利用汽爆玉米芯酶解液发酵生产类胡萝卜素的研究

研究了汽爆玉米芯酶水解及酶解液发酵生产类胡萝卜素.对影响酶解各因素考察表明:在最适酶解条件下,即温度50℃、pH值4.8、底物质量浓度50 g/L、加酶量48 FPU/g、酶解时间60 h,还原糖质量浓度达34.85 g/L.利用均匀设计对发酵条件进行了优化,最优发酵条件为:装液量23.91 mL,pH值4.85,接种...     

海藻酸铝固定化酵母生产酒精的研究

以树干毕赤酵母（Pichia stipitis)为发酵菌株，利用海藻酸铝凝胶代替海藻酸钙，可明显延长固定化酵母的使用寿命，海藻酸铝凝胶耐磷酸盐能力是海藻酸钙凝胶的3倍，海藻酸铝树干毕赤固定化增殖酵母细胞可同步发酵戊糖己糖，以混合糖质量浓度60g/L(50%葡萄糖，50%木糖）为发酵底物，成熟醪中酒精质量浓度由26.0g/L提高到27.3g/L，总糖利用率为93.7%。     

树干毕赤酵母戊糖发酵影响因素的研究

研究了树干毕赤酵母(Pichia stipitis)CBS 5776以木糖为单一碳源发酵生成乙醇的影响因素.结果表明,树干毕赤酵母发酵体系的初始酵母质量浓度、pH值和通风条件对其发酵性能有很大影响,发酵的最佳初始酵母质量浓度为5～7 g/L,最佳pH值范围是4.7～5.5,250 mL摇瓶发酵的最佳持液量为75 mL,最佳摇床转速为150 r/min.在2L发酵罐中,通风量为0.075 L/min,即0.05L/(L·min)时,发酵时间为32 h,最高乙醇质量浓度18.29 g/L,乙醇得率83.2％;厌氧发酵的最高乙醇质量浓度19.09 g/L,乙醇得率86.5％.因此,最优通风量为0～0.075 L/min.pH值的提高和通风条件的改善可以使酵母对乙酸的耐受能力得到提高,在150 r/min的转速、pH值为5时,提高通风量后,酵母乙醇得率比厌氧时提高了166.6％.纯糖实验得到的结果用以玉米秸秆酸性爆破模拟水解液定向驯化的酵母在含有乙酸的模拟糖液中发酵得到验证.     

固定化混合菌利用戊糖和己糖共发酵制备乙醇

为研究固定化混合菌种对戊糖和己糖同步发酵生产燃料乙醇的影响,以海藻酸钙为固定化载体,采用包埋法固定化休哈塔假丝酵母(Candida shehatae)和酿酒酵母(Saccharomyces cerevisiae)混合菌发酵生产燃料乙醇,并对固定化混合菌种的发酵条件进行优化。结果表明:固定化混合菌种发酵可以快速利用葡萄糖,解除葡萄糖代谢对木糖代谢的抑制作用,提高发酵效率,发酵时间从固定化单菌发酵的24 h缩短至20 h,发酵时间缩短16.67%。乙醇产量从13.28 g/L增加至14.89 g/L,升高了12.12%。固定化混合菌种的优化条件为:混合糖(葡萄糖和木糖)质量浓度为45 g/L,发酵温度为30℃,摇床转速为170 r/min,休哈塔假丝酵母和酿酒酵母菌体的比例为4∶1。在此条件下得到最佳乙醇产量为15.21 g/L,较优化前(13.74 g/L)提高了10.70%。本研究结果可为固定化混合菌发酵生产燃料乙醇的工业化提供理论依据。     

介孔氧化钛与海藻酸钠固定化木聚糖酶的对比研究

为了提高木聚糖酶在应用过程中的稳定性,以介孔氧化钛和海藻酸钠为载体,开展木聚糖酶固定化研究。氧化钛固定化木聚糖酶,考察了吸附时间、给酶量、温度和pH值对固定化的影响;海藻酸钠固定化木聚糖酶,考察了NaCl浓度、海藻酸钠浓度和硬化时间对固定化的影响。在此基础上,对比两种固定化木聚糖酶的稳定性。研究结果表明,优化的介孔氧化钛固定化条件为:固定化时间0.5 h,给酶量20.36 IU/g,温度65℃,pH值6.0,固定化木聚糖酶回收率为93.37%;优化的海藻酸钠固定化条件为:硬化时间2 h,氯化钙质量浓度为20 g/L,海藻酸钠质量浓度为35 g/L,温度65℃,pH值6.0,固定化木聚糖酶回收率为28.77%。相对于海藻酸钠固定化木聚糖酶和游离木聚糖酶,介孔氧化钛固定化木聚糖酶热稳定性和酸碱稳定性均优于海藻酸钠固定化木聚糖酶及游离木聚糖酶。     

微生物发酵制备沙棘果浆酵素的研究

笔者针对沙棘果浆筛选合适的微生物发酵剂,并探究试验条件下最佳的发酵工艺,为沙棘产品的开发提供依据。结果发现,沙棘原浆可溶性还原糖含量为17.2 mg/mL,总酸含量为26.90 g/L,总黄酮含量为7.294 mg/mL.沙棘果泥酵素发酵工艺采用酵母菌和乳酸菌混合菌发酵方式,酵母菌粉的接种量为0.01%,乳酸菌粉的接种量为0.1%,发酵条件为37℃,发酵40 h效果最佳。经40 h发酵后,沙棘中可溶性还原糖含量为2.481 mg/mL,总酸含量为20.493 g/L,总黄酮含量为11.187 mg/mL.     

稻草液化物酶解发酵制备2,3-丁二醇的研究

以乙二醇为液化剂对稻草进行液化和酶解预处理,经肺炎克雷伯氏菌(Klebsiella pneu-moniae CICC 10011)发酵制备2,3-丁二醇。考察了温度、pH值、接种量、摇床转速、时间和底物浓度对发酵产2,3-丁二醇的影响。结果表明:稻草液化产物酶解后,经双膜浓缩总糖质量浓度可控制在85～95 g/L,不但为后续发酵提供充足的碳源,而且实现了工艺控制的自动化,易于提高产物浓度,降低分离成本。对其脱色发酵生产2,3-丁二醇,最佳发酵条件为:初始总糖质量浓度94.3 g/L、37℃、pH值5.5、接种量10%、转速170 r/min、反应72 h,制得2,3-丁二醇质量浓度为36.47 g/L,2,3-丁二醇对总糖的转化率可达42.5%,生产效率为0.51 g/(L.h),对其液化产物的转化率最高为33.4%。     

基因重组酵母发酵木糖产酒精的研究

以一株基因重组酵母为研究对象,探讨了厌氧条件下pH值、底物浓度、接种量、乙酸质量分数和葡萄糖添加量等关键因子对木糖发酵的影响。结果表明,重组酵母Saccharomyces cerevisiae ZU-10有较强的发酵木糖产乙醇的能力,在80g/L(相对木糖)、初始pH值5.5、接种量1.2g/L(细胞干质量,相对培养液)、30℃下发酵72h,发酵液中乙醇质量浓度达到28.9g/L。发酵液中的乙酸质量分数低于0.05%时对发酵木糖影响不大。添加适量的葡萄糖可促进木糖发酵,在30g/L木糖培养液中添加40g/L葡萄糖,36h内木糖利用率从79.0%增加到85.7%。     

Klebsiella oxytoca发酵木糖生产2,3-丁二醇的研究

利用一株克雷伯氏菌(Klebsiella oxytoca ZU-03)发酵木糖生产2,3-丁二醇,并对主要发酵工艺参数进行了优化.实验结果表明:在木糖质量浓度 90 g/L、玉米浆质量浓度 6 g/L、接种量 10 %(体积分数)、初始pH值5.5、 30 ℃的条件下发酵 96 h,木糖利用率为 89 %, 2,3-丁二醇的质量浓度为 36.22 g/L,得率为 0.45 g/g,达到了理论值的 90 %.     

酶法糖化玉米芯发酵生产乙醇的研究

研究了玉米芯的酶法水解及酶解液的乙醇发酵。采用里氏木霉ZU-02纤维素酶水解酸预处理后的玉米芯为原料,适宜的酶用量为20 FPIU(以每克底物计,下同),48 h后酶解得率为67.5%;添加黑曲霉ZU-07所产纤维二糖酶可有效解除纤维二糖累积引起的反馈抑制作用,当纤维二糖酶用量为6.5 CB IU时,48 h后酶解得率提高到83.9%。采用分批补料酶解工艺,使底物质量浓度提高到200 g/L,酶解60 h后还原糖质量浓度达到116.3 g/L,酶解得率为80.1%。利用一株耐高温酿酒酵母HTR-11在38℃下对酶解液进行乙醇发酵,质量浓度95.3 g/L的葡萄糖在18 h内发酵生成质量浓度为45.7 g/L的乙醇,其得率达到理论值的94%。     

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。     

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.     

Key Habitats in the Norwegian Production Forest: A Case Study

This study investigated the forest history, structural characteristics, the presence of fungal species suggested to indicate ecological continuity in old-growth forest, and the species composition of saproxylic beetles in 30 old forest ''woodland key habitats'' (WKHs), and compared them with production forest in the same age-class in south-eastern Norway. No statistically significant differences in forest characteristics, community of saproxylic beetles or number of red-listed beetles were found between the WKHs and the production forest, probably owing to a combination of profound long-term logging and a lack of will to delineate sufficiently large WKHs in the one area with significantly less forestry impact. The study indicates the advantage of including forest history information in WKH selection where such data exist, and the importance of restoring habitats in heavily exploited forest landscapes.