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碱性纤维素酶发酵条件的研究 总被引:2,自引:0,他引:2
采用芽孢杆菌Bacillus sp.AC-2作为碱性纤维素酶的生产菌株,对其发酵条件进行了研究。适宜的种子茵龄为24h;适于产酶的培养温度为37℃,培养基初始pH值10.5;在碳源和氮源分别为1%的淀粉和2%的豆饼粉时,碱性纤维素酶活力可达到76.04U/mL。该酶反应的最适温度为60℃;酶液在70℃以下、pH值6.0~10.0范围内稳定。该酶制剂在棉织物洗涤和纸浆脱墨方面具有良好的应用前景。 相似文献
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《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
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从毛竹根际分离到36株固氮菌,经初步镜检其中17株菌为芽孢杆菌,进一步鉴定确定其主要为多粘芽孢杆菌(Bacilluspolymyxa)和地衣芽孢杆菌(Bacilluslicheniformis),本文主要就其中菌号为G-8、G-12、G-14、G-17四株地衣芽孢杆菌的鉴定及固氮特性进行研究。结果显示:四株菌均为杆状,具芽孢孢孢囊稍膨大,它们的生理生化特性相同,但菌落形态有一些差异。G-8和G-17的最佳固氮温度为35℃左右,G-12和G-14的最佳固氮温度为30℃左右;G-12、G-8和G-14的最适固氮pH为6.0左右,G-17的最适固氮pH为6.0~7.5;四株菌都可利用碳源固氮,但均以葡萄糖为碳源时的固氮活性最高,依次为64.76、437.23、65.42、90.91nmolC2H4h-1,瓶-1。G-12在培养48h,G-8、G-14在培养96h,G-17在培养60h的固氮活性最高分别为138.50、122.01、170.87、109.81nmolC2H4.h-1.瓶-1。 相似文献
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摘要:研究了冬枣采后烂果上分离的3种主要病原细菌假单胞杆菌(Pesudomonas sp.)、黄单胞杆菌(Xanthomonas sp.)和欧氏杆菌(Erwinia sp.)对温度和pH值的耐受力。结果表明,假单胞杆菌的低温和高温耐受力分别为0℃和57.5℃;黄单胞杆菌的低温和高温耐受力分别为-2℃和55℃;欧氏杆菌的低温和高温耐受力分别为0℃和57.5℃。3种病原细菌对偏碱性环境耐受力较强,假单胞杆菌在pH值10时才停止生长,黄单胞杆菌和欧氏杆菌在pH值12时仍能生长;在酸性范围内,当pH值2~4时生长均受到抑制。pH、温度和时间复合处理的试验中,在pH值3~4,处理时间6~10min,假单胞杆菌处理温度在45℃,黄单胞杆菌在55℃,欧氏杆菌在50℃时,生长受到显著抑制. 相似文献
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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
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《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
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《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
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《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
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《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
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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
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《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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《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
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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
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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