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《林业工程学报》2017,(4)
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。 相似文献
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以水洗稀酸蒸汽爆破玉米秸秆(ASC)得到的预水解液为原料,分析了ASC预水解液中可发酵性糖、碳水化合物降解产物和主要木质素降解产物的含量,研究了ASC预水解液乙醇发酵性能、3种脱毒方法对预水解液进行脱毒及乙醇发酵性能。研究结果表明,ASC预水解液中可发酵糖类主要含有木糖(49.50 g/L)及少量葡萄糖(9.80 g/L),可用于发酵制备乙醇,但含有大量抑制物不利于乙醇发酵,发酵60 h时的糖利用率和乙醇得率分别仅有87.96%和74.63%。ASC预水解液经过乙酸乙酯萃取、酵母吸附和亚硫酸钠处理3种方式脱毒后乙醇发酵性能均得到较大改善:经乙酸乙酯萃取脱毒后发酵36 h时的糖利用率和乙醇得率分别为95.40%和90.71%;经酵母吸附脱毒后发酵48 h时的糖利用率和乙醇得率分别为97.83%和81.98%;经亚硫酸钠处理脱毒后发酵48 h时的糖利用率和乙醇得率分别为95.55%和84.74%。虽然乙酸乙酯萃取脱毒效果最佳,但从工业应用前景来看,酵母吸附和亚硫酸钠处理是最佳选择。 相似文献
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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. 相似文献
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《林产化学与工业》2015,(6)
以玉米秸秆为原料,研究稀硫酸-氢氧化钙联合预处理秸秆制备燃料乙醇的方法。玉米秸秆经稀硫酸预处理、固液分离后得到的预水解液(主要含有木糖)进行戊糖发酵;而残渣采用氢氧化钙进一步预处理后,经酶水解得到的葡萄糖进行己糖发酵,从而实现戊糖和己糖分开发酵产乙醇。研究结果表明,玉米秸秆稀硫酸预处理最佳条件为:硫酸用量1.00%(以绝干玉米秸秆计),反应温度130℃,反应时间70 min,此时木聚糖水解得率为80.45%;采用树干毕赤酵母对玉米秸秆稀硫酸预水解液原液、浓缩液Ⅰ(浓度为原液的2倍)和浓缩液Ⅱ(浓度为原液的3.5倍)进行戊糖发酵,乙醇得率分别为82.52%、85.13%和73.64%。氢氧化钙进一步预处理玉米秸秆稀硫酸预处理渣的最佳条件为:氢氧化钙用量0.125 g/g(以绝干玉米秸秆计),反应温度90℃,时间24 h,此时纤维素酶水解得率为84.92%;采用酿酒酵母对两步预处理残渣的酶水解液原液、浓缩液Ⅲ和浓缩液Ⅳ(浓度为原液的2倍和3倍)进行己糖发酵,乙醇得率分别为92.22%、91.89%和85.54%。 相似文献
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比较研究休哈塔假丝酵母单菌发酵、休哈塔假丝酵母和酿酒酵母两步发酵、休哈塔假丝酵母和酿酒酵母同步发酵3种发酵模式下对混合糖(葡萄糖和木糖)的利用情况,结果显示2种酵母同步发酵能够有效解除葡萄糖的抑制,加快木糖利用速率。采用Plackett-Burman实验、最陡爬坡实验和中心组合设计,对2种酵母混菌利用戊糖己糖发酵生产乙醇的培养基进行优化,得到最优培养基条件:硫酸铵9.09 g/L、磷酸二氢钾8.96 g/L、氯化钙0.34 g/L,在此条件下发酵得到乙醇产量为21.71 g/L,较优化前(19.85 g/L)提高了9.4%;混菌在优化后的培养基下进行发酵,酵母浊度OD由12.12增长到了21.87,木糖利用率由优化前的82%增长到优化后的93%。 相似文献
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《林产化学与工业》2015,(4)
针对己糖(葡萄糖)、戊糖(木糖)共发酵产纤维素乙醇抑制物控制的关键性瓶颈,分别以玉米秸秆及玉米秸秆中非木质素的4类组分纤维素、半纤维素、热水提取物和乙醇提取物为原料,并以0.75%稀硫酸和180℃预处理40 min得到5种稀酸预处理液。以60 g/L葡萄糖和30 g/L木糖为碳源,分别添加上述稀酸预处理液,比较了5种预处理液对休哈塔假丝酵母(Candida shehatae)共发酵产乙醇的影响,并探究主要抑制物来源。结果表明:133 g/L全玉米秸秆稀酸预处理的降解物会完全抑制C.shehatae糖代谢和共发酵。在玉米秸秆稀酸预处理过程中,4类非木质素组分降解物均会导致乙醇得率下降,其中100 g/L纤维素降解物完全抑制木糖的发酵,半纤维素降解物同时抑制葡萄糖和木糖的发酵,甚至对酵母产生致死毒性,热水提取物和乙醇提取物降解物延滞糖利用和酵母生长。玉米秸秆共发酵产乙醇抑制物主要来自于纤维素和半纤维素在稀酸预处理中的降解反应,主要为甲酸、乙酸、乙酰丙酸、5-羟甲基糠醛和糠醛,同时还存在着其他降解产物的毒性或协同毒性。 相似文献
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速生杨二步超低酸水解液发酵制取燃料乙醇的研究 总被引：1，自引：1，他引：0
以速生杨二步超低酸水解方法获得的水解液为原料,在28℃、100 r/min等发酵条件下,选择热带假丝酵母(C.2.637)和酿酒酵母(S.2.699)分别对第一步和第二步水解液进行了发酵制取燃料乙醇的研究,并考查了Ca(OH)2中和、过中和、活性炭吸附等预处理方法及菌种预适应驯化对乙醇转化率的影响。结果表明:热带假丝酵母能够更好地利用第一步水解液生成菌体,适合生产单细胞蛋白;菌种驯化后发酵速度和乙醇转化率均有提高,尤其是以酿酒酵母发酵第二步水解液,乙醇转化率由14.45%增至39.37%;Ca(OH)2过中和的方法处理后的水解液,乙醇转化率有所增加;以五碳糖为主同时含有六碳糖的速生杨第一步水解液,假丝酵母发酵产乙醇的效果好于酿酒酵母。 相似文献
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氧对亚硫酸盐制浆废液戊糖、己糖同步酒精发酵的影响 总被引：4，自引：0，他引：4
研究了氧对休哈塔假丝酵母Ｒ的戊糖酒精发酵的影响。休哈塔假丝酵母Ｒ的戊糖酒精发酵需在“限制性供氧”条件下进行,溶解氧浓度在０９～１１ｍｇ／Ｌ时,木糖利用率和酒精得率分别为８３８％～９３５％和８８４％～９１２％;在１５Ｌ发酵罐中发酵富含戊糖的亚硫酸盐制浆废液３２ｈ,糖利用率和酒精得率分别达９２５％和８５０％,酵母细胞吸氧速率为１２４～１．４８ｍｍｏｌ／Ｌ·ｈ,溶氧系数ＫＬａ值１４７５～１８００ｈ－１;当通风量为４ｍ３／ｈ时,在５ｍ３发酵罐中发酵还原物为２２９０ｇ／Ｌ的亚硫酸盐制浆废液２２ｈ,还原物降至５９ｇ／Ｌ,醪液酒精浓度达０７４％（ｖ／ｖ）,通风量过高或过低均导致酒精得率的下降。 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