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1.
用水不溶性燕麦木聚糖吸附分离绿木霉木聚糖酶,结果表明,该木聚糖能选择性吸附分离木聚糖酶组分,分离所得两组分均达到电泳纯.未吸附组分(XynⅠ)和吸附组分(XynⅡ)的分子质量分别为29.5和26.5ku,它们对桦木木聚糖的米氏常数分别为1.73和3.16g/L.以纯化酶组分及其混合物水解燕麦木聚糖,采用高效液相色谱分析相应的水解产物,结果表明,XynⅠ降解燕麦木聚糖时,主要降解作用发生在底物中没有取代基的区域,水解产物的聚合度较高;XynⅡ对底物具有更强的适应性,能降解底物中有取代基的区域,相对XynⅠ酶组分,XynⅡ酶组分对低聚合度的木聚糖的活性更高,木二糖为主要降解产物.木聚糖酶组分均为酸性酶,XynⅠ耐酸性范围更宽,而XynⅡ对pH值更为敏感;XynⅠ、XynⅡ的最适反应温度分别为45和55℃;而它们的适宜pH值分别为4.5和5.5. 相似文献
2.
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4 h.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12 h,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4 h. 相似文献
3.
《林业工程学报》2017,(4)
为寻求具有耐热性能的木聚糖酶,笔者以嗜热网球菌(Dictyoglomus thermophilum)DSM3960的基因组为模板,克隆得到木聚糖酶基因xyn B-DT,该基因全长1 083 bp,共编码361个氨基酸,蛋白的理论分子量约为40ku。通过NCBI数据库比对发现该基因编码的蛋白质属于糖苷水解酶G11家族。实现大肠杆菌异源表达重组木聚糖酶Xyn B-DT,通过IPTG诱导,酶活达到30.6 U/mL。该重组木聚糖酶的最适温度为85℃,在60~80℃范围内均有较好温度稳定性,在60℃条件下保温2 h,酶活维持在90%以上,在90℃下保温2 h,酶活尚残余约50%;最适pH为6.5,在pH为5.0~7.5范围内保温24 h仍可保留约90%剩余酶活力。该酶以Beechwood木聚糖为底物,米氏常数(K_m)和最大反应速率(V_(max))值分别为5.63 mg/mL和1.572 mmol/(L·min~(-1))。以玉米芯木聚糖为底物,研究XynB-DT水解玉米芯木聚糖的条件及产物,结果显示在温度70℃、pH 6.0条件下酶解12 h,加酶量为400 U/g,最终酶解得率为44.3%,玉米芯木聚糖的水解产物主要以木二糖和木三糖为主,表明该木聚糖酶在低聚木糖制备方面具有较大应用潜能。 相似文献
4.
耐热型木聚糖酶制备工艺的研究 总被引：1，自引：0，他引：1
以木糖渣为碳源，利用耐热子囊菌（Thermoascus aurantiacus)液体发酵生产木聚糖酶，确立了最佳工艺参数为：木糖渣质量浓度4％，培养温度45摄氏度，转速180r/min，培养基初始pH值4．8，初始C／N为7．1，木聚糖酶活性可达900U/mL。酶学性质研究表明，该酶反应的最适温度为75摄氏度，最适pH值为4．8，该酶的耐热性强，在75摄氏度下温保1h，酶活力剩余85％以上。 相似文献
5.
为充分利用杨树资源,以杨木加工废弃物杨木屑为原料,研究碱法提取木聚糖的工艺条件,并采取酶法制备低聚木糖。以质量分数为1%的稀硫酸预处理可以有效提高杨木屑木聚糖的得率,较对照组提高了2倍。对比3种碱液(NaOH、KOH和NaHCO_3)提取杨木屑木聚糖的得率,以NaOH提取的木聚糖得率最大。通过单因素和正交试验优化NaOH提取杨木屑木聚糖的条件,结果显示碱液质量分数10%,固液比1∶10(g∶mL),温度120℃下提取3 h所得的木聚糖得率可达到20.7%,且四因素对提取得率的影响显著程度依次为提取温度碱液质量分数提取时间固液比。碱法提取杨木屑木聚糖酸水解后产物由88.69%D-木糖、4.76%纤维二糖和6.62%葡萄糖组成且不含有阿拉伯糖,说明碱法提取的杨木屑木聚糖支链上主要连有木糖。以碱法提取杨木屑木聚糖为底物,优化了来源于嗜热菌Dictyoglomus thermophilum的重组木聚糖酶Xyn B-DT的酶解适宜条件:在温度70℃,pH 6.0,酶用量3.00 U/m L,反应时间12 h后,杨木屑木聚糖水解产物中以木二糖和木三糖为主,并含有少量木四糖,降解率达86.2%。研究结果为杨木屑木聚糖的高值化利用奠定了基础。 相似文献
6.
纸浆漂白用木聚糖酶的选择性合成 总被引：5，自引：2，他引：3
以里氏木霉(Trichoderma reesei) Rut C-30为产酶菌,研究了碳源、培养温度、初始pH值、碳氮比对木聚糖酶和纤维素酶合成的影响.结果表明,粗木聚糖和亚硫酸盐纸浆混合作为碳源有利于木聚糖酶和纤维素酶的合成;低温有利于木聚糖酶和纤维素酶的合成,但产酶时间较长,高温对木聚糖酶的合成有一定的影响,对纤维素酶的合成能有效地抑制,且产酶时间较短;初始pH值低有利于纤维素酶的合成,初始pH值高则延长了木聚糖酶的合成时间,且强烈抑制纤维素酶的合成;低碳氮比有利于纤维素酶的合成,高碳氮比使得木聚糖酶的合成滞后,能够有效抑制纤维素酶的合成.以粗木聚糖和亚硫酸盐纸浆混合作为碳源,调控培养温度、初始pH值和碳氮比能有效地促进木聚糖酶的合成,抑制纤维素酶的合成,致使木聚糖酶活与纤维素酶活的比值提高,从而有利于选择性合成纸浆漂白用木聚糖酶,调控培养方式为:提高碳氮比(7.2)和初始pH值(6.0),在培养初期(1 d)培养温度为35～36 ℃,中后期培养温度25～26 ℃,调控6 d后,木聚糖酶酶活和纤维素酶酶活分别为186.93和0.156 IU/mL,酶活比为1 198. 相似文献
7.
8.
分别研究了粗木聚糖酶和纯化的木聚糖酶在超滤膜反应器(UMR)和常规反应器(CSBR)中的酶解特性。粗木聚糖酶或纯木聚糖酶在UMR中酶解木聚糖时,反应进行了525 m in时所得产品中低聚木糖各组分的质量分数(木二糖~木五糖)均在20%左右,木糖质量分数约为9.5%。在UMR中粗木聚糖酶降解木聚糖时的低聚木糖得率、低聚木糖占总糖的比例和低聚木糖生产能力比纯木聚糖酶在CSBR中分别高19.1%、14.8%和13.5%;而木糖的得率却低55.2%。粗木聚糖酶在UMR中酶解木聚糖时,所得低聚木糖产品中木二糖~木五糖组分含量基本相等;纯木聚糖酶在CSBR中酶解木聚糖时,所得低聚木糖产品中木二糖含量较高。同纯木聚糖酶在CSBR中酶解特性相比,粗木聚糖酶在UMR中酶解木聚糖可以制得高质量低聚木糖。 相似文献
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10.
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。 相似文献
11.
《Scandinavian Journal of Forest Research》2012,27(5):427-435
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. 相似文献
12.
《Scandinavian Journal of Forest Research》2012,27(3):206-217
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. 相似文献
13.
《Scandinavian Journal of Forest Research》2012,27(1):53-61
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. 相似文献
14.
《Scandinavian Journal of Forest Research》2012,27(1):15-27
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. 相似文献
15.
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。 相似文献
16.
《Scandinavian Journal of Forest Research》2012,27(2):131-138
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. 相似文献
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18.
《Scandinavian Journal of Forest Research》2012,27(5):472-479
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. 相似文献
19.
Srisuda Thippayarugs Banyong Toomsan Patma Vityakon Viriya Limpinuntana Aran Patanothai Georg Cadisch 《Agroforestry Systems》2008,72(2):137-148
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. 相似文献
20.
A. Rigueiro-Rodríguez M. R. Mosquera-Losada E. Gatica-Trabanini 《Agroforestry Systems》2000,48(3):245-256
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. 相似文献