共查询到20条相似文献,搜索用时 31 毫秒
1.
This study describes the results of a hollow fibre membrane reactor with immobilized treated cells of Zymomonas mobilis which produced sorbitol and gluconic acid continuously from fructose and glucose respectively. A productivity of 10–20 g sorbitol · L -1 · h -1 and 10–20 gluconate · L -1 · h -1 (based on total bioreactor volume) from a feed of 100 g · L -1 each of glucose and fructose was possible at high dilution rates. Kinetic parameters describing the reaction rate of treated cells in batch reactors were used to analyse the performance of the hollow fibre membrane reactor employing significant convective mass transfer. No significant mass transfer limitation was apparent. 相似文献
2.
Cyclodextrin glycosyl transferase (E.C: 2.4.1.19) from Bacillus, macerans and from a Bacillus sp. isolate was immobilized by two methods, viz. to epoxy-activated Sepharose and to alkylamine silica treated with glutaraldehyde. Because of the ready availability, low cost ($0.01/g), good surface area (30 M 2/g) and ease of operation of a continuous cylindrical reactor, the high silica fabric was chosen. The immobilized enzyme had a pH optimum shifted to the alkaline side (from 6.5 to 7.5) and had a reduced temperature optimum (from 60°C to 50-55°C). Reuse efficiency showed 65% reduction in the overall activity of the immobilized enzyme after 10 cycles of 48 h each. Continuous operation at 55°C of a cylindrical reactor of 141 ml capacity, using the immobilized enzyme (80 g of high - silica fabric containing 114 mg of purified enzyme) gave a maximum productivity of 10.2 g of cyclodextrins L -1 h, -1, at a dilution rate of 0.32 h -1 and a substrate concentration of 20 g L -1. The half life of the biocatalyst was found to be 22 days, which could be further improved by using a lower operating temperature. Over the useful life time of the immobilized biocatalyst (22 days), the total Cyclodextrin produced was of the order of 88 Kg. 相似文献
3.
The bacterium Serratia entomophila (Enterobacteriaceae) has been developed as a commercially available biopesticide for control of the pasture pest Costelytra zealandica. The influence of culture medium composition, dissolved oxygen (DO) concentration and harvesting time were investigated in order to optimise the production of S. entomophila. In batch fermentations, highest yields were achieved using sucrose (40 g L -1) as the carbon source, followed closely by fructose and molasses. The effect of yeast extract (YE), marmite and bakery yeast as cell growth enhancers was also examined in both batch and fed-batch mode. Culture medium containing 20 g L -1 of YE (fed-batch) produced the highest cell density. No significant effect on cell yield was detected when cultures were supplemented with bakery yeast or marmite. The DO concentration influenced biomass production: a 5-fold increase in cell density was achieved when the concentration of DO was maintained in the range of 20-50% (5.7×10 10 CFUs mL -1) in comparison with 1% (1.2×10 10 CFUs mL -1). In cultures maintained at 1 and 20% DO concentration, cells harvested from the exponential growth phase survived for less than 2 weeks when stored at 4°C. In contrast, high cell survival (85-100%) was achieved when cells were harvested after they had entered the stationary growth phase. Recommendations are provided for the production of robust, high cell density cultures of S. entomophila. 相似文献
4.
Continuous asymmetric reduction of 4-oxoisophorone by the thermophilic bacterium Thermomonospora curvata JTS321 was examined using three reactor systems: packed bed, fluidized bed and hollow fiber. T. curvata was immobilized in polyacrylamide-hydrazide gels when used in the packed and fluidized bed reactors. Of the three reactor systems, the highest productivity (964 mg.1 -1.h -1) was observed in the fluidized bed reactor. However, many cells grew outside of the gel matrix, causing product contamination. The productivity of the hollow fiber reactor was 504 mg.1 -1.h -1; the problem of cell contamination of the product was avoided, as the molecular cut-off of the hollow fibers (400 000) was of an appropriate size to prevent cell leakage to the product stream. We therefore consider that the hollow fiber reactor is most suitable for continuous microbial conversions. 相似文献
5.
In 1984, an underground storage tank leaked approximately 41,000 L of gasoline into the ground water at the Naval Construction Battalion Command in Port Hueneme, CA (USA). Benzene, toluene, ethylbenzene, and xylenes (BTEX) contamination stimulated remedial action. In 1995, a ground water circulation well (GCW) and network of surrounding monitoring wells were installed. After year of operation, dissolved oxygen and nitrate concentrations remained low in all monitoring wells. Benzene utilization (the sum of respiration, uptake, and conversion to polar compounds) ranged from 0.03 to 4.6 µg L -1 h -1, and toluene utilization ranged from 0.01 to 5.2 µg L -1 h -1. Heterotrophic bacterial productivity (total carbon assimilation) increased dramatically in the GCW, although benzene and toluene utilization decreased markedly relative to surrounding wells. Benzene and toluene uptake accounted for a significant proportion (mean=22%) of the heterotrophic bacterial productivity except within the GCW, indicating other fuel contaminant or indigenous organic carbon and not BTEX compounds served as primary carbon source. The GCW effectively air-stripped BTEX compounds, but failed to stimulate benzene and toluene biodegradation and thus would not be effective for stimulating BTEX bioremediation under current deployment parameters. Air stripping was three orders of magnitude more effective than biodegradation for removing benzene and toluene in the GCW. 相似文献
6.
以竹叶眼子菜(Potamogeton malaianus)无菌系种苗为试验材料,研究了不同水体营养浓度水平(低营养:TN0.213 mg·L -1,TP 0.0093 mg·L -1;中营养:TN 0.71 mg·L -1,TP 0.031 mg·L -1;高营养:TN 7.1 mg·L -1,TP0.31 mg·L -1)对其生长与NH 4+-N的吸收动力学参数的影响。结果表明,不同浓度水体营养对竹叶眼子菜生长的影响较小,而NH 4+-N的吸收动力学参数有显著差异。竹叶眼子菜在高、中和低营养培养条件下的NH 4+-N最大吸收速率V max分别为41.1、29.1、21.1μmol·g -1·h -1,米氏常数K m分别为0.356、0.306、0.122 mmol·L -1。竹叶眼子菜营养吸收动力学与其生长环境关系紧密,在低浓度生长环境中时,竹叶眼子菜可以通过降低K m值来提高对营养离子的亲和力以满足营养需求;在高浓度生长环境中,该植物通过增大吸收潜力来适应高营养。 相似文献
7.
Mono- and dilauroyl arabitols, ribitols, xylitols and sorbitols were synthesized batchwise or continuously at 50°C or 60°C by condensation catalyzed by an immobilized Candida antarctica lipase in acetone. Continuous production was realized using a system where a column packed with sugar alcohol and a packed-bed reactor with the immobilized lipase were connected in series. The concentrations of the mono- and dilauroyl esters of each sugar alcohol became almost constant at mean residence times of 15 min or longer in the packed-bed reactor. The monolauroyl, monomyristoyl and monopalmytoyl arabitols, ribitols, xylitols and sorbitols were continuously produced using the reactor system at 60°C, and the productivity was in the range of 1.3-2.0 kg L -1-reactor·day except for the fatty acid esters of sorbitol, the productivity of which was 0.6-0.8 kg L -1-reactor·day. 相似文献
8.
以烟草悬浮细胞BY-2(Nicotiana tabacum ‘Bright Yellow-2’)为材料,研究了NaCl、PEG(6000)、低温3种非生物胁迫对细胞内ATP(intracellular ATP,iATP)和细胞外ATP(extracellular ATP,eATP)水平的影响。结果显示:50~200 mmol·L -1 NaCl处理导致烟草悬浮细胞膜通透性显著增加(P<0.05),100和200 mmol·L -1 NaCl处理时iATP和eATP水平显著降低(P<0.05)。随着PEG质量浓度的增加(50、100、200 g·L -1),烟草悬浮细胞膜通透性和eATP水平逐渐增加,其中在200 g·L -1 PEG处理时eATP水平显著增加至对照的3.4倍(P<0.05),而iATP水平则在200 g·L -1 PEG处理时显著降低至对照的0.5倍(P<0.05)。0~10℃低温处理后,烟草悬浮细胞膜通透性和iATP水平呈不同程度增加,其中0℃处... 相似文献
9.
A dual-tube dense-phase silicone rubber membrane bioreactor was investigated for control of cyclohexane-contaminated air as part of a jet propulsion (JP-8) fuel remediation investigation strategy. The reactor was seeded with a mixed bacterial consortium isolated from the water/fuel interface of a JP-8 jet fuel sample and activated sludge, capable of aromatic and cyclic compound biodegradation. Cyclohexane removal ranged from 1.1 to 28.6 mg L -1, with removal percentages ranging from 4.6% to 37.6%. Removal in the bioreactor ranged from 29.4 to 596.6 mg min -1 m -2 and measured elimination capacities ranged from 46.7 to 947.9 g m -3 h -1. Removal rates and elimination capacity increased with increasing biofilm growth and with increasing loading rates of cyclohexane. Loading rates ranged from 395.9 to 2189.5 mg min -1 m -2. Results of this study showed effective removal of cyclohexane using the membrane bioreactor, suggesting that this technology may have applicability for treating vapors contaminated with cyclic hydrocarbons. 相似文献
10.
Seawater was supplemented with NH 4+ and P to determine concentrations of N and P adequate for supporting exponential growth of bacteria utilizing crude oil, and to determine maximum rates of N and P uptake. Oil-degrading microorganisms were obtained by enrichment culture of indigenous oil-utilizing microorganisms in seawater. NH 4+ at a concentration of 5.5 µM was limiting to growth of bacteria on crude oil. Exponential growth occurred at concentrations higher than 30 µM NH 4+. The P concentration of 0.13 µM was limiting to growth of bacteria on crude oil. Exponential growth occurred at 1.8 |J,M P. The maximum NH4+ consumption rate was 426 ± 30 |J,g NH 4+ L -1 hr -1, and the maximum uptake rate of P was 48±4 µg P L -1 hr -1. Uptake of N and P with time showed zero-order kinetics, likely due to substrate solubility limitations. The uptake ratio of N:P was approximately 7:1 on a weight basis. Natural concentrations of N and P in marine and estuarine systems after hydrocarbon spillage initially may not limit oil biodegradation but may become limiting if adequate flux does not occur to replenish N and P depleted by microbial consumption. 相似文献
11.
硫酸铜常用于水产养殖的疾病防治,但当水体中的铜离子浓度超过一定范围时便对软体动物产生一定的毒害作用.研究选取椭圆背角无齿蚌( Anodonta woodiana elliptica)作为研究对象,采用苏木精-伊红染色方法进行组织石蜡切片制作,从组织学角度研究了浓度为0.01 mg·L -mg·L -1、0.1 mg·L -1、1 mg·L -1和10 mg·L -1的硫酸铜作用不同时间后椭圆背角无齿蚌的胃结构的变化.结果表明,0.01 mg·L -1硫酸铜处理7d和14d后,仅胃绒毛变短,随着硫酸铜浓度的增大和处理时间的延长,胃绒毛逐渐变短,肌层变薄,腺细胞数量减少直至空化;低于10mg·L -1的硫酸铜中毒7d和14d后,胃晶杆头直径和胃楯长度出现增大的现象. 相似文献
12.
The rate of electron transfer between reduced cytochrome ƒ and plastocyanin (both purified from parsley) has been measured as k = 3.6 · 10 7 M −1 · s −1, at 298 °K and pH 7.0, with activation parameters Δ H‡ = 44 kJ · mole −1 and Δ S‡ = +46 J · mole −1 · °K −1. Replacement of cytochrome ƒ with red algal cytochrome c-553, Pseudomonas cytochrome c-551 and mammalian cytochrome c gave rates at least 30 times slower: k = 5 · 10 5, 7.5 · 10 5 and 1.0 · 10 6 M −1 · s −1, respectively. Similar measurements made with azurin instead of plastocyanin gave k = 6 · 106 and approx. 2 · 107 M−1 · s−1 for reaction of reduced azurin with cytochrome ƒ and algal cytochrome respectively. Rate constants of 115 and 80 M−1 · s−1 were found for reduction of plastocyanin by ascorbate and hydroquinone at 298 °K and pH 7.0. The rate constants for the oxidation of plastocyanin, cytochrome ƒ, Pseudomonas cytochrome c-551 and red algal cytochrome c-553 by ferricyanide were found to be between 3 · 104 and 8 · 104 M−1 · s−1. The results are discussed in relation to photosynthetic electron transport. 相似文献
13.
1. 1.The bahavioural paradigm in which cold-exposed animals can work for pulses of infrared radiation has been extensively used in the literature, but a formula to calculate the amount of heat obtained has not been advanced. 2. 2.This paper describes a computational formula for heat influx in rats: E = 3.64 · 10−6 · n · d · I · M0.6 where E is heat influx (kJ), n is number of rewards, d is reward duration (sec), I is irradiance (mW/cm2), and M is body mass (g).
Author Keywords: Heat influx; behavioural thermoregulation; thermal radiation; whole body heating; heat transfer; rat 相似文献
14.
1. Single reduced methyl viologen (MV .+) acts as an electron donor in a number of enzyme systems. The large changes in extinction coefficient upon oxidation (λ max 600 nm; MV .+, = 1.3 · 10 4 M −1 · cm −1; oxidised form of methyl viologen (MV 2+), = 0.0) make it ideally suited to kinetic studies of electron transfer reactions using stopped-flow and standard spectrophotometric techniques. 2. A convenient electrochemical preparation of large amounts of MV.+ has been developed. 3. A commercial stopped-flow apparatus was modified in order to obtain a high degree of anaerobicity. 4. The reaction of MV.+ with O2 produced H2O2 (k > 5 · 106 M−1 · s−1, pH 7.5, 25 °C). H2O2 subsequently reacted with excess MV.+ (k = 2.3 · 103 M−1 · s−1, pH 7.5, 25 °C) to produce water. The kinetics of this reaction were complex and have only been interpreted over a limited range of concentrations. 5. The results support the theory that the herbicidal action of methyl viologen (Paraquat, Gramoxone) is due to H2O2 (or radicals derived from H2O2) induced damage of plant cell membrane. 相似文献
15.
该文探讨了基本培养基、外植体、培养条件以及植物生长调节剂配比对绒毛白蜡(Fraxinus velutina)体胚诱导的影响。结果表明,胚根是诱导体胚发生的最佳外植体;体胚诱导的最适培养基为改良MS+2 mg·L~(–1) 6-BA+0.1 mg·L~(–1) NAA、30g·L~(–1)蔗糖、5.0 g·L~(–1)琼脂;暗培养20天后进行光照培养(14小时光照/10小时黑暗),光密度为100~(–1)20μmol·m~(–2)·s~(–1),昼温度(25±2)°C,夜温度(18±2)°C;成功诱导出体细胞胚并获得再生植株,体胚诱导率可达59.8%,体胚萌发率达81.2%。壮苗最适培养基为改良WPM+0.5 mg·L~(–1) 6-BA+0.2 mg·L~(–1) ZT+0.01 mg·L~(–1) NAA。生根最适培养基为改良1/2MS+1.0 mg·L~(–1)IBA+0.05 mg·L~(–1) NAA+20 g·L~(–1)蔗糖,生根率高达97.3%,试管苗移栽成活率达97.8%。 相似文献
16.
以迷迭香悬浮培养细胞为材料,详细研究了基本培养基中添加蔗糖、麦芽糖和葡萄糖对细胞生长及次生代谢产物积累的影响,同时对不同蔗糖浓度处理的悬浮培养细胞抗氧化酶活性进行了研究。研究结果表明:在不同的糖处理中,30 g·L -1的蔗糖、70 g·L -1的麦芽糖及40 g·L -1的葡萄糖最有利于迷迭香悬浮培养细胞生长。30 g·L -1蔗糖和70 g·L -1麦芽糖处理中悬浮培养细胞的生长率分别为74.08%和72.33%,高出40 g·L -1葡萄糖处理接近3倍之多。30 g·L -1蔗糖处理的悬浮培养细胞迷迭香酸含量高出70 g·L -1麦芽糖处理228倍,略低于40 g·L -1葡萄糖处理。在不同蔗糖的处理中,随着蔗糖浓度的增加,迷迭香酸含量均呈现增加趋势,表明高浓度的蔗糖有利于悬浮培养细胞迷迭香酸的积累。在高浓度的蔗糖处理中,悬浮培养细胞H 2O 2和MDA含量明显增加,同时抗氧化酶SOD、POD及CAT的活性也明显增强,表明高浓度的蔗糖产生了渗透胁迫,这种渗透胁迫虽不利于迷迭香悬浮培养细胞的生长,但有利于次生代谢产物的积累。综合迷迭香悬浮细胞的生长率和迷迭香酸的含量,我们最终得出30 g·L -1的蔗糖最有利于迷迭香悬浮细胞的培养。 相似文献
17.
弄清土地利用和降水变化对林地土壤主要温室气体(CO 2、CH 4和N 2O)排放通量变化的影响, 是准确评估森林土壤温室气体排放能力的重要基础。该研究以常绿落叶阔叶混交林原始林、桦木( Betula luminifera)次生林和马尾松( Pinus massoniana)人工林为对象, 采用静态箱-气相色谱法研究了3种土地利用方式(常绿落叶阔叶混交林原始林、桦木次生林和马尾松人工林)和降水减少处理状况下森林土壤CO 2、CH 4和N 2O通量排放特征, 并探讨了其环境驱动机制。研究结果表明: 原始林土壤CH 4吸收通量显著高于次生林和人工林, 次生林CH 4吸收通量显著高于人工林土壤。人工林土壤CO 2排放通量显著高于原始林和次生林土壤。次生林土壤N 2O排放通量高于原始林和人工林, 但三者间差异不显著。降水减半显著抑制了3种不同土地利用方式下林地土壤CH 4吸收通量; 降水减半处理对原始林和次生林土壤CO 2排放通量均具有显著的促进作用, 而对人工林土壤CO 2排放通量具有显著的抑制作用; 降水减半处理促进了原始林和人工林林地土壤N 2O排放而抑制了次生林林地土壤N 2O排放。原始林和次生林林地土壤CH 4吸收通量随土壤温度升高显著增加, CH 4吸收通量与土壤温度均呈显著相关关系; 原始林、次生林和人工林土壤CO 2和N 2O排放通量与土壤温度均呈显著正相关关系; 土壤湿度抑制了次生林和人工林土壤CH 4吸收通量, 其CH 4吸收通量随土壤湿度增加显著减少; 原始林土壤CO 2排放通量与土壤湿度呈显著正相关关系。自然状态下, 原始林土壤N 2O排放通量与土壤湿度呈显著正相关关系, 原始林和次生林土壤N 2O排放通量与硝态氮含量呈显著相关关系。研究结果表明全球气候变化(如降水变化)和土地利用方式的转变将对北亚热带森林林地土壤温室气体排放通量产生显著的影响。 相似文献
18.
Aims It is important to study the effects of land use change and reduced precipitation on greenhouse gas fluxes (CO 2, CH 4 and N 2O) of forest soils. Methods The fluxes of CO 2, CH 4 and N 2O and their responses to environmental factors of primary forest soil, secondary forest soil and artificial forest soil under a reduced precipitation regime were explored using the static chamber and gas chromatography methods during the period from January to December in 2014. Important findings Results indicate that CH 4 uptake of primary forest soil ((-44.43 ± 8.73) μg C·m -2·h -1) was significantly higher than that of the secondary forest soil ((-21.64 ± 4.86) μg C·m -2·h -1) and the artificial forest soil ((-10.52 ± 2.11) μg C·m -2·h -1). CH 4 uptake of the secondary forest soil ((-21.64 ± 4.86) μg C·m -2·h -1) was significantly higher than that of the artificial forest ((-10.52 ± 2.11) μg C·m -2·h -1). CO 2 emissions of the artificial forest soil ((106.53 ± 19.33) μg C·m -2·h -1) were significantly higher than that of the primary forest soil ((49.50 ± 8.16) μg C·m -2·h -1) and the secondary forest soil ((63.50 ± 5.35) μg C·m -2·h -1) ( p < 0.01). N 2O emissions of the secondary forest soil ((1.91 ± 1.22) μg N·m -2·h -1) were higher than that of the primary forest soil ((1.40 ± 0.28) μg N·m -2·h -1) and the artificial forest soil ((1.01 ± 0.86) μg N·m -2·h -1). Reduced precipitation (-50%) had a significant inhibitory effect on CH 4 uptake of the artificial forest soil, while it enhanced CO 2 emissions of the primary forest soil and the secondary forest soil. Reduced precipitation had a significant inhibitory effect on CO 2 emissions of the artificial forest soil and N 2O emissions of the secondary forest ( p < 0.01). Reduced precipitation promotes N 2O emissions of the primary forest soil and the artificial forest soil. CH 4 uptake of the primary forest and the secondary forest soil increased significantly with the increase of soil temperature under natural and reduced precipitation. CO 2 and N 2O emission fluxes of the primary forest soil, secondary forest soil and artificial forest soil were positively correlated with soil temperature ( p < 0.05). Soil moisture inhibited CH 4 uptake of the secondary forest soil and the artificial forest soil ( p < 0.05). CO 2 emissions of the primary forest soil were significantly positively correlated with soil moisture ( p < 0.05). N 2O emissions of primary forest soil and secondary forest soil were significantly correlated with the nitrate nitrogen content ( p < 0.05). It was implied that reduced precipitation and land use change would have significant effects on greenhouse gas emissions of subtropical forest soils. 相似文献
19.
We have used picosecond absorption spectroscopy with low intensity (5 · 10 11–5 · 10 12 photons · pulse −1 · cm −2) continuously tunable infrared (800–900 nm) pulses to study the energy transfer dynamics in the isolated B800–850 pigment-protein complex of Rhodobacter sphaeroides. Our results suggest the following picture of the energy transfer dynamics: (i) a fast transfer, within approx. 1 ps, from BChl 800 to BChl 850; (ii) transfer among different BChl 800's with a rate which is at the most of the same order of magnitude as that of BChl 800 → BChl 850 transfer; (iii) very fast transfer ( k > 1 · 10 12 s −1) between BChl 850 molecules. Assuming Förster type of energy transfer maximum distances of about 22 and 15 Å are obtained for the BChl 800–BChl 850 and BChl 850–BChl 850 separations, respectively. 相似文献
20.
以氯代苯胺(PCA)为选择基质,用驯化技术从降解对二氯苯(p-DCB)的富集培养物中得到了以同化PCA为唯一碳源和氮源的混合微生物。将这种固定在填充床反应器中的微生物用于PCA的降解作用研究中。在该反应器里,PCA的生物降解遵循Logistic方程q=q max/(1+e α-βUv).由方程求出了主要的动力学常数,K s(半速率常数)和q max(最大比基质降解速率).于PCA降解的同时,释放氯离子到培养基中。在水力停留时间3h, 进水PCA浓度为360mg·L -1情况下,基质的体积降解率达到125mg·L -1·h -1;基质的百分去除率为91%. 相似文献
|