光光度法测定波长410nm处山药多酚氧化酶（PPO）的活性,研究了pH、温度、底物浓度、vmax和Km值以及抑制剂对山药PPO活性的影响．结果表明。山药PPO的最适pH=6．0,最适温度为35℃,底物浓度低于0．06moL·L^-1时。山药PPO活性与底物浓度呈线性关系,其Km=0．078moL·L^-1,Vmax=0．259（△OD·min^-1）,抑制剂柠檬酸、苹果酸、L-抗坏血酸对山药PPO活性均有抑制作用．     

国产固定化GL-7-ACA酰化酶制备7-ACA的工艺优化

通过对国产固定化GL-7-ACA酰化酶和游离酶的表观米氏常数(Km)及最大反应速度(Vm)的测定.结果表明:固定化GL-7-ACA酰化酶的Km和Vm值分别为8.69 mm o l.L-1和76μm o l.g-1m i-n 1,均较游离酶高;在对酶促反应的关键参数底物质量浓度、转化温度、转化pH进行优化后,用固定化GL-7-ACA酰化酶在底物GL-7-ACA质量浓度30 g.L-1、转化温度25℃、转化pH 8.0的条件下转化GL-7-ACA制备7-ACA可连续操作150批以上,转化率和收率均达95%以上.     

山药多酚氧化酶部分特性的研究

采用分光光度法测定波长410 nm处山药多酚氧化酶(PPO)的活性,研究了pH、温度、底物浓度、vmax和Km值以及抑制剂对山药PPO活性的影响.结果表明,山药PPO的最适pH=6.0,最适温度为35℃,底物浓度低于0.06 moL·L-1时,山药PPO活性与底物浓度呈线性关系,其Km=0.078moL·L-1,Vmax=0.259(△OD·min-1),抑制剂柠檬酸、苹果酸、L-抗坏血酸对山药PPO活性均有抑制作用.     

漆酶对酚类化合物生物催化氧化动力学研究——以儿茶酚和表儿茶素为模式底物

以白腐菌漆酶为试材,儿茶酚和表儿茶素为模式底物进行了酶促氧化反应动力学参数的测定。结果表明,以儿茶酚和表儿茶素为底物,漆酶催化氧化的产物最大吸收波长分别为388和408nm,作用最适pH值分别为5.5和5.75;最适反应温度均为55℃。漆酶对2种底物的催化氧化反应均符合米氏方程规律。在25℃反应条件下测得儿茶酚和表儿茶素2种底物的Km值分别为0.279和0.145mol/L;Vmax分别为0.114和1.139A/(U.min)。漆酶对表儿茶素的催化活性大大高于对儿茶酚的,作用于其混合物时需以儿茶酚的酶用量为准,即底物浓度0.5mol/L时加酶0.04U/mL。     

刺嫩芽采集加工过程中多酚氧化酶活性研究

以邻苯二酚为底物,采用分光光度法对采集的刺嫩芽鲜样及加工过程中各阶段的刺嫩芽产品进行多酚氧化酶（PP0）活性进行测定,测定结果是：刺嫩芽样品在同样温度及pH值条件下不同的腌制时间对多酚氧化酶活性大小有一定的影响,刺嫩芽由鲜样（样品1）至盐溃后期样品（样品2、样品3）的多酚氧化酶活性分别是：108．142U／g·min、31．714U／g·min、15．428U／g·min。酶活力单位定义为：在一定温度、pH值条件下1mmol／L底物浓度每分钟改变0．01吸光度所需的酶量为1个酶活力单位。     

选择性控制酶水解玉米芯木聚糖制备低聚木糖

对采用选择性控制木聚糖酶水解条件制备低聚木糖进行了研究，并同时探讨了以两种木聚糖形式——干粉和湿浆为原料造成的酶解结果差异及其原因。结果表明，目前较适宜的低聚木糖制备工艺为：以木聚糖湿浆为底物，底物质量浓度20～40g／L，酶用量1％（体积分数，下同），pH值4、8，温度50℃，酶解时间4h。造成干粉与湿浆酶解制备低聚糖结果差异的原因，可能是由于这两种底物自身结构特性的差异导致了底物可及度，以及酶与底物吸附作用的不同。结果显示当以干粉为底物，酶用量10％，酶解时间12h，低聚木糖得率最高可达40％（质量分数）左右，而以湿浆为底物，达到同样低聚糖得率的酶用量和酶解时间分别仅需1％和4h。     

Penidiella sp. HEY-1β-葡萄糖苷酶的分离纯化及其酶学性质

通过Penidiella sp. HEY-1发酵豆渣可制备产胞外β-葡萄糖苷酶(BGL)。粗酶液经过乙醇沉淀、DEAE-Sepharose Fast Flow离子交换层析和Sephadex G-100凝胶过滤层析等步骤后获得了凝胶电泳均一的BGL。通过SDS-PAGE测得其分子质量为65.5 ku。该酶反应的最适温度为60~70℃,最适pH值为3.0,在70℃以下及pH值2.0~8.0范围内均能保持稳定。Mn2+对酶有激活作用,而Na+对酶有抑制作用,其他金属离子对酶的活性影响不大。底物专一性实验表明,该酶可作用于对硝基苯-β-D-葡萄糖苷(p-NPGlu)、邻硝基苯-β-D-半乳糖苷(o-NPG)。作用于p-NPGlu和o-NPG的米氏常数(Km)值分别为0.434和0.411 mmol/L,酶促反应的最大速度(vmax)分别为1.0×10-3和3.3×10-4mol/(L.min)。     

膜荚黄芪苯丙氨酸解氨酶特性的初步研究

该文初步研究了荚膜黄芪苯丙氨酸解氨酶(PAL)的基本特性。结果表明:PAL的最适反应时间为30min,PAL在Tris-HCl缓冲液中适宜的pH值为8.0,最适反应温度为37℃,PAL酶浓度过高或过低不利于酶的活力,PAL最适底物浓度为2mmol/L。     

黑曲霉胞外耐高糖β-葡萄糖苷酶的分离纯化及部分特性研究

采用硫酸铵盐析、Phenyl Sepharose CL-4B疏水层析、DEAE-Sepharose阴离子交换层析、Sephacryl S-200凝胶过滤层析等步骤,从黑曲霉的发酵液中获得了凝胶电泳均一的两种β-葡萄糖苷酶。其中一种为耐高糖的β-葡萄糖苷酶,葡萄糖抑制系数(Ki)为41.01 mmol/L,纯化倍数和得率分别为56.7倍和22.66%。耐高糖β-葡萄糖苷酶单亚基分子质量为114.6 ku,以对硝基苯酚-β-D-葡萄糖苷(pNPG)为底物时,米氏常数(Km)值和酶促反应的最大速率(vmax)分别为0.904 mmol/L和1.08μmol/min。该酶最适反应温度60℃,最适反应pH值为4.0;在60℃以下及pH值3~7范围内均能保持稳定。所测定的化学试剂中,Ag 对酶具有较强的抑制作用,其它金属离子及乙二胺四乙酸对酶的活性影响不大。甲醇、正丁醇有明显激活酶活性的作用,但乙腈、丙酮对酶的抑制作用明显。     

优化培养条件对提高香菇漆酶产量的研究

对香菇发酵产漆酶条件进行了优化并研究了部分漆酶性质。结果发现静置培养优于振荡培养;pH值≥5.6时香菇菌体基本无法生长,香菇最适生长及产酶pH值为3.5;20℃低温有利于香菇漆酶生长,但最适产酶温度是25℃;Cu2 浓度为0.2~1.0 mmol/L时有利于香菇漆酶的合成,其中0.4 mmol/L是香菇产漆酶的最佳铜离子浓度,当铜离子终浓度超过5 mmol/L时,严重抑制香菇菌丝的生长;除了2,5-二甲基苯胺之外,阿魏酸、愈创木酚、没食子酸、黎芦醇等诱导剂促进香菇合成漆酶的作用不明显,反而会抑制菌丝生长;Tween-80的加入不利于漆酶合成。香菇漆酶在60℃条件下保温1 h后仍残余了2%的活力;以2,2′-连氮-双(3-乙基苯并噻唑-6-磺酸)(ABTS)为底物的最佳反应温度是65℃,最适反应pH值为2.2(柠檬酸-磷酸氢二钠缓冲液体系)。     

Browsing Damage on Pine (Pinus sylvestris and P. contorta) by a migrating moose (Alces alces) Population in Winter: Relation to Habitat Composition and Road Barriers

In Scandinavia, moose (Alces alces L.) sometimes cause severe browsing damage to economically-important pine. Moose-vehicle accidents have spurred construction of fences along roads, and these may interfere with moose migration between summer and winter ranges, or the road alone may be a barrier. If this happens and moose build up along roads, landowners may suffer economically. Therefore, this study investigated whether roads, fences or other factors influence the use of young pine stands by moose. Eighty stands along roads in northern Sweden were evaluated in which individually-browsed branches were counted on 9972 pines. Moose browsing was not significantly related to birch (Betula pendula Roth, B. pubescens Ehrh.) density, nor did it differ between pines (Pinus contorta Douglas or P. sylvestris L.). However, increased pine density, site productivity and proximity to a highway were associated with increased browsing. Further large-scale studies are needed to understand moose habitat selection and the effects of roads.     

Effects of Root Freezing on the Physiology and Growth of Picea glauca,Picea mariana and Pinus banksiana Seedlings Under Different Soil Moisture Regimes

The root systems of 2-yr-old Picea glauca, Picea mariana and Pinus banksiana seedlings were submitted to various frost temperatures during an artificial frost to induce different levels of root damage. Frost-damaged and control seedlings were placed in a greenhouse under high and low soil moisture regimes. Seedling growth and physiology were evaluated periodically. Seedling survival was reduced when root damage reached levels of 60-80%. Root systems of all three species showed partial to total recovery by the end of the experiment. In general, root freezing damage caused reductions in seedling growth, with these reductions becoming less significant over time. Root damage had little to no effect on black spruce and jack pine seedling physiology, while white spruce CO 2 uptake decreased with increasing root damage. Shoot nitrogen content of all three species decreased slightly with increasing root damage.     

Stand Structure in Pine,Spruce and Deciduous Forests: A Comparison Between Finnish and Russian Karelia

This study investigated the stand structure in pine, spruce and deciduous forests in the border district of Finland and Russia. A total of 46 mature forest stands was selected as pairs, the members of each pair being as similar as possible with respect to their forest site type, age, moisture and topography. The stands were then compared between the two countries by means of basal areas and number of stems. The proportions of dominating tree species were 2-12% lower, and correspondingly the proportions of secondary tree species higher, in Russian forests. The density of the forest stock was also higher in each forest type in Russia. The forests in the two countries differed most radically in terms of the abundance of dead trees. The amount was two to four times higher in Russian deciduous and spruce forests, and in pine forests the difference was 10-fold. The stand structures indicated that Russian coniferous stands, in particular, were more heterogeneous than intensively managed pine and spruce stands in Finland.     

Growth and Terminal Bud Formation in Picea abies Seedlings Grown with Alternating Diurnal Temperature and Different Light Qualities

The root collar diameter and the height:diameter ratio are of particular importance in container-grown seedlings where a high density in the containers may produce spindly seedlings. Temperature regimes and light quality are known to affect plant growth. The aim of this study was to identify responses in Picea abies (L.) Karst. seedlings grown with light providing different red:far-red ratios and under temperature regimes with alternating day (DT) and night temperature (NT) from negative (DT < NT) to positive (DT > NT) difference (DIF) between DT and NT. Experiments were conducted in controlled environment chambers and in a daylight phytotron. Only limited thermoperiodic responses appeared in P . abies seedlings with respect to seedling height and dry weight accumulation. The formation of terminal buds, however, was clearly delayed in seedlings grown at negative DIF. The results indicate a requirement for day extension light that is high in far-red, to prevent terminal bud formation under natural short-day conditions. An extended study should be conducted to clarify the minimum level of light intensity and the optimal light quality needed to prevent terminal bud formation under natural short-day conditions.     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

Natural Regeneration in Clear-cuts: Effects of Scarification,Slash Removal and Clear-cut Age

The effects of soil scarification (mounding), slash removal and clear-cut age on the natural regeneration in clear-cuts was evaluated using data from four sites in southern Sweden. The treatments were carried out during a good seed and establishment year for birch ( Betula pubescens Ehrh. and B. pendula Roth). Scarification had the strongest positive effect on the density of naturally regenerated seedlings, especially in birch, but also in pine ( Pinus sylvestris L.) and spruce [ Picea abies (L.) Karst]. Slash removal had a positive effect on birch density. No statistically significant effect of clear-cut age was found. In addition, no statistically significant interactions between clear-cut age and scarification or slash removal were found. The ingrowth of field vegetation was the fastest in areas that were not scarified, less rapid in areas scarified on old clear-cuts, and the slowest after scarification in fresh clear-cuts. In conclusion, it may be possible to control the density of birch during a good establishment year for birch. If birch is desired, the best combination of treatments is to remove the slash and scarify; otherwise, these treatments should be avoided.     

Risk Perception Among Non-industrial Private Forest Owners

Based on an enquiry, risk perception among non-industrial private forest owners is described in relation to climate change and forestry hazards. Of the respondents, 11% took action to remedy the effects of climate change. Out of a given set, hazards were ranked according to each respondent's experience of recent substantial financial loss to the estate and in relation to his or her willingness to make investments aimed at risk reduction. For each hazard, the respondent assessed the risk in four classes ranging from very high to negligible risk. Six hazards were considered most problematic in all three aspects: browsing damage, falling timber prices, damage by wind, spruce bark beetle, root rot and pine weevil. A majority of the respondents claimed to take action to reduce the risk associated with at least one hazard, while 35% did not know whether they did. Excluding climate change, the need for decision support was the largest in relation to damage by wind owing to a combination of perceived high risk and a high level of ignorance in relation to whether risk-reducing measures were taken.     

Interactions in decomposition and N mineralization between tropical legume residue components

In situ produced plant residues contain a mixture of different plant components of varying quality. To assess synergistic or antagonistic interactions occurring during the decomposition and mineralization of such mixtures, individual plant parts (stems, leaves, leaf litter and roots) or the mixture of stems, leaves and leaf litter of the agroforestry species pigeonpea (Cajanus cajan) or of crop residues of peanut (Arachis hypogaea) or of the weed hairy indigo (Indigofera hirsuta) were incubated in pots for 19 weeks. Periodically, remaining plant residues were sieved out (>2 mm), weighed and N content as well as soil mineral N determined. Above- and below-ground residues of peanut decomposed fastest and showed the largest N release in agreement with their high N concentration and low-acid detergent fibre (ADF) : N ratio. Hairy indigo was hypothesized to be of lower quality than pigeonpea because of its high-polyphenol content. However, it decomposed faster than pigeonpea, largely because of the higher N and lower lignin concentration of its components. Ranking of individual plant components for N mineralization resulted in the following pattern, leaves > leaf litter > roots > stems. In mixtures of the different plant components a similar species order in decomposition was obtained, e.g. peanut > hairy indigo > pigeonpea. The amount of N released from the mixture was dominated by stem material that comprised 46–61% of the mixture. The interactions in mixtures were relatively small for peanut (generally high-quality components) as well as for pigeonpea (low proportion of high-quality components, i.e. N rich leaf material). However, a positive interaction occurred during later stages of N mineralization in the mixture of hairy indigo as it had a significant proportion of N rich components and absence of highly reactive polyphenols. Thus, for plants with low to intermediate chemical quality attributes, manipulating plant composition (e.g. by varying harvest age, affecting stem and leaf proportions) will be important to obtain significant interactions during decomposition when its components are mixed.     

Pasture production and tree growth in a young pine plantation fertilized with inorganic fertilizers and milk sewage in northwestern Spain

The use of organic waste materials such as milk sewage as an organic fertilizer could have the dual advantages of organic-waste disposal and reduced dependence on inorganic fertilizers. The effects of fertilization with (1) conventional mineral fertilization, (2) milk sewage sludge at 40 kg N ha⁻¹ target rate and (3) no fertilization on pasture production and tree growth were examined in an experiment consisting of two pasture mixtures under a one-year-old Pinus radiata plantation with a density of 2500 trees ha⁻¹. The two pasture mixtures were: (1) Dactylis glomerata L. var. saborto (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹); (2) Lolium perenne L. var. Tove (25 kg ha⁻¹) + Trifolium repens L. group Ladino (4 kg ha⁻¹) + Trifolium pratense L. var. Marino (1 kg ha⁻¹). The experiment began in the spring of 1995 using a randomized block design with three replicates in Castro Riberas de Lea (Lugo, Galicia, north-western Spain). Plot size was 12 × 8 m², with a 1 m buffer strip between plots. Two-year data showed that fertilization with either material had a positive effect on pasture production, with no significant difference between the two fertilization treatments. Tree growth in the milk sewage sludge plot was significantly higher than in the control plots. Inorganic fertilization increased pasture production, but affected tree growth negatively. The results show that milk sewage sludge could be used as a fertilizer in silvo-pastoral systems. This revised version was published online in June 2006 with corrections to the Cover Date.