均匀设计法优选芝麻油提取新工艺

本文通过超临界CO2提取芝麻油的均匀设计实验和微波和超声波诱导提取芝麻油的正交实验比较,考察影响提取的主要因素,寻求最佳萃取工艺。超临界CO2萃取最佳工艺条件为：压力32MPa,温度60℃,CO2流量31kg／h,萃取时问80min,得率46．39％;微波萃取最佳工艺条件为：溶剂为丙酮,物料与溶剂比例1：7,辐射时间7min,辐射功率810W,得率23．01％。超声波萃取最佳工艺条件为：物料与溶剂比例1：7,溶剂为石油醚,浸泡时间30h,得率23．99％。结果表明超临界CO2萃取芝麻油品质最好,而且萃取也最高,质量最稳定。     

硫代葡萄糖苷及其降解产物异硫代氰酸盐

硫代葡萄糖苷是一种含硫的次级代谢产物,广泛分布于十字花科植物中。不同的栽培种、不同的生理阶段、不同的组织部位以及不同的栽培条件,都会使植物中含有的硫代葡萄糖苷的含量和成分有所变化。当硫代葡萄糖苷经葡萄糖硫苷酶作用时会发生降解,生成异硫代氰酸盐等产物。采后的一系列处理会影响植物中硫代葡萄糖苷的含量。硫代葡萄糖苷的降解产物异硫代氰酸盐作为一种化学预防剂,能抑制阶段Ⅰ酶（phase Ⅰ enzyme）,诱导阶段Ⅱ酶（phaseⅡenzyme）,从而防止癌症的发生。目前对硫代葡萄糖苷的鉴定方法主要是高效液相色谱法,气相色谱法等。     

超临界CO2萃取鱼腥草的挥发油成分

从萃取的压力、温度、流量和时间等条件探讨超临界CO2萃取对鱼腥草(Houttuynia cordata Thunb.)挥发油萃取率的影响,确定最佳萃取条件为萃取压力20mPa、温度35℃、CO2流量40kg/h和萃取时间80min,鱼腥草挥发油得率为1．76％。而水蒸气蒸馏提取和石油醚提取的得率分别为0．05％和0．08％。超临界CO2法萃取的鱼腥草挥发油收率高,萃取时间短。     

黑芥子酶研究进展

黑芥子酶又称黑芥子硫苷酸酶,广泛存在于自然界。它能催化硫代葡萄糖苷水解成为葡萄糖和不稳定的中间物配基,此配基易重排形成异硫氰化合物,硫氰化合物,腈,口恶唑烷硫酮等有毒物质。当植物受到昆虫,哺乳动物或病源伤害时,黑芥子酶与硫代葡萄糖苷混合,释放有毒的水解产物。因此认为黑芥子酶-硫代葡萄糖苷系统是植物重要的防御系统。另一方面,黑芥子酶催化硫代葡萄糖苷所生成的有毒物质,在一定程度上也影响了十字花科油料及蔬菜作物的品质,因此,引起了对黑芥子酶及硫代葡萄糖苷研究的重视。本文仅对黑芥子酶的研究概况作一综述。1　黑芥子酶的…     

植物芥子酶研究进展

芥子酶防御系统为白花菜目植物特有．由芥子酶及其底物硫代葡萄糖苷组成．芥子酶和硫代葡糖苷分别储藏在不同的细胞中,在受到病虫侵袭时,底物和酶相遇,硫代葡糖苷被降为有毒化合物,起防御作用．对植物芥子酶防御系统研究进展进行了综述,包括基因家族的结构、基因的表达调控、芥子酶的细胞定位、植物以外其它生物的芥子酶、硫代葡糖苷／芥子酶系统起源进化以及其可能功能等．     

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。     

超临界CO2萃取百合花挥发油的工艺研究

本文介绍了超临界CO2萃取百合花中挥发油的提取分离工艺,重点研究了超临界CO2萃取压力、温度、时间对出油率的影响。正交试验结果表明：影响超临界CO2萃取的主要因素为C3〉A2〉B2（A为萃取压力,B为萃取温度,C为萃取时间）;最佳工艺参数：SC-CO2萃取压力为18MPa,温度为50℃,时间为90min,流量为25L／min,所得百合花挥发油的出油率高达2．92％。     

植物中硫代葡萄糖苷生物代谢的分子机制

硫代葡萄糖苷是十字花科植物中重要的次生代谢物。它在内源芥子酶作用下水解为具有不同生理功能的活性物质。现从分子水平综述硫代葡萄糖苷生物合成、降解反应及其代谢调控的研究进展,为提高植物抗病性和改善营养品质等方面研究提供一定的理论依据。     

黑芥子酶研究进展

综述了黑芥子酶的研究进展,包括黑芥子酶催化硫代葡萄糖苷的水解产物对动植物和人体的作用;黑芥子酶的性质、提纯技术、活性测定、同工酶的基因家族;产黑芥子酶的植物、动物和微生物等。部分硫代葡萄糖苷可经黑芥子酶水解成有抗癌作用的异硫代氰酸盐。可通过测定葡萄糖的生成量或底物硫代葡萄糖苷浓度的变化来确定黑芥子酶的活性。十字花科等植物,以十字花科植物为食的拟步行虫、黄条跳甲、甘蓝蚜虫、小菜蛾、粉纹夜蛾等昆虫,啤酒酵母、交链孢霉属、茎点霉等真菌,以及多型拟杆菌等肠道细菌都有黑芥子酶。     

西兰花中β-硫代葡萄糖苷总量的测定

通过内源和外源芥子酶酶解硫代葡萄糖苷产生的葡萄糖的测定,间接测出西兰花中β-硫代葡萄糖苷总量,并对测定的影响因素进行了研究,与吡啶滴定法对比实验表明,该法准确可靠,操作简便。     

Leaf surface wax layers of Brassicaceae lack feeding stimulants for Phaedon cochleariae

Numerous reports have indicated that glucosinolates are important stimulants for specialist herbivores feeding on Brassicaceae, and that these metabolites might be present on the plant surface and thereby detectable by an alighting insect. We investigated the outermost layer of leaves of two species of Brassicaceae, Brassica napus L. var. ‘Martina’ and Nasturtium officinale R. Br., using two highly selective extraction methods. When the epicuticular wax layer was mechanically removed with gum arabic, no glucosinolates were detectable in the lower and upper leaf surfaces. Extracting the leaf surfaces with a threefold short rinse with chloroform/methanol/water (2 : 1 : 1 vol/vol/vol) led to varying results, depending on the light conditions under which plants had been kept in the period prior to extraction. In plants kept under light, glucosinolates were detectable in a first extraction in minor concentrations, with increasing amounts in a second and third extraction. In plants kept in darkness, glucosinolates were almost absent in the first extraction. We postulate that the polar glucosinolates are washed from the inner leaf tissue through open stomata to the outside during solvent extraction, but are not naturally present in the outermost wax layer. The response of the crucifer specialist Phaedon cochleariae (F.) (Coleoptera: Chrysomelidae) to leaf surfaces of the host plants B. napus and N. officinale and to a glucosinolate was tested. Adults preferred both the adaxial and abaxial leaf surfaces of host plants that had been treated with gum arabic in order to remove the epicuticular waxes over intact surfaces. Waxes may therefore prevent direct contact with the stimulants. Sinigrin (allyl glucosinolate) and/or surface extracts of N. officinale leaves applied on Pisum sativum leaf discs did not evoke feeding, but feeding did occur when total leaf extracts of B. napus or N. officinale were applied on this non‐host. We conclude that glucosinolates might only act as feeding stimulants for P. cochleariae in concert with compounds other than surface waxes.     

Selective separation and purification of two lipases from chromobacterium viscosum using AOT reversed micelles

Selective separation and purification of two lipases form Chromobacterium viscosum were carried out by liquid-liquid extraction using a reversed micellar system. Optimum parameters for extraction were determined using a 250 mM AOT micellar solution in isooctane. Complete separation of the two lipases was achieved at pH 6.0 with a 50mM potassium phosphate buffer solution containing 50 mM KCI. By adding 2.5% by volume of ethanol to the lipase-loaded micellar solution, 85% of the extracted lipase could be recovered in a new aqueous phase, 50 mM K(2)HPO(4) with 50 mM KCl, at pH 9.0. Lipase A was purified 2.6-fold with a recovery of 86%, and lipase B by 1.5-fold with a recovery of 76%.     

Studies on the extraction and back-extraction of a recombinant cutinase in a reversed micellar extraction process

This work deals with the extraction and back-extraction of a recombinant cutinase using AOT reversed micelles in isooctane. The effect of pH, ionic strength, AOT concentration and temperature on the extraction and back-extraction of the cutinase was investigated. High extraction (97%) of the cutinase was achieved at pH 7.0 with a 50 mM Tris-HCl buffer solution containing 100 mM KCl, but a low activity was detected in the reversed micellar phase. At pH 9.0, cutinase was extracted (75%) to the reversed micelles with higher activity. Cutinase was recovered (50%) from a reversed micellar phase (100 mM AOT/isooctane) into a 50 mM Tris-HCl buffered solution at pH 9.0 with 100 mM KCl, and 20°C. Protein and cutinase activity global yields of 38 and 45%, respectively, were obtained for the global process, extraction and back-extraction steps, using low ionic strength, pH 9.0, 100 mM AOT and 20°C.Maria das Graças Carneiro da Cunha acknowledges a Ph.D. fellowship from Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) and Centro de Pesquisas Aggeu Magalhães, Brasil. This work was partly financed by the BRIDGE Programme (Contract BIOT-CT91-0274(DTEE)).     

Liquid–liquid extraction of an extracellular alkaline protease from fermentation broth using aqueous two-phase and reversed micelles systems

Summary The study of recovery of an extracellular alkaline protease from fermentation broth produced by Norcadiopsis sp, was carried out with liquid–liquid extraction through sodium di-(2-ethylhexyl) sulphosuccinate/isooctane reversed micelles systems and aqueous two-phase systems (polyethylene glycol/potassium phosphate). The best conditions for extraction and back-extraction with the reversed micelles system was obtained at pH 9.0 and pH 5.0, respectively, showing a yield of protein of 6.16%, a specific activity of 4.10 U/ml and a purification factor of 1.80. The studies using aqueous two-phase systems of polyethylene glycol/potassium phosphate at pH 10.0 showed purification factors of 2 and 5, and protein yield of 11 and 4%, respectively, for polyethylene glycol 550/potassium phosphate and polyethylene glycol 8000/potassium phosphate. The results indicate that the aqueous two-phase systems are more attractive as a first step in the isolation and purification processes.     

Recovery of a recombinant cutinase with reversed micelles in a continuous perforated rotating disc contactor

Summary A continuous perforated rotating disc contactor was used for the extraction of a recombinant cutinase from an aqueous solution to a reversed micellar phase of AOT in isooctane. Cutinase was extracted to the organic phase with protein yield of 78% after 70 minutes of operation.     

Metabolic engineering of valine- and isoleucine-derived glucosinolates in Arabidopsis expressing CYP79D2 from Cassava

Glucosinolates are amino acid-derived natural products that, upon hydrolysis, typically release isothiocyanates with a wide range of biological activities. Glucosinolates play a role in plant defense as attractants and deterrents against herbivores and pathogens. A key step in glucosinolate biosynthesis is the conversion of amino acids to the corresponding aldoximes, which is catalyzed by cytochromes P450 belonging to the CYP79 family. Expression of CYP79D2 from cassava (Manihot esculenta Crantz.) in Arabidopsis resulted in the production of valine (Val)- and isoleucine-derived glucosinolates not normally found in this ecotype. The transgenic lines showed no morphological phenotype, and the level of endogenous glucosinolates was not affected. The novel glucosinolates were shown to constitute up to 35% of the total glucosinolate content in mature rosette leaves and up to 48% in old leaves. Furthermore, at increased concentrations of these glucosinolates, the proportion of Val-derived glucosinolates decreased. As the isothiocyanates produced from the Val- and isoleucine-derived glucosinolates are volatile, metabolically engineered plants producing these glucosinolates have acquired novel properties with great potential for improvement of resistance to herbivorous insects and for biofumigation.     

Mechanism of extraction of chymotrypsin into isooctane at very low concentrations of aerosol OT in the absence of reversed micelles

Chymotrypsin is easily extracted from an aqueous solution into isooctane containing the anionic surfactant aerosol OT (AOT). The concentration of AOT needed to efficiently extract 0.5 mg/mL CMT is as low as 1 mM and as low as 0.2 mM AOT was sufficient to extract the protein into isooctane. The extraction process was unaffected by 10% (v/v) ethyl acetate in the isooctane phase. Moreover, spectroscopic analysis by electron paramagnetic resonance indicated that CMT did not exist inside a discreet water pool of a reversed micelle. Calculations of the number of AOT molecules associated per extracted CMT molecule indicate that only ca. 30 surfactant molecules interact with the protein, a value too low for reversed micellar incorporation of the protein in isooctane. These studies suggested that reversed micelles do not need to be involved in the actual transfer of the protein from the aqueous to the organic phase and protein solubilization in the organic phase is possible in the absence of reversed micelles. Based on these findings, a new mechanism has been proposed herein for protein extraction via the phase transfer method involving ionic surfactants. The central theme of this mechanism is the formation of an electrostatic complex between CMT and AOT at the aqueous/organic interface between AOT and CMT, thereby leading to the formation of a hydrophobic species that partitions into the organic phase. Consistent with this mechanism, the efficiency of extraction is dependent on the interfacial mass transfer, the concentrations of CMT and AOT in the aqueous and organic phases, respectively; the ionic strength of the aqueous phase; and the presence of various cosolvents. (c) 1994 John Wiley & Sons, Inc.     

Study of the factors affecting the extraction of soybean protein by reverse micelles

In this work, the forward and back extraction of soybean protein by reverse micelles was studied. The reverse micellar systems were formed by anionic surfactant sodium bis(2-ethyl hexyl) sulfosuccinate (AOT), isooctane and KCl solution. The effects of AOT concentration, aqueous pH, KCl concentration and phase volume ratio on the extraction efficiency of soybean protein were tested. Suitability of reverse micelles of AOT and Triton-X-100/AOT mixture in organic solvent toluene for soybean protein extraction was also investigated. The experimental results lead to complete forward extraction at the AOT concentration 120 mmol l⁻¹, aqueous pH 5.5 and KCl concentration 0.8 mol l⁻¹. The backward extraction with aqueous phase (pH 5.5) resulted in 100% extraction of soybean protein from the organic phase.     

Isolation and detection of steroids from human urine by molecularly imprinted solid-phase extraction and liquid chromatography

Naturally occurring steroids such as progesterone, testosterone and 17β-estradiol were analyzed in this study. These bio-identical molecules paradoxically can be either beneficial or harmful. Unfortunately as growth promoters can be toxic and cancerogenic at elevated levels. Due to difficulty in monitoring at trace quantities of these hormones in biological matrices specific adsorption materials molecularly imprinted polymers (MIPs) were used for preconcentration and clean up in sample preparation step. A non-covalent imprinting approach was used for bulk polymerization of progesterone, testosterone and 17β-estradiol imprinted polymers. Synthesis of MIPs was achieved by thermal, UV and γ irradiation initiated polymerization whereby were used methacrylic acid (MAA), 4-vinylpyridine (4-VP) as functional monomers, ethylene glycol dimethacrylate (EDMA), trimethylolpropane trimethacrylate (TRIM) as cross-linking agents and acetonitrile, isooctane–toluene (1:99, v/v) and chloroform as porogen solvents. It was also used as initiator 2,2′-azobis(2-methylpropionitrile) (AIBN) or benzyl methyl ether (BME). The MIPs were applied as selective sorbents in solid-phase extraction (SPE). Molecularly imprinted solid-phase extraction (MISPE) considered as hyphenated technique were applied in extraction step before HPLC-DAD analysis of steroids from human urine.     

Purification of industrial alphaamylase by reversed micellar extraction

The purification of industrial alpha-amylase by liquid-liquid extraction with Aliquat 336 reversed micellar solution as the extractant was studied. Seven kinds of Aliquat 336 reversed micellar solution, formed by using seven kinds of straight chain alkyl alcohols as cosolvent, have been utilized to extract industrial a-amylase. It was found that these seven kinds of reversed micellar solution can all achieve a high protein transfer efficiency in the forward extraction process. After a full forward and backward extraction cycle, however, only the reversed micelles with n-butanol as the cosolvent was found to be able to maintain the activity of alpha-amylase in the stripping solution. By using the reversed micelles of Aliquat 336/isooctane/1% (v/v) n-butanol to perform a full extraction cycle, it was found that 85% of the total activity of alpha-amylase in the industrial a-amylase could be recovered at the end of an extraction cycle and the specific activity of alpha-amylase could be concentrated about 1.5-fold; meanwhile, most of the neutral protease in the industrial a-amylase could be removed. The separation factor of alpha-amylase to neutral protease at the end of an extraction cycle can reach about 10. (c) 1995 John Wiley & Sons, Inc.