Inactivation of Pseudomonas aeruginosa biofilm by dense phase carbon dioxide

Dense phase carbon dioxide (DPCD) is one of the most promising techniques available to control microorganisms as a non-thermal disinfection method. However, no study on the efficiency of biofilm disinfection using DPCD has been reported. The efficiency of DPCD in inactivating Pseudomonas aeruginosa biofilm, which is known to have high antimicrobial resistance, was thus investigated. P. aeruginosa biofilm, which was not immersed in water but was completely wet, was found to be more effectively inactivated by DPCD treatment, achieving a 6-log reduction within 7 min. The inactivation efficiency increased modestly with increasing pressure and temperature. This study also reports that the water-unimmersed condition is one of the most important operating parameters in achieving efficient biofilm control by DPCD treatment. In addition, observations by confocal laser scanning microscopy revealed that DPCD treatment not only inactivated biofilm cells on the glass coupons but also caused detachment of the biofilm following weakening of its structure as a result of the DPCD treatment; this is an added benefit of DPCD treatment.     

Extraction of squalene from yeast by supercritical carbon dioxide

Squalene produced under anaerobic conditions, by a strain of Torulaspora delbrueckii was extracted from the biomass using supercritical carbon dioxide. Minimum use of solvent, lower time of isolation and a higher selectivity of extraction merit use of supercritical fluid extraction (SFE) technique over solvent extraction of squalene, as optimized and reported previously. A maximum squalene yield of 11.12 g g^–1 (dry weight) of yeast cells was obtained at a temperature of 60 °C and pressure of 250–255 bar at a constant flow rate of 0.2l min^–1 of carbon dioxide. Lyophilization prior to SFE increased the squalene yield to 430.52 g g^–1 dry weight of yeast cells, an amount that is far greater than that obtained by (2:1) chloroform–methanol solvent extraction.     

超临界CO_2流体萃取苦瓜总黄酮工艺及其抗氧化活性

利用响应面法优化超临界CO2萃取苦瓜总黄酮的工艺参数,在单因素实验基础上,以萃取时间、萃取温度及萃取压力为自变量,总黄酮提取率为响应值,采用中心组合设计的方法,研究各自变量及其交互作用对总黄酮提取率的影响。结果表明,3个因素对总黄酮提取率的影响大小依次为萃取压力、萃取温度、萃取时间。利用SAS软件和响应面分析相结合的方法模拟得到二次多项式回归方程的预测模型,确定最佳工艺条件:采用无水乙醇为夹带剂(4.0 mL/g),萃取压力33.4 MPa、萃取温度46℃、萃取时间53.2 m in。此条件下,苦瓜总黄酮提取率达到84.3%。抗氧化实验表明:超临界CO2萃取能较好保留苦瓜总黄酮的抗氧化活性,采用超临界CO2萃取法提取的苦瓜总黄酮具有较强的抗氧化活性,当质量浓度为1 mg/mL时,对DPPH自由基的清除能力与Vc相当,清除率达到93.1%。     

Effects of pressure and temperature of supercritical carbon dioxide on the extraction of triacylglycerols from plant tissue

The rate of extraction of triacylglycerols with supercritical carbon dioxide can be greatly enhanced by raising the pressure of the fluid to 600 bar, or higher, and its temperature to 60°C, or higher. Both the amount of carbon dioxide and the time required for complete extraction are reduced at such high pressures and temperatures.     

北五味子果实超临界CO2萃取工艺的研究

通过正交设计的试验方法,探讨了超临界CO₂法萃取五味子果实中木脂素的工艺条件,确定了最佳工艺条件为萃取压力30 Mpa,萃取温度50℃,萃取时间120 min。     

超临界二氧化碳的四个应用方向

综述了超临界CO2的四个主要应用方向,即萃取、细胞破壁和微粒制造、反应溶剂以及SCCO2洗涤,着重总结了在烟草工业上的应用。对国内外的应用现状和应用前景给予了评述,并给出CO2温度、压力、密度的关系式。     

Simultaneous Measurement of Fluoroquinolones in Eggs by a Combination of Supercritical Fluid Extraction and High Pressure Liquid Chromatography

Simultaneous detection of the fluoroquinolone antibiotics ciprofloxacin, enrofloxacin, ofloxacin, and norfloxacin in eggs by a combination of supercritical fluid extraction (SFE) and high pressure liquid chromatography (HPLC) was studied. Lipid matrices that have been considered to result in poor extraction and isolation of fluoroquinolones in eggs were removed first by SFE with supercritical CO₂ alone, and then the fluoroquinolones were extracted by SFE with supercritical CO₂ containing 20% (v/v) methanol for HPLC analysis. A time-course study of the extraction of lipid matrices of eggs suggested that the SFE method successfully removed the matrices within 20 min. When the fluoroquinolones added to control eggs were extracted by SFE, the extraction efficiency was similar to that by the solvent extraction method, giving the recovery percentages from 83 to 96% in a 40 min-extraction time. The fluoroquinolones extracted from eggs by SFE were analyzed simultaneously by HPLC equipped with a fluorescence detector with detection sensitivity at about 10 ppb for the detection limit. The standard calibration profiles of fluoroquinolones showed linear responses to HPLC, showing more than 0.995 for the mean r ² value. This is the first report of the simultaneous measurement of fluoroquinolones in eggs by a combination of SFE and HPLC. Using the SFE method allowed us to avoid extensive sample preparation such as solvent extraction and chromatographic cleanup that are basically required in extraction of fluoroquinolones.     

Supercritical carbon dioxide extraction of hydrocarbons from the microalgaBotryococcus braunii

Samples of the microalgaBotryococcus braunii were submitted to supercritical fluid extraction with carbon dioxide at 40 °C and pressures of 12.5, 20.0 and 30.0 MPa. The extraction yield and the fraction of the hydrocarbons in the extracts both increased with pressure and at 30 MPa these compounds were obtained rapidly. This behaviour is associated with the localization of the hydrocarbons outside the cell wall. In the extracts, which are fluid, golden and limpid, chlorophyll and phospholipids were not detected.Author for correspondence     

Exploiting the pressure effect on lipase-catalyzed wax ester synthesis in dense carbon dioxide

The present work focuses on the thermodynamic interpretation of the lauryl oleate biosynthesis in high-pressure carbon dioxide. Lipase-catalyzed lauryl oleate production by oleic acid esterification with 1-dodecanol over immobilized lipase from Rhizomucor miehei (Lipozyme RM IM) was successfully performed in a sapphire window batch stirred tank reactor (BSTR) using dense CO(2) as reaction medium. The experiments were planned to elucidate the pressure effect on the reaction performance. With increasing the pressure up to 10 MPa, the catalytic efficiency of the studied enzyme improved rising up to a maximum and decreased at higher pressure values. Kinetic observations, exhibiting that dense CO(2) expanded reaction mixture in subcritical conditions led to higher performance than when diluted in a single supercritical phase, were elucidated by phase-equilibrium arguments. The experimental results were justified with emphasis on thermodynamic interpretation of the studied system. Particularly, the different reaction performances obtained were related to the position of the operating point with respect to the location of liquid-vapor phase boundaries of the reactant fatty acid/alcohol/CO(2) ternary system. The outlook for exploitation of CO(2) expanded phase at lower pressure compared to supercritical phase, with heterogeneous system in which the solid catalyst particles are exposed to dense CO(2) expanded reaction mixture, in developing new biotransformation schemes is promising.     

响应面法对超临界CO_2萃取茶籽仁油的工艺优化

为了保证茶籽油的原生态品质,研究了茶籽仁油的超临界CO2萃取技术,并运用响应面法对其萃取压力、温度和时间等工艺条件进行了优化分析,得到的最佳工艺条件是在33 MPa压力和43℃温度下连续萃取时间2 h。此条件下的萃取得率为39.6%、出油效率达86.5%,所得茶籽油只需简单的脱酸处理即达到国标GB11765—2003规定的压榨一级茶籽油水平。     

土壤有机碳和外源添加碳对水稻土土体呼吸的影响

土体呼吸输出碳来源于土壤固有有机碳和外源添加碳,而以往关于不同施肥措施对水稻土碳排放的研究少有区分碳的来源。本试验利用一个长达30年的水稻土定位试验,在保证原有定位试验继续正常开展的前提下变更部分施肥处理,得到继续施用高量有机肥(HOM)、施用常量有机肥30年后改施高量有机肥(N-H)、继续施用常量有机肥(NOM)、施用化肥30年后改施常量有机肥(C-N)、施用高量有机肥30年后改施化肥(H-C)、施用常量有机肥30年后改施化肥(N-C)、继续施用化肥(CF)等7种施肥处理。通过观测早稻生长期间原有施肥和改施肥处理土体CO2排放通量(FCO2),研究不同后续施肥对水稻土FCO2的影响,以期探讨土壤原始有机碳和外源添加碳对土壤FCO2的影响。结果表明:7种不同施肥处理土体CO2平均排放通量(F珔CO2)分别为85.34、69.10、51.27、49.15、14.89、12.92和11.59 mg C.m-2.h-1;对施用无机肥料和常量有机肥料的土体而言,土壤本身有机碳含量对F珔CO2无显著影响,但对施用高量有机肥的土体而言,土壤本身的高有机碳含量会增强F珔CO2;CO2排放通量(Y)与添加外源碳量(x)之间符合指数方程:Y=13.33e1.719 x(R2=0.967,n=21),施入的外源有机碳对土体FCO2产生极显著影响;当季外源添加碳以CO2-C矿化分解释放的碳占其总碳量的14%左右,且该分解率受土壤有机碳含量和有机物料添加量的影响较小。     

超临界CO2萃取烟叶中茄尼醇的工艺研究

采用超临界二氧化碳萃取烟叶中的茄尼醇,考察了萃取过程温度、压力、二氧化碳流量、萃取方式、夹带剂种类及其用量对萃取过程的影响。采用四因素三水平的正交设计,以茄尼醇的提取率为指标,对萃取条件进行了优化。并建立了能较准确测定烟叶中游离茄尼醇含量的方法,采用高效液相色谱对萃取产物进行了分析。以探索提高提取率的方法,为其工业化生产提供参考。结果表明:最佳萃取工艺条件为:甲醇为夹带剂,萃取温度45℃,萃取压力25MPa,CO2流量15kg·h-1。在最佳工艺条件下茄尼醇的提取率为:92.1%。     

超临界二氧化碳萃取鸢尾油的工艺条件研究

本文采用L9（3^4）正交实验考察了二氧化碳超临界萃取中萃取压力、萃取温度和萃取时间对鸢尾精油提取率的影响。结果表明各影响因子的影响顺序为：压力〉时间〉温度;当原料的颗粒度为60-80目、CO2流量为20．0m^3/h时,用超临界二氧化碳萃取鸢尾精油的最佳工艺条件为：萃取压力26．0MPa,萃取温度55．0℃,萃取完成时间为2．5h,此条件下鸢尾香根中鸢尾油的萃取率高达12．71％,得到的精油中鸢尾酮的含量为39．95％,与索氏法和微波提取法相比,超临界萃取具有提取率高和产品质量好的优点。     

Calculation of diffusion coefficient for supercritical carbon dioxide and carbon dioxide+naphthalene system by molecular dynamics simulation using EPM2 model

NVT ensemble molecular dynamics (MD) simulation has been applied to calculate the self-diffusion coefficients of carbon dioxide and the tracer diffusion coefficients of naphthalene in supercritical carbon dioxide. The simulation was carried out in the pressure range from 8 to 40 MPa. The elementary physical model proposed by Harris and Yung was adopted for carbon dioxide and some approximation models were used for naphthalene. The systems of MD simulation for carbon dioxide consist of 256 particles. One naphthalene molecule was added for carbon dioxide+naphthalene system. The system can be assumed to be an infinite dilution condition for carbon dioxide+naphthalene system and the mutual diffusion coefficients are equal to the tracer diffusion coefficients of naphthalene. The self-diffusion coefficients of carbon dioxide and the tracer diffusion coefficients of naphthalene in supercritical carbon dioxide can be calculated by mean square displacement. The calculated results of diffusion coefficients showed good agreement with the experimental data without adjustable parameters.     

Efficient phase separation and product recovery in organic‐aqueous bioprocessing using supercritical carbon dioxide

Biphasic hydrocarbon functionalizations catalyzed by recombinant microorganisms have been shown to be one of the most promising approaches for replacing common chemical synthesis routes on an industrial scale. However, the formation of stable emulsions complicates downstream processing, especially phase separation. This fact has turned out to be a major hurdle for industrial implementation. To overcome this limitation, we used supercritical carbon dioxide (scCO₂) for both phase separation and product purification. The stable emulsion, originating from a stereospecific epoxidation of styrene to (S)‐styrene oxide, a reaction catalyzed by recombinant Escherichia coli, could be destabilized efficiently and irreversibly, enabling complete phase separation within minutes. By further use of scCO₂ as extraction agent, the product (S)‐styrene oxide could be obtained with a purity of 81% (w/w) in one single extraction step. By combining phase separation and product purification using scCO₂, the number of necessary workup steps can be reduced to one. This efficient and easy to use technique is generally applicable for the workup of biphasic biocatalytic hydrocarbon functionalizations and enables a cost effective downstream processing even on a large scale. Biotechnol. Bioeng. 2010;107:642–651. © 2010 Wiley Periodicals, Inc.     

超临界CO2萃取烟叶中茄尼醇的工艺研究

采用超临界二氧化碳萃取烟叶中的茄尼醇,考察了萃取过程温度、压力、二氧化碳流量、萃取方式、夹带剂种类及其用量对萃取过程的影响。采用四因素三水平的正交设计,以茄尼醇的提取率为指标,对萃取条件进行了优化。并建立了能较准确测定烟叶中游离茄尼醇含量的方法,采用高效液相色谱对萃取产物进行了分析。以探索提高提取率的方法,为其工业化生产提供参考。结果表明：最佳萃取工艺条件为：甲醇为夹带剂,萃取温度45℃,萃取压力25 MPa,CO₂流量15 kg·h^-1。在最佳工艺条件下茄尼醇的提取率为：92.1%。     

Activity and stability of immobilised soybean lipoxygenase-1 in aqueous and supercritical carbon dioxide media

The activity of immobilised soybean lipoxygenase-1 (LOX-1) was studied in aqueous and supercritical carbon dioxide (SCCO₂) media for the production of 13S-hydroperoxyoctadecadenoic acid (13S-HPODE). In SCCO₂, it was optimal at 33 °C and 25 MPa. A higher space-time yield of 5.7×10^–3 Ms^–1 mg^–1 LOX-1 for 13S-HPODE was obtained in SCCO₂ compared to only 5×10^–5 Ms^–1 mg^–1 LOX-1 in aqueous medium. The stability of immobilised LOX-1 was only significantly affected by the pressurisation and depressurisation steps during reactions in SCCO₂.     

超临界CO2提取茶籽油的工艺及其成分分析

对超临界CO2工艺提取茶籽油进行研究,选择萃取压力、温度、时间、分离釜Ⅰ压力为影响因素,茶籽油的提取率为试验指标,采用多因素多水平可视化分析方法对数据进行分析,得出最佳工艺范围：萃取压力2.5×107～3.0×107Pa、温度30～35℃、时间110～140 min、分离釜Ⅰ压力4.0×106～5.0×106Pa。并用气相色谱-质谱法测定茶籽油中的各个成分及含量,发现茶籽油中单不饱和脂肪酸主要为油酸,多不饱和脂肪酸主要为亚油酸,饱和脂肪酸主要为棕榈酸和硬脂酸。     

Supercritical carbon dioxide extraction,fluorimetric and electrochemical high performance liquid chromatrographic detection of vitamin E from Hordeum vulgare L.

A supercritical fluid extraction (SFE), method has been applied to extract the natural vitamin E components, tocopherols and tocotrienols, from fruits of Hordeum vulgare L. The fractions were monitored by analytical high performance liquid chromatography using fluorimetric and electrochemical detectors. High yields, and clear and purified extracts were obtained by SFE; compared with the n-hexane extract, the SFE extract was lighter in colour and more concentrated in vitamin E components. © 1998 John Wiley & Sons, Ltd.     

Response of soil carbon dioxide fluxes,soil organic carbon and microbial biomass carbon to biochar amendment: a meta‐analysis

Biochar as a carbon‐rich coproduct of pyrolyzing biomass, its amendment has been advocated as a potential strategy to soil carbon (C) sequestration. Updated data derived from 50 papers with 395 paired observations were reviewed using meta‐analysis procedures to examine responses of soil carbon dioxide (CO₂) fluxes, soil organic C (SOC), and soil microbial biomass C (MBC) contents to biochar amendment. When averaged across all studies, biochar amendment had no significant effect on soil CO₂ fluxes, but it significantly enhanced SOC content by 40% and MBC content by 18%. A positive response of soil CO₂ fluxes to biochar amendment was found in rice paddies, laboratory incubation studies, soils without vegetation, and unfertilized soils. Biochar amendment significantly increased soil MBC content in field studies, N‐fertilized soils, and soils with vegetation. Enhancement of SOC content following biochar amendment was the greatest in rice paddies among different land‐use types. Responses of soil CO₂ fluxes and MBC to biochar amendment varied with soil texture and pH. The use of biochar in combination with synthetic N fertilizer and waste compost fertilizer led to the greatest increases in soil CO₂ fluxes and MBC content, respectively. Both soil CO₂ fluxes and MBC responses to biochar amendment decreased with biochar application rate, pyrolysis temperature, or C/N ratio of biochar, while each increased SOC content enhancement. Among different biochar feedstock sources, positive responses of soil CO₂ fluxes and MBC were the highest for manure and crop residue feedstock sources, respectively. Soil CO₂ flux responses to biochar amendment decreased with pH of biochar, while biochars with pH of 8.1–9.0 had the greatest enhancement of SOC and MBC contents. Therefore, soil properties, land‐use type, agricultural practice, and biochar characteristics should be taken into account to assess the practical potential of biochar for mitigating climate change.