931 resultados para Sound production by animals.
A design strategy in the propulsion system attachment to a submarine hull to minimise radiated noise
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Vibration modes of a submerged hull are excited by fluctuating forces generated at the propeller and transmitted to the hull via the propeller-shafting system. The low frequency hull vibrational modes result in significant sound radiation. This work investigates the reduction of the far-field radiated sound pressure by optimising the connection point of the shafting system to the hull. The submarine hull is modelled as a fluid loaded cylindrical hull with truncated conical shells at each end. The propeller-shafting system consists of the propeller, shaft, thrust bearing and foundation, and is modelled in a modular approach using a combination of spring-mass-damper elements and continuous systems (beams, plates, shells). The foundation is attached to the stern side end plate of the hull, which is modelled as a circular plate coupled to an annular plate. By tuning the connection radius of the foundation to the end plate, the maximum radiated noise in a given frequency range can be minimised.
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An accurate description of sound propagation in a duct is important to obtain the sound power radiating from a source in both near and far fields. A technique has been developed and applied to decompose higher-order modes of sound emitted into a duct. Traditional experiments and theory based on two-sensor methods are limited to the plane-wave contribution to the sound field at low frequency. Due to the increase in independent measurements required, a computational method has been developed to simulate sensitivities of real measurements (e.g., noise) and optimize the set-up. An experimental rig has been constructed to decompose the first two modes using six independent measurements from surface, flush-mounted microphones. Experiments were initially performed using a loudspeaker as the source for validation. Subsequently, the sound emitted by a mixed-flow fan has been investigated and compared to measurements made in accordance with the internationally standardized in-duct fan measurement method. This method utilizes large anechoic terminations and a procedure involving averaging over measurements in space and time to account for the contribution from higher-order modes. The new method does not require either of these added complications and gives detail about the underlying modal content of the emitted sound.
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In order to guarantee a sustainable supply of future energy demand without compromising the environment, some actions for a substantial reduction of CO 2 emissions are nowadays deeply analysed. One of them is the improvement of the nuclear energy use. In this framework, innovative gas-cooled reactors (both thermal and fast) seem to be very attractive from the electricity production point of view and for the potential industrial use along the high temperature processes (e.g., H 2 production by steam reforming or I-S process). This work focuses on a preliminary (and conservative) evaluation of possible advantages that a symbiotic cycle (EPR-PBMR-GCFR) could entail, with special regard to the reduction of the HLW inventory and the optimization of the exploitation of the fuel resources. The comparison between the symbiotic cycle chosen and the reference one (once-through scenario, i.e., EPR-SNF directly disposed) shows a reduction of the time needed to reach a fixed reference level from ∼170000 years to ∼1550 years (comparable with typical human times and for this reason more acceptable by the public opinion). In addition, this cycle enables to have a more efficient use of resources involved: the total electric energy produced becomes equal to ∼630 TWh/year (instead of only ∼530 TWh/year using only EPR) without consuming additional raw materials. © 2009 Barbara Vezzoni et al.
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A turbulent boundary-layer flow over a rough wall generates a dipole sound field as the near-field hydrodynamic disturbances in the turbulent boundary-layer scatter into radiated sound at small surface irregularities. In this paper, phased microphone arrays are applied to the experimental study of surface roughness noise. The radiated sound from two rough plates and one smooth plate in an open jet is measured at three streamwise locations, and the beamforming source maps demonstrate the dipole directivity. Higher source strengths can be observed in the rough plates than the smooth plate, and the rough plates also enhance the trailing-edge noise. A prediction scheme in previous theoretical work is used to describe the strength of a distribution of incoherent dipoles over the rigid plate and to simulate the sound detected by the microphone array. Source maps of measurement and simulation exhibit encouraging similarities in both source pattern and source strength, which confirms the dipole nature and the predicted magnitude of roughness noise. The simulations underestimate the streamwise gradient of the source strengths and overestimate the source strengths at the highest frequency. © 2007 by Yu Liu and Ann P. Dowling.
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In this report, recombinant interieukin-8 (rIL-8) was produced and its activity tested for the first time in fish. The rainbow trout rIL-8 was produced in Escherichia coli and purified using a 6xHis tag at the N-terminus. The rIL-8 induced a dose-dependent migration of head kidney leukocytes at concentrations from 0.1 to 10 ng/ml, with a peak response at 1 ng/ml. Trout rIL-8 also had a significant effect on superoxide production by head kidney cells, with maximal, activity at 0.1 and 1 ng/ml. When injected intraperitoneally into trout, rIL-8 had a clear effect on total leukocyte number in the peritoneal cavity, with increasing doses (up to 5 mu g) eliciting more cells. Of three leukocyte types distinguished, neutrophils were the dominant cell type, especially at higher rIL-8 concentrations. In contrast, the proportion of macrophages and lymphocytes decreased with rIL-8 administration, suggesting that they were not attracted at the same rate as neutrophils. (C) 2007 Elsevier Ltd. All rights reserved.
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岷江上游地区高山/亚高山植被分布的坡向性分异显著,阴阳坡高山林线不仅物种组成差异明显,并且分布海拔呈现出阴坡高阳坡低的格局.阳坡林线树种主要是圆柏属乔木,林线类型多为渐变型,海拔高度大约在3 400m~3 800m;阴坡林线树种主要是冷杉,林线类型多为骤变型,海拔高度约在3 800m~4 400m.本研究采用土壤种子库物理筛选、室内萌发实验及野外群落调查等方法,对岷江上游地区阴坡岷江冷杉和阳坡祁连圆柏两类林线树种不同海拔梯度上土壤种子库以及幼苗库特征进行了调查,从土壤种子库和幼苗更新特征的角度对林线乔木树种种群更新特征进行了分析,进而对该地区高山林线在阴阳坡分布差异的原因进行了探讨,结果显示: 1.土壤种子库 阴坡:阴坡高山林线附近岷江冷杉土壤种子的平均密度大约为50.96粒/m2,其中树线以上10m处土壤种子密度为1.00粒/m2,树线处大约19.33粒/m2,林线交错带内土壤种子密度最高为136.83粒/m2,郁闭林内种子密度小于林线交错带,只有30.50粒/m2,种子平均空壳率为52%,霉变率达34%,完好种子只有6%.土壤种子库垂直分布特征为地被物层含种子比重最大,大约在67.50%左右;其次为0~2cm层,约18.84%左右;2~5cm层所占种子比例最小,约13.66%左右.霉变种子数量与土壤深度呈负相关. 阳坡:阳坡祁连圆柏土壤种子的平均密度为60.16粒/m2.树线以上10m处密度为1.92粒/m2,树线位置大约108.16粒/m2,林线交错带内平均为75.80粒/m2,郁闭林内种子密度小于林线交错带,只有20.00粒/m2.种子平均空壳率为36%,完好种子占49%,霉变率较低,大约为10%.阴阳坡林线树种土壤种子库垂直分布特征为:地被物层含种子最多,其次为0~4cm层,4~10cm层所占种子比例最小,霉变种子数量与土壤深度也呈负相关. 2. 幼苗库调查 阳坡:在树线以上区域没有发现幼苗,林线交错带内幼苗密度平均达3 250株/hm2,郁闭林内仅2 750株/ hm2.整个样地内1~2a幼苗很少甚至没有出现,3~10a的幼苗相对较多.空间分布上,祁连圆柏幼苗在林线交错带内接近随机分布,郁闭林内则介于随机分布和均匀分布之间. 阴坡:在树线以上幼苗密度为1 250株/ hm2,全部为1~2a幼苗,林线交错带内幼苗密度平均达7 000株/ hm2,郁闭林内达6 250株/ hm2.林线附近岷江冷杉幼苗丰富度以及幼苗的出现频率明显高于祁连圆柏,年龄结构也较祁连圆柏完整.岷江冷杉幼苗空间分布除了树线处幼苗的分布为随机分布,其他海拔则为集群分布. 3.从不同土壤深度的种子总量和幼苗数量的相关性检验发现,当年生幼苗数量跟表层种子总量相关性极显著, 但是两年生幼苗的数量与底层种子数量相关性显著.土壤种子在土壤中的垂直分布格局从一定程度上可以反映种子库的年际特征.岷江冷杉土壤种子库较丰富,种子散布后的存活力随着时间的变化逐渐下降,属于季节性瞬时种子库;祁连圆柏土壤种子散布格局为集群型分布,成熟种子大部分散布在母株冠幅内,属于永久性土壤种子库. 4.在阴坡林线交错带及以上区域还存在较为丰富的乔木土壤种子,并且在树线以上区域还发现了少量的岷江冷杉幼苗.从样地乔木的年龄结构发现,在林线交错带内上部到树线位置主要以幼龄林为主,且年龄结构完整,基本符合入侵性林线特征;阳坡林线交错带内幼苗出现频率很低,树线以上区域虽然存在种子库,但是没有幼苗出现,在林线交错带内乔木径级差距很大,年龄结构异常不完整,这种特征的林线将会面临两个可能结果:一种是维持现有状态,保持平衡;另外一种就是退化,但阳坡林线的实际动态趋势还有待长期定点研究. Treelines on the upper region of Minjiang River differ between the north aspect and the south aspect in their appearances, altitudes and tree species. On the north aspect, trees of Abies form a sharp and abrupt treeline ranging from 3800m to 4400m, while on the south the treeline is generally lower(3 400~3 800m), more open and gradual and mostly composed of Sabina. In this study, we examined the altitudinal gradients of soil seed banks and seedling recruitments at the treeline ecotones of a N-aspect and a S-aspect by using soil sieving, germination experiment and field investigations, analyzed the characteristics of population regeneration of tree species at the transitional zone and presented a analysis of the causes to the aspect-related difference in treeline patterns in the study area. Major results of our study include: 1. Soil seed bank N-aspect: Of the 50 plots investigated, the average density of soil seeds is 50.96/m2, in which well-formed seeds account for 6%, empty seeds 52%, parasitized seeds34%, and seeds damaged by animals 8%. The size of soil seed bank varies along altitude, being 1.00 seeds /m2 at the 10m above the treeline and ca.19.33 seeds/m2 at the upper limit of treeline. The highest density (136.83 seeds/m2) occurs at the treeline ecotone. By contrast, the density of soil seed for the closed forest is only 30.50 seeds/m2. In terms of vertical strata, 67.50% of the total seeds are at the surface layer, 18.84% at the middle layer (0~2cm) and 13.66% at deeper layer (2~5cm). The number of parasitized seeds is negatively correlated to soil depth. S-aspect: Of the 50 plots investigated, the average density of soil seeds is 60.16 seeds/m2, and the well-formed seeds account for 49%, empty seeds 36%, parasitized seeds10%, and seeds damaged by animals 1%. The size of soil seed bank varies along altitude, with 1.92 seeds/m2 recorded at the10m above the treeline,108.16 seeds/m2 at the upper limit of treeline, and 75.80 seeds/m2 at the treeline ecotone, while that for the closed forest is 20.00 seeds/m2. The number of seeds decreases with the depth of soil. As is on the N-aspect, the size of soil bank, from large to small, follows the order of the surface layer, the middle layer (0~4cm) and the bottom layer (4~10cm). The number of parasitized seeds is also negatively correlated to the depth of the soil. 2. Seedling bank N-aspect: A mean maximum seedling abundance of 31 000 seedlings/hm2 was recorded near alpine treeline at growing season. The density of seedlings is 1 250 seedlings/ha (all being 1 or 2 years old) at the alpine meadow 10m away above treeline, 7 000 seedlings/ha at treeline ecotone and 6 250 seedlings/ha for closed forest.The spatial distribution of Abies faxoniana seedlings is random at the upper limit of the treeline but clumped at other altitudes. S-aspect: No seedlings were found at the alpine meadow 10m away from the treeline. The density of seedlings was 3 250 seedlings/ha at treeline ecotone and 2 750 seedlings/ha for the closed forest.Hardly any 1 year current and 2 year-old seedlings appeared at the plots. The spatial distribution of Sabina przewalskii seedlings is random at treeline ecotone and between “random” and “even” forest closed forest. 3.Correlation tests of seedling population and seed bank at different soil layers indicated that the emergents were strongly correlated to seed bank at surface layer while the number of two-year seedlings was significantly correlated to the seed bank at the bottom of soil layer, indicating that germination mainly occurs at the soil surface while the middle or bottom layer was the reserve for non-germination or dead seeds. It can thus be postulated that Abies faxoniana soil seed bank is of seasonal transient type. By contrast, the soil seed bank of Sabina przewalskii is of persistent type and the soil seeds and seedlings of this species occurred more frequently near the islands of adult trees. 4.A good many soil seeds of both tree species were found near the treeline ecotone and above at N- and S-aspects. A few young seedlings were found above the Abies treeline. Investigation of five altitudinal transects respectively on N- and S-aspects indicated that Abies faxoniana has a more complete age structure than the stands of Sabina przewalskii. The age of firs decreased from closed forest to the upper limit of treeline, which suggests that the Abies treeline is advancing to higher altitude. While on the south aspect, only few Sabina przewalskii soil seeds and nearly no seedlings were found above the treeline ecotone. The stands exhibit extremely great difference in diameter classes with significantly incomplete age structure. This would lead to two possible results for the treelines: maintaining an equilibrium state at the current position or degenerating. But more studies should be carried out at longer time scales or larger spatial scales to understand whether the Sabina treeline is degenerating.
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本文结合我国燃料乙醇发展的方针政策,以酿酒酵母和运动发酵单胞菌为菌种研究其在非粮能源作物木薯中乙醇发酵的情况,为木薯原料更好地应用于生产中提供了理论依据。 酿酒酵母木薯高浓度乙醇发酵的研究。实验采用的木薯干淀粉含量约70-75%。以酿酒酵母为菌种进行高浓度乙醇发酵的工艺条件研究,最佳条件为:木薯干粉碎细度为35目,料水比1:2,α-淀粉酶用量0.09 KNU/g淀粉,蒸煮温度85 ℃,蒸煮时间15 min。采用30 ℃同步糖化发酵工艺,糖化酶用量为3.4 AGU/g淀粉,发酵时间30 h。在10 L发酵罐中,乙醇质量比达127.88 g/kg,发酵效率为88.28%,发酵强度4.263 g/kg/h,100 L中试研究中乙醇浓度为127.75 g/kg,发酵强度4.258 g/kg/h。利用高效液相色谱对发酵液中残糖进行了分析,证明葡萄糖、果糖等单糖已完全被菌体利用,剩余糖为二糖,三糖等不可发酵的低聚糖。 运动发酵单胞菌快速乙醇发酵的研究。对实验室保藏的8株运动发酵单胞菌进行比较,选择发酵速度最快的Zymomonas mobilis232B进行研究。该菌在纯葡萄糖中的最佳发酵条件为:葡萄糖浓度18%,起始pH 6-7,发酵温度30 ℃,发酵时间18 h,乙醇浓度88 g/kg。在以木薯为底物同步糖化快速乙醇发酵中,采用Full Factorial设计和最速上升实验确定了培养基成分中的2个显著性因子及其最适浓度:酵母粉4 g/kg,硫酸铵0.8 g/kg。在最适培养基条件下,对木薯料水比和糖化酶用量进行了优化,得到Z.mobilis232B木薯乙醇发酵最佳料水比1:3,糖化酶浓度4 AGU/g淀粉,乙醇发酵4.915 g/kg/h。利用高效液相色谱对发酵液中残糖进行了分析,剩余糖为二糖,三糖等,但成分较酵母发酵后复杂。 According to the fuel ethanol development plans and policies in our country, the ethanol production from cassava by Saccharomyces cerevisiae and Zymomonas mobilis was studied. It provided theoretical basis for ethanol fermentation by cassava in industry. Part 1 is the study of VHG (very high gravity) ethanol fermentation by Saccharomyces cerevisiae. The content of starch in cassava was 70-75%. Compared with the performances under different experimental conditions, the following optimal conditions for VHG fermentation were obtained: Granule size of dry cassava 35 mashes, hydromodulus of cassava to water at 1:2, α-amylase enzyme dosage 0.09 KNU/g starch, cooking temperature 85 ℃ for 15 min, using the SSF process (simultaneous saccharification and fermentation) and the amount of glucoamylase 3.4 AGU/g starch. Accordingly, the final ethanol concentration was up to 127.88 g/kg; the ethanol yield reached 88.28%, and ethanol productivity was 4.263 g/kg/h after 30 h. When the fermentation scale expanded to 100 L, the final ethanol concentration was 127.75 g/kg, and the ethanol productivity was 4.258 g/kg/h in 30 h. The residual sugar was analyzed by high performance liquid chromatography, and proved that there was no glucose and fructose. The residual reducing sugar was some unfermentable oligosaccharide Part 2 is the study of the rapid ethanol production by Zymomonas mobilis. Compare with other seven stains, Zymomonas mobilis 232B was selected for research. The optimum condition in glucose medium was as follow: glucose concentration 18%, initial pH 6-7, and fermentation temperature 30 ℃. The ethanol concentration was 88g/kg in 18 h. After that, rapid ethanol production from cassava in SSF by Zymomonas mobilis 232B was studied. Through a series of experiments aided by Full Factorial Design and steepest ascent search, the optimal concentration yeast extract and ammonium sulfate were determined: 4 g/kg and 0.8 g/kg, each. Under optimum medium conditions, the optimal hydromodulus of cassava to water and glucoamylase dosages were obtained: hydromodulus of cassava to water at 1:3 and glucoamylase dosages 4 AGU/g starch. The ethanol production reached 4.915 g/kg/h. The residual sugar was analyzed by HPLC, and proved that the residual reducing sugar was some unfermentable oligosaccharide,but the components were more complex than that fermentation by Saccharomyces cerevisiae.
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本文从新鲜大熊猫粪便和实验室保存的沼气发酵富集物中筛选得到 4 株厌氧纤维素分解菌B5、C3、D3-2、D4-1,利用这4 株菌预处理秸秆,然后将预处理后的秸秆用本实验室保存的厌氧产氢菌来发酵进行生物产氢。同时还比较研究了:○1 用1% H2SO4、25% NH3 · H2O和12% NaOH对秸秆进行化学预处理;○2 用厌氧纤维素分解菌对秸秆进行生物预处理;○3 化学与生物组合预处理对秸秆发酵生物产氢的影响。实验结果表明:12% NaOH和生物组合预处理后的秸秆发酵产氢效果最好,其产氢量为21.04 mL g-1,是未经预处理秸秆的75 倍;最高氢气浓度为57.3%,是未经预处理秸秆的96 倍;其产氢的最适pH 为4.5 ~ 6.0,最佳底物浓度为45 ~ 55 g L-1;其发酵过程中的挥发性脂肪酸(VFAs)以乙酸和丁酸为主。 本实验筛选到的 4 株厌氧纤维素分解菌株中,B5 和D4-1 在降解纤维素的同时还具有直接以纤维素为底物产氢的功能,因此本文分别对菌株B5 和D4-1 以及二者的组合菌株B5+D4-1 直接利用秸秆为基质发酵生物产氢做了初步探索研究。结果发现:组合菌株发酵产氢的效果以及对秸秆纤维素和半纤维素的降解率要比单菌株好。菌株B5+D4-1 发酵,秸秆的产氢量为11.4 mL g-1,分别是B5 和D4-1 单菌株的1.6 倍和3.1 倍;组合菌株B5+D4-1 发酵的最大氢气浓度为31.6%,分别是B5 和D4-1 单菌株的1.3 倍和2.4 倍。在发酵过程中,组合菌株B5+D4-1 对秸秆纤维素和半纤维素的最高降解率分别为35.0%和11.8%,分别是菌株B5 的1.2 倍和1.1 倍,是菌株D4-1的1.5 倍和1.3 倍。菌株B5,D4-1 以及组合菌株B5+D4-1 发酵过程产生的挥发性脂肪酸(VFAs)均以乙酸为主。菌株B5 单独发酵过程中只检测到乙酸和丁酸,菌株D4-1 单独发酵以及组合菌株B5+D4-1 发酵过程检测到有乙醇、乙酸和丁酸。 The fermentative bio-hydrogen production by anaerobic hydrogen bacteria preserved in our laboratory from the straw which had been pretreated by four anaerobic cellulolytic decomposition strains of B5, C3, D3-2, D4-1 which were isolated and screened from giant panda’s excrement and biogas fermentation enrichments conserved in our laboratory was studied. Besides, the impact of chemical(1% H2SO4、25% NH3·H2O and 12% NaOH), biological (cellulolytic strains of B5, C3, D3-2, D4-1) and chemical-biological combination pretreatment on bio-hydrogen production from straw by fermentation was also comparatively studied. The experiments showed that the best results of bio-hydrogen production were obtained from the straw with 12% NaOH-biological combination pretreatment method, its capability of bio-hydrogen production was 21.04 mL g-1, which was 75 times higher than the straw without pretreatment; the maximum concentration of H2 was 57.3%, which was 96 times higher than the straw without pretreatment; its optimum pH range was 4.5 ~ 6.0, and its optimum range of substrate concentration was 45 ~ 55 g L-1; In the process of fermentation, the main composition of VFAs were acetate and butyrate. Among the four strains of B5, C3, D3-2, D4-1, B5 and D4-1 have the function of hydrogen-producing by cellulose used as substrate when it decompose cellulose, so the preliminary exploration and research on fermentative bio-hydrogen production by B5, D4-1 and B5+D4-1 which directly used straw as substrate was carried out. The results showed that the combination strains of B5+D4-1 was strikingly better than either B5 or D4-1 strain in the fermentative hydrogen production. The hydrogen-production capability of B5+D4-1 was 11.4 mL g-1 which was respectively 1.6 times and 3.1times higher than B5 and D4-1; the maximum hydrogen concentration of B5+D4-1 was 31.6% which was respectively 1.3 times and 2.4 times higher than B5 and D4-1. In the process of fermentation, the maximum degradation rate of cellulose and hemicellulose in straw was respectively 35.0% and 11.8% by B5+D4-1, which was 1.2 times and 1.1 times higher than B5, and was 1.5 times and 1.3 times higher than D4-1 respectively. The Volatile Fattty Acids(VFAs) generated in the process of fermentation with strains of B5, D4-1 and B5+D4-1 were all mainly acetate. Acetate and butyrate were detected in the process of fermentation with B5, ethonal, acetate and butyrate were detected in the process of fermentation with D4-1 and B5+D4-1.
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生物质燃料乙醇是一种高度清洁的交通液体燃料,是减少温室气体排放,缓解大气污染的最佳技术选择。以非粮原料生产燃料乙醇可以在进行能源生产的同时保证粮食安全,有利于产业的可持续发展。在众多的非粮原料中,甘薯是我国开发潜力最大的生物质能源作物之一。我国占世界甘薯种植总面积和产量的90%。同时,甘薯的单位面积燃料乙醇产量远大于玉米和小麦。其成本是目前酒精中最低廉的,因此利用甘薯生产乙醇是发展生物质燃料乙醇的首要选择。目前采用薯类全原料主要采用分批发酵生产乙醇,其技术水平低,发酵强度低,一般在0.7-2.5g/(L•h),乙醇浓度低,甘薯发酵乙醇为6-8%(v/v),能耗高,环境负荷大,污染严重。针对上述问题,本文从菌株选育、原料预处理、中试放大、残糖成分分析等方面进行研究。 为了研究乙醇发酵生产规模扩大过程中,大型发酵罐底部高压条件下,CO2对酵母乙醇发酵的影响,我们通过CO2 加压的方法进行模拟试验,研究结果表明,发酵时间随压强的升高而逐渐延长,高压CO2 对乙醇发酵效率影响不大,在0.3 MPa 以下时,发酵效率均可达到90%以上。高压CO2 对发酵的抑制作用是高压和CO2 这两个因素联合作用的结果。高压CO2 条件下,酵母胞外酶和胞内重要酶类的酶活均表现出特征性。0.2 MPa 下,酶活性的变化趋势和0.1 MPa 条件下的较为一致。而0.3 MPa 下的酶活变化趋势与0.4 MPa 下的酶活更为接近。通过全基因表达分析发现在CO2 压力为0.3 MPa 下,乙醇发酵途径中多个基因表达量下调,同时海藻糖合成酶和热激蛋白基因表达量上调。 筛选耐高温的乙醇酵母菌株能够解决糖化温度和发酵温度不协调的矛盾,实现真正意义上的边糖化边发酵。高温发酵还能够降低发酵时的冷却成本,实现乙醇的周年生产。本研究筛选出一株高温发酵菌株Y-H1,进而我们对该菌株的胞外酶和胞内乙醇代谢重要酶类的酶活性进行了分析。结果表明Y-H1 能够在40 ℃条件下正常进行乙醇发酵,发酵33h,最终乙醇浓度达到10.7%(w/w),发酵效率达到90%以上。同时发酵液最终pH 在3.5 左右,显示菌株具有一定的耐酸性能力。同时观察到40 ℃下,菌株的胞外酶和胞内乙醇代谢重要酶类的酶活性发生了变化,乙醇发酵途径中关键酶基因表达下调,而海藻糖合成酶与热激蛋白基因表达量上调,这些结果为进一步研究酵母菌耐热调控机理提供了依据。 糖蜜是一种大规模工业生产乙醇的理想原料,本研究利用选育高浓度乙醇发酵菌株结合配套的发酵稳定剂,研究了糖蜜高浓度乙醇发酵情况。结果表明采用冷酸沉淀预处理糖蜜溶液,采用分批补料的发酵方式,乙醇浓度最高达到了10.26% (w/w),发酵时间为42 h。同时观察到在糖蜜发酵中,乙醛含量与乙醇浓度存在一定的相关性。 快速乙醇发酵对于缩短乙醇生产周期、降低乙醇生产成本、减少原料腐烂损失具有重要意义。本研究诱变和筛选得到了一株快速乙醇发酵菌株10232B。在优化后的发酵条件下,采用10L 发酵罐进行分批乙醇发酵,经过18h,乙醇的最终浓度达到88.5g/L,发酵效率93.6%,平均乙醇生产速度达到4.92 g/L/h。此菌株在保持较高乙醇生产浓度的同时,拥有快速生产乙醇的能力,适合作为快速乙醇发酵生产菌种。 由于鲜甘薯具有粘度大的特点,传统液化糖化处理很难在短时间内充分糖化原料;高粘度的醪液也难以进行管道输送,容易堵塞管路;同时,也会降低后续的乙醇发酵效率。 本文采用了快速粘度分析法对鲜甘薯糊化粘度特性进行了分析,进而对预处理条件进行了研究,在最佳预处理条件下,糖化2h 后,醪液葡萄糖值最高可达99.3,粘度4.5×104 mPa.s,而采用传统糖化工艺,醪液DE 值仅为85.8,粘度大于1.0×105 mPa.s。 此预处理方法也可用于快速糖化不加水的醪液。后续的乙醇发酵试验表明,通过此预处理方法获得的糖化醪液对乙醇发酵无负面影响。 在前期已实现了实验室水平的鲜甘薯燃料乙醇快速乙醇发酵基础上,进一步将发酵规模扩大到500L,在中试水平上对甘薯乙醇发酵进行了研究。结果表明在500L 中试规模,采用边糖化边发酵(SSF)工艺,在料液比为3∶1,发酵醪液最高粘度为6×104mPa.s 条件下,发酵37h,乙醇浓度达到了12.7%(v/v),发酵效率91%,发酵强度为2.7 g/(L•h)。与目前国内的薯类乙醇发酵生产技术水平具有明显的优越性。 为研究甘薯、木薯乙醇发酵中残糖的组成,采用了高效液相色谱—蒸发光散射检测法,对乙醇发酵残糖进行了分析。结果表明,甘薯、木薯乙醇发酵残糖均为寡聚糖,主要由葡萄糖、木糖、半乳糖、阿拉伯糖和甘露糖构成。随着发酵时间延长,寡聚糖中的葡萄糖、半乳糖、甘露糖可被缓慢的水解释放。提高糖化酶量仅在一定程度上降低残糖,过量的糖化酶反而会导致残糖增加。同时发现3, 5-二硝基水杨酸法不能准确测定甘薯、木薯乙醇发酵中的残总糖含量。进一步筛选了两株残糖降解菌株,对甘薯乙醇发酵残糖的降解利用率均达到了40%以上,而且还能显著降低发酵醪液粘度。经形态学和rRNA ITS 序列分析,确定这两株菌分别属于为木霉属和曲霉属黑曲霉组。 通过对以甘薯原料为代表的非粮原料发酵技术研究开发,以期形成乙醇转化率高,能耗低,生产效率高、季节适应性好,原料适应性广,经济性强,符合清洁生产机制的燃料乙醇高效转化技术,为具有我国特色的燃料乙醇发展模式提供技术支持。 Sweet potato is one of the major feedstock for the fuel ethanol production in China. The planting area and the yield in China take 90% of the world. Sweet potato is an efficient kind of energy crops. The energy outcome per area is higher than corn or wheat. And the manufacture cost of ethanol is the lowest, compared with corn and wheat. So sweet potato is the favorable crop for the bioethanol production in China. However, the low-level fermentation technology restricts the development of ethanol production by sweet potato, including slow ethanol production rate, low ethanol concentration and high energy cost. To solve these problems, we conducted research on the strain breeding, pretreatment, pilot fermentation test and residual saccharides analysis. To study the impact of hyperbaric condition at bottom of the large fermentor on yeast fermentation, high pressure carbon dioxide (CO2) was adopted to simulate the situation. The results showed that the fermentation was prolonged with the increasing pressure. The pressure of CO2 had little impact on the ethanol yield which could reach 90% under the pressure below 0.3 MPa. The inhibition was combined by the high pressure and CO2. Under the high CO2 pressure, the extracellular and important intracellular enzyme activities were different from those under normal state. The changes under 0.1 MPa and 0.2 MPa were similar. The changes under 0.3 MPa were closer to those under 0.4 MPa. The application of thermotolerance yeast could solve the problem of the inconsistent temperature between fermentation and saccharificaton and fulfill the real simultaneous saccharification and fermentation. And it could reduce the cooling cost. A thermotolerance strain Y-H1 was isolated in our research. It gave high ethanol concentration of 10.7%(w/w)at 40 ℃ for 33 h. The ethanol yield efficiency was over 90%. At 40 ℃, the extracellular and important intracellular enzyme activities of Y-H1 showed the difference with normal state, which may indicate its physiological changes at the high temperature. Molasses is another feedstock for industrial ethanol production. By our ethanol-tolerance strain and the regulation reagents, the fermentation with high ethanol concentration was investigated. In fed-batch mode combined with cold acid deposition, the highest ethanol concentration was 10.26% (w/w) for 42h. The aldehyde concentration in fermentation was found to be related to ethanol concentration. The development of a rapid ethanol fermentation strain of Zymomonas mobilis is essential for reducing the cost of ethanol production and for the timely utilization of fresh material that is easily decayed in the Chinese bioethanol industry. A mutant Z. mobilis strain, 10232B, was generated by UV mutagenesis. Under these optimized conditions, fermentation of the mutant Z. mobilis 10232B strain was completed in just 18 h with a high ethanol production rate, at an average of 4.92 gL-1h-1 per batch. The final maximum ethanol concentration was 88.5 gL-1, with an ethanol yield efficiency of 93.6%. This result illustrated the potential use of the mutant Z. mobilis 10232B strain in rapid ethanol fermentation in order to help reduce the cost of industrial ethanol production. As fresh sweet potato syrup shows high viscosity, it is hard to be fully converted to glucose by enzymes in the traditional saccharification process. The high-viscosity syrup is difficult to be transmitted in pipes, which may be easily blocked. Meanwhile it could also reduce the later ethanol fermentation efficiency. To solve these problems, effects of the pretreatment conditions were investigated. The highest dextrose equivalent value of 99.3 and the lowest viscosity of 4.5×104 mPa.s were obtained by the most favorable pretreatment conditions, while those of 85.8 and over 1.0×105 mPa.s was produced by traditional treatment conditions. The pretreatment could also be applied on the material syrup without adding water. The later experiments showed that the pretreated syrup had no negative effect on the ethanol fermentation and exhibited lower viscosity. The fuel ethanol rapid production from fresh sweet potato was enlarged in the 500L pilot scale after its fulfillment on the laboratory level. The optimal ratio of material to water was 3 to 1 in 500L fermentor. With low-temperature-cooking (85 ℃) using SSF, the Saccharomyces cerevisiae was able to produce ethanol 97.44 g/kg for 37h, which reached 92% of theoretical yield. The average ethanol production rate was 4.06 g/kg/h. And the maximum viscosity of syrup reached 6×104mPa.s. The results showed its superiority over current industrial ethanol fermentation. The compositions of the residual saccharides in the ethanol fermentation by sweet potato and cassava were analyzed by high performance liquid chromatography coupled with evaporative light-scattering detector. The results showed that all the residual saccharides were oligosaccharides, mainly composed of glucose, xylose, galactose, arabinose and mannose. The glucose, galactose and mannose could be slowly hydrolyzed from oligosaccharides in syrup during a long period. To increase the glucoamylase dosage could lower the residual saccharides to a certain extent. However, excess glucoamylase dosage led to more residual saccharides. And the method of 3, 5-dinitrosalicylic acid could not accurately quantify the residual total saccharides content. Two residual saccharides degrading strains were isolated, which could utilize 40% of total residual saccharide and lower the syrup viscosity. With the analysis of morphology and internal transcribed spacer sequence, they were finally identified as species of Trichoderma and Aspergillus niger.
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本文筛选出一株能利用木糖产乙醇的丝状真菌Z7,对其利用木糖和半纤维素水解产物产乙醇的发酵条件进行了研究,并对Z7 利用玉米芯产木聚糖酶的条件进行了优化。全文分为三部分: 第一部分:目标微生物筛选、纯化及系统发育分析。以木糖为唯一碳源,采用梯度稀释和平板化线法从高温、中温酒曲中分离到16 株能利用木糖良好生长的丝状真菌;通过发酵试验复筛,获得一株能产乙醇的丝状真菌Z7;综合形态学和ITS 序列分析,初步鉴定为Aspergillus flavus。 第二部分:Z7 的乙醇发酵条件研究。以木糖为碳源,通过单因素试验确定最佳氮源和发酵温度;通过正交试验及SPSS 软件分析得到了不同N、P、K 成分对乙醇、残糖和菌体干重的影响。获得最佳的发酵条件为:(g/L)木糖50,尿素1, NH4NO3 1, K2HPO4 2 , KCl 0.5 , MgSO4.7H2O 0.5 , NaNO3 1 , pH 自然,培养温度33 ℃。以玉米芯半纤维素稀酸水解液为底物进行乙醇发酵,根据稀酸水解的单糖释放量和乙醇产量,确定115 ℃,1 h 为最佳玉米芯预处理条件;结合最佳发酵条件,添加1 g/L 的吐温20 能获得最大的乙醇浓度8.31 g/L。因此,Aspergillus flavus Z7 能利用半纤维素水解产物产乙醇,其中木糖的利用率80%以上。 第三部分:Z7 利用玉米芯产木聚糖酶条件优化。Aspergillus flavus Z7 在具有产乙醇能力的同时还具有产木聚糖酶的能力。本文通过单因素和正交试验得到最佳产酶培养基组分为:(g/L)玉米芯20,尿素2, 酵母膏2.5, K2HPO4 5,NaNO31, MgSO4.7H2O 1。单因素试验表明,用纱布代替塑料布密封摇瓶封口能显著提高产酶量;Z7 在碱性条件下具有更强的产酶性能。在最优条件下发酵,能产生最大木聚糖酶活122.23IU/mL。通过薄层分析,验证了Z7 产生的木聚糖酶具有水解木聚糖生成木糖及木寡糖的能力。 A strain of filamentous fungus which can produce ethanol by using the xylose was isolated in this research. The ethanol fermention conditions from xylose and dilute-acid hydrolyzate of the corn core were studied. The conditions of xylanase production by Z7 were also optimized. The paper involved three parts. Part1: Isolation, purification and phylogenetic analysis of the microbe. By using xylose as the single carbon source and the pla te streaking method, several filamentous fungi were isolated from the wine starter; through the fermentation test, a filamentous fungus Z7 which can produce ethanol was further recognized; furthermore, according to the morphologic observation and ITS seque nces analysis, Z7 was identified as Aspergillus flavus at the first step. Part2: Research on the condition of ethanol fermentation by Z7. By single factor experiment, the optional nitrogen resource and temperature of the fermentation were fixed; meanwhile, through the orthogonal array tests and the analysis of statistic software SPSS, the optional component of the culture medium and the fermentation condition were organized as follows: (g/L) xylose 50, urea 1, NH4NO3 1, K2HPO4 2, KCl 0.5 , MgSO4.7H2O 0.5, NaNO31, pH nature, temperature 33℃. Based on these optimal parameters, the fermentation of dilute-acid hydrolyzate of the corn core was carried on by Z7. According to the quantities of released sugar monomers and content of the ethanol, 115℃ in 1h is the best pretreatment condition; the maximal ethanol content can be obtained when 1g/L Tween 20 was added to. Therefore, the filamentous fungus Aspergillus flavus can use the hydrolysate of hemicellulose to produce ethanol, and the rate of xylose utilization was over 80%. Part3: Optimization of Z7’s xylanase producing condition from corn core. Aspergillus flavus Z7, which can utilize xylose or the hydrolysate of hemicellulose to produce ethanol, also had the ability of xylanase production. The optional component of the culture medium were fixed by the single factor experiment and the orthogonal array tests, and they were organized as follows: (g/L) corn core 20, Urea 2, Yeast extract 2.5, K2HPO4 5, NaNO31, MgSO4.7H2O 1; it was testified by the single factor experiment that sealing the shaking flasks with pledget other than plastic paper can obviously increase the xylanase activity; moreover, Z7 showed better xylanase production ability when in the alkali environment. Under the optional fermentation condition, the maximal xylanase activity 122.23IU/mL was proved. Through the analysis of thin- layer chromatography (TLC), the ability of xylanase from Z7, which can hydrolyze xylan to xylose monomer and oligomer, was vividly displayed.
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Plant cell cultures have been suggested as a feasible technology for the production of a myriad of plant-derived metabolites. However, commercial application of plant cell culture has met limited success with only a handful of metabolites produced at the pilot- and commercial-scales. To improve the production of secondary metabolites in plant cell cultures, efforts have been devoted predominantly to the optimization of biosynthetic pathways by both process and genetic engineering approaches. Given that secondary metabolism includes-the synthesis. metabolism and catabolism of endogenous compounds by the specialized proteins, this review intends to draw attention to the manipulation and optimization of post-biosynthetic events that follow the formation of core metabolite structures in biosynthetic pathways. These post-biosynthetic events-the chemical and enzymatic modifications, transport, storage/secretion and catabolism/degradation have been largely unexplored in the past. Potential areas are identified where further research is needed to answer fundamental questions that have implications for advanced bioprocess design. Anthocyanin production by plant cell cultures is used as a case study for this discussion, as it presents a good example of compounds for which there are extensive research publications but still no commercial bioprocess. It is perceived that research on post-biosynthetic processes may lead to future opportunities for significant advances in commercial plant cell cultures. (C) 2002 Elsevier Science Inc. All rights reserved.
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中国科学院山西煤炭化学研究所