树脂分离技术在酶法制备1,3-丙二醇中的应用

从几种吸附树脂中筛选出了树脂DA201。树脂DA201对酶、辅酶吸附较少(吸附率分别为13.13%,14.5%)且对酶活无较大破坏,对产物1,3-丙二醇(1,3-PD)与二羟基丙酮(DHA)吸附较多(吸附率分别为23%,27%)。利用树脂DA201进行产物的富集分离及酶、辅酶回流再利用,实现伴有辅酶NADH再生的1,3-PD酶法连续反应。在底物浓度为1 g/L时,树脂质量浓度为底物浓度的4.8倍、吸附时间为6 h,树脂DA201对底产物有较好的吸附分离效果。在此条件下进行1,3-PD的2个批次连续制备,第1、第2批次1,3-PD转化率分别为42.9%、35.5%,总转化率为39.72%。实验结果说明,吸附树脂对底产物、酶与辅酶具有一定的分离作用,利用树脂的分离作用可有效地实现伴有辅酶再生的酶催化反应的连续进行。     

烟草叶片组织块悬浮培养合成辅酶Q_(10)的研究

以新鲜烟草叶片制得的组织块为研究对象,建立了一种烟叶组织块悬浮培养合成辅酶Q10的方法。考察了培养温度、pH值、培养时间对辅酶Q10合成的影响。另外,采用均匀设计法对培养液中烟酸、盐酸硫胺素、半胱氨酸、对羟基苯甲酸、硫酸镁质量浓度进行了优化。在最适的培养条件下,烟草叶片组织块中辅酶Q10的质量分数达到208.09μg/g,比烟草叶片中的初始质量分数提高了18.7倍。文中建立的烟草叶片组织块悬浮培养合成辅酶Q10的方法具有周期短、操作简单的特点,是一种高效生产辅酶Q10的方法。     

Coimmobilization of malic enzyme and alanine dehydrogenase on organic–inorganic hybrid gel fibers and the production of L‐alanine from malic acid using the fibers with coenzyme regeneration

Malic enzyme (EC 1.1.1.39) and alanine dehydrogenase (EC 1.4.1.1) were entrap‐immobilized on hybrid gel fibers of cellulose acetate (CA) and zirconium (Zr) alkoxide by air‐gap wet spinning. The production of L ‐alanine from malic acid with coenzyme regeneration was examined with the enzymes immobilized on the fibers. The productivity of L ‐alanine of the immobilized enzymes decreased to approximately one‐fifth of that of free enzymes, but the CA–Zr‐fiber‐immobilized enzymes retained a high level of productivity after repeated use. Reduced form of nicotinamide adenine dinucleotide (NADH) recycling also occurred effectively for the enzymes immobilized on the fiber. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010     

Gas-Trennung mit Membranen

Gas Separation with membranes . Gas separation with membranes has already been tested in numerous fields of application, e. g. uranium enrichment or H₂ separation. In many of these processes the mass transfer units, so-called permeators, have to be connected in tandem in order to achieve high concentrations. A most economical operating method provides for each case an optimization of the cascades with regard to the membrane materials, construction and design of module. By utilization of the concentration gradient along the membrane a new process development has been accomplished – the continuously operating membrane rectification unit. Investment and operating costs can be reduced considerably for a number of separating processes by combining a membrane rectification unit with a conventional recycling cascade. However, the new procedure requires that the specifications for the module construction, flow design, and membrane properties be reconsidered.     

An efficient strategy overcoming the bottleneck in Candida parapsilosis catalyzing stereoinversion from (R)‐1‐phenyl‐1, 2‐ethanediol to the corresponding counterpart

BACKGROUND: Microbial stereoinversion has been widely used for the biosynthesis of numerous chiral compounds. However, little work has been done to improve the efficiency of microbial stereoinversion. This study investigated the bottleneck in the deracemization of 1‐phenyl‐1,2‐ethanediol (PED), and then the efficiency and the sustainability of biocatalyst was improved significantly by using a strategy. RESULTS: When (S)‐PED concentration exceeded 17.5 g L^?1, it strongly inhibited deracemization. Furthermore, the deficiency of NADPH regeneration also limited such reaction. To overcome these limitations, extractive biocatalysis was developed using adsorbent resin NKII combined with xylose addition for cofactor regeneration. Compared with the initial reaction condition, which only afforded (S)‐PED with 35% optical purity after the first batch reaction at 30 g L^?1 substrate concentration, the cells in the new system could be reused three times and the optical purity remained at a high level of 95%. CONCLUSION: Product inhibition and coenzyme regeneration had a significant effect on catalytic activity of Candida parapsilosis. By using a resin and D‐xylose, the efficiency and reusability of whole‐cell catalyst can be considerably improved, which would be helpful for effective synthesis of high value chiral intermediates. Copyright © 2009 Society of Chemical Industry     

Hyperazeotropic ethanol salted-out by extractive distillation. Theoretical evaluation and experimental check

A distillation process for the production of hyperazeotropic ethanol from a dilute wine obtained from the fermentation of biomass has been studied. This process utilizes the coupling of a soft preconcentration stage and of a dehydration stage based on the salting-out effect produced by calcium chloride on the ethanol in an aqueous solution, with the disappearance of the azeotrope. The salt is employed in a close cycle, due to the presence of a regeneration stage, therefore no consumption of calcium chloride is noticed.

The distillation process utilizes one column consisting of two sections operating at different pressures in order to reach an efficient heat recovery.

In this paper, a simplified flow-sheet of the process and the principal operating conditions of the distillation column are illustrated. When compared with other processes, conventional or under development, this one is characterized by the promising reduction of the specific energy requirement.

The operating conditions chosen for the distillation with salt have been experimentally checked using a laboratory column running continuously with calcium chloride as salting-out agent. Moreover, the experiments confirmed the reliability of the mathematical model of the process. Further experiments are in progress with the aim of utilizing a mixture of salts which can be fed from the bottom of the dehydration section back to the fermentor, so that the salt regeneration stage can be reduced.     

Potentials of pervaporation to assist VOCs’ recovery by liquid absorption

Gas treatment by liquid absorption is a well-known process to remove volatile organic compounds (VOCs) from industrial waste gases. Usually the liquid is an organic solvent of high boiling point; however, after VOCs’ absorption it must be regenerated for the possible reuse and this step is classically achieved by heating the liquid. The paper presents the work directed to investigate an alternative regeneration step based on a liquid-vapour membrane separation, i.e. pervaporation. Because most of the energy required in pervaporation processes is consumed to remove the minor component from the initial mixture by selective permeation through the membrane, one can expect a significant energy cut in the operational costs linked to the regeneration of the liquid if the pervaporation step can substitute the heating one. The results reported here show that the technological possibility to use pervaporation is first governed by the stability of the membrane in the absorption liquid. The viability of the overall process is actually controlled by the mutual affinity between the VOCs, the solvent phase and the polymeric material. As a matter of fact, whereas VOCs have to exhibit strong affinities to both the solvent and the membrane material, the polymer has to be well resistant and even repellent to the solvent to avoid the possible sorption in the membrane that would drastically depress the pervaporation efficiency. In other words the membrane transport properties must be specific for the VOCs. This goal was reached following several experimental approaches, going from membrane modifications to the selection of suitable heavy protic solvents. Hence it has been shown for the case of dichloromethane (DCM) that low molecular weights polyalcohols (e.g. glycols) appeared to be suitable media to allow in particular the specific transport of DCM. On the other hand, polydimethylsiloxane (PDMS) based membranes were selected for their stability in these polyglycols and for their marked affinity for DCM. The simulation of the hybrid gas treatment process at pilot-scale was also achieved by a simple model relying on experimental data for both vapour liquid equilibria and permeation flux. A simple comparison of the energy needed to regenerate the heavy solvent by each possible step has also been made.     

Modelling the performance of membrane nanofiltration—recovery of a high-value product from a process waste stream

For traditional separation processes there are widely available process design methodologies for scale-up and optimization. However, there is an increasing need for such a rational approach to membrane separation processes, identifying at an early stage operating limits and process options. Such predictive models will reduce development risk and time, thus promoting the wider use of membrane technology in process industries such as pharmaceutical manufacture. Design methods exist that have been verified experimentally at the laboratory scale for simple aqueous solutions. There is now a need for the application of the existing theoretical and experimental methods to separations of real industrial interest.In this paper, we demonstrate this philosophy by describing the rationale for modelling the performance of membrane nanofiltration (NF) used in the recovery of sodium cefuroxime, an industrially important cephalosporin antibiotic having activity against most gram-positive cocci. Sodium cefuroxime is produced in a multi-stage biotransformation process with final purification achieved by low-temperature crystallization with excess quantities of sodium lactate. The efficiency of the crystallization process is not 100% and cefuroxime is lost in the waste stream from the crystallization units. Traditionally, this waste stream has been sent for industrial disposal as the concentrations of sodium cefuroxime are too low for normal separation processes to recover.A systematic study of three commercially available membranes indicated that the Desal-5-DK membrane was most suitable for the recovery process. Excellent agreement between the experimental findings and model predictions was observed for batch NF and a membrane charge isotherm was developed for use in process modelling. The full-scale recovery process was modelled theoretically and NF proved more than adequate for the separation required. An estimate of the industrial scale process operating constraints was made and the NF process was considered as a favourable modification to existing plants.     

Biochemical basis of free and immobilised enzyme applications in industry,analysis, synthesis and therapy

Biotechnological use of enzymes has been started with cheap enzymes in soluble form, which were chosen from those that do not require the expense of added cofactors. These simple uses have been mainly in food industry applications, often for hydrolytic purposes in order to improve a process or product. Purified enzymes are finding application in analysis, including immunoassay, stereospecific synthesis and in therapy. In these cases, however, much more enzymological knowledge is needed to understand and control the use of the soluble or immobilised enzyme form. It is the appreciation of enzyme structure-mechanism relationships that is essential to progress. This, and the control of enzyme stability, as determined by changes in protein conformation and aggregation, is of the greatest importance for the ultimate goal of designing new and better enzymes and enzyme analogues.     

Membrane/sorption-enhanced methanol synthesis process: Dynamic simulation and optimization

In this study, a dynamic mathematical model of a Membrane-Gas-Flowing Solids-Fixed Bed Reactor (Membrane-GFSFBR) with in-situ water adsorption in the presence of catalyst deactivation is proposed for methanol synthesis. The novel reactor consists of water adsorbent and hydrogen-permselective Pd-Ag membrane. In this configuration feed gas and flowing adsorbents are both fed into the outer tube of the reactor. Contact of gas and fine solids particles inside packed bed results in selective adsorption of water from methanol synthesis which leads to higher methanol production rate. Afterwards, the high pressure product is recycled to the inner tube of the reactor and hydrogen permeates to the outer tube which shifts the reaction towards more methanol production. Dynamic simulation result reveals that simultaneous application of water adsorbent and hydrogen permeation in methanol synthesis process contributes to a significant enhancement in methanol production. The notable advantage of Membrane-GFSFBR is the continuous adsorbent regeneration during the process. Moreover, a theoretical investigation has been performed to evaluate the optimal operating conditions and to maximize the methanol production in Membrane-GFSFBR using differential evolution (DE) algorithm as a robust method. The obtained optimization result shows there are optimum values of inlet temperatures of gas phase, flowing solids phase, and shell side under which the highest methanol production can be achieved.     

Die Volume‐of‐Fluid‐Methode,ein Verfahren zur Simulation von Zweiphasenströmung

The computational fluid dynamics has gained a growing importance in the last decades. This has been achieved, on the one hand, through the continuously increasing speed of computers, on the other hand, through the development of mathematical‐physical models and numerical algorithms that allow a reality‐close simulation of complex flow processes. In this work, the volume of fluid method is used to simulate a two‐phase flow in a tube. The effects of the contact angle, the temperature and the mass flow of the gas phase on the form of the liquid phase are investigated.     

Metabolic engineering of 2‐pentanone synthesis in Escherichia coli

Expanding the chemical diversity of microbial fermentation products enables green production of fuel, chemicals, and pharmaceuticals. In recent years, coenzyme A (CoA) dependent chain elongation, resembling the reversed β‐oxidation pathway, has attracted interest for its use in producing higher alcohols, fatty acids, and polyhydroxyalkanoate. To expand the chemical diversity of this pathway, we metabolically engineered Escherichia coli to produce 2‐pentanone, which is not a natural fermentation product of E. coli. We describe the first demonstration of 2‐pentanone synthesis in E. coli by coupling the CoA‐dependent chain elongation with the acetone production pathway. By bioprospecting for enzymes capable of efficient hydrolysis of 3‐keto‐hexanoyl‐CoA, production of 2‐pentanone increased 20 fold, reaching a titer of 240 mg/L. © 2013 American Institute of Chemical Engineers AIChE J, 59: 3167–3175, 2013     

Stofftrennung mit überkritischen Gasen (Gasextraktion)

Mass separation with supercritical gases (gas extraction) . The solvent power of dense gases is considered with ongoing interest for use in technical processes. A great number of gaseous solvents are available, especially if solvent mixtures are included. These solvents can be used in one-stage or multiple-stage processes, running batchwise or continuously in countercurrent process. Design the equipment and simulation of the process requires correlation of the underlying phase equilibria. Remarkable progress has been achieved in this field. In some cases data on mass transfer have also been published. Several companies supply turnkey plants or specialized equipment from laboratory to pilot scale. Commercial plants are used extracting natural products and mineral oil residue processing.     

生物技术在手性药物合成中的应用进展

药物分子的立体化学决定了其生物活性,手性已成为药物研究的一个关键因素,生物技术在手性药物合成中具有重要意义,利用酶催化的相关性质,通过酶拆分外消旋体、酶法不对称合成等方法合成手性药物,采用定向进化技术、酶分子修饰、辅酶再生等方法对手性药物合成方法进行改进,该文对近些年来生物技术在手性药物合成中的应用情况进行了综述。     

Several Polyphosphate Kinase 2 Enzymes Catalyse the Production of Adenosine 5′-Polyphosphates

Polyphosphate kinases (PPKs) are involved in many metabolic processes; enzymes of the second family (PPK2) are responsible for nucleotide synthesis fuelled by the consumption of inorganic polyphosphate. They catalyse the phosphorylation of nucleotides with various numbers of phosphate residues, such as monophosphates or diphosphates. Hence, these enzymes are promising candidates for cofactor regeneration systems. Besides adenosine 5′-triphosphate, PPK2s also catalyse the synthesis of highly phosphorylated nucleotides in vitro, as shown here for adenosine 5′-tetraphosphate and adenosine 5′-pentaphosphate. These unusually phosphorylated adenosine 5′-polyphosphates add up to 50 % of the whole adenosine nucleotides in the assay. The two new products were chemically synthesised to serve as standards and compared with the two enzymatically produced compounds by high-performance ion chromatography and ³¹P NMR analysis. This study shows that PPK2s are highly suitable for biocatalytic synthesis of different phosphorylated nucleotides.     

Fabrication and performance of a polyethersulfone nanofiltration membrane impregnated with a mesoporous silica–poly(1‐VInylpyrrolidone) nanocomposite

Fouling is a serious problem in the membrane formation process. Adding hydrophilic polymers or inorganic particles into the membrane is an effective way for improving the antifouling performance. However, most of the water‐soluble polymeric additives leach out during the phase inversion process, and the inorganic particles are prone to agglomerate in the membrane, which decreases the antifouling property of the membrane. In this study, poly(1‐vinylpyrrolidone) (PVP) was grafted onto mesoporous silica (MS) nanoparticle surface, and polyethersulfone (PES)/MS–PVP nanocomposite membranes were fabricated by the phase inversion method. MS–PVP dispersed well on the membrane surface, and the hydrophilicity of the PES/MS–PVP membranes increased with increasing content of MS–PVP. PES/MS–PVP membranes exhibited higher water flux than that of the bare PES membrane without any loss in NaCl rejection, and water flux of 25 L/m²h could be achieved by the membrane containing 3% of MS–PVP, which is almost 1.5 times as high as that of bare PES membrane at 0.6 MPa. The protein adsorption onto the membrane surface declined significantly from 49 to 25 mg/cm² when the MS–PVP loading increased from 0% to 3%. POLYM. COMPOS., 38:908–917, 2017. © 2015 Society of Plastics Engineers     

Recent Advances in Lipase-Mediated Preparation of Pharmaceuticals and Their Intermediates

Biocatalysis offers an alternative approach to conventional chemical processes for the production of single-isomer chiral drugs. Lipases are one of the most used enzymes in the synthesis of enantiomerically pure intermediates. The use of this type of enzyme is mainly due to the characteristics of their regio-, chemo- and enantioselectivity in the resolution process of racemates, without the use of cofactors. Moreover, this class of enzymes has generally excellent stability in the presence of organic solvents, facilitating the solubility of the organic substrate to be modified. Further improvements and new applications have been achieved in the syntheses of biologically active compounds catalyzed by lipases. This review critically reports and discusses examples from recent literature (2007 to mid-2015), concerning the synthesis of enantiomerically pure active pharmaceutical ingredients (APIs) and their intermediates in which the key step involves the action of a lipase.     

Properties and applications of supports for enzyme‐mediated transformations in solid phase synthesis

With the increasing interest in automated synthesis and screening protocols, solid supported chemistry and biochemistry have become attractive technologies. Furthermore, the use of enzymes in solid phase synthesis has opened the route to selective and mild processes. The efficiency of enzymes in transforming substrates that are bound on solid supports is strictly related to the availability of polymers endowed with specific properties, above all permeability to enzymes. This review describes how the recent developments of this rapidly evolving area have made possible novel challenging applications of enzymes in solid phase synthesis. Copyright © 2006 Society of Chemical Industry     

双极膜电渗析技术的研究进展

双极膜电渗析技术(BMED)是利用直流电场作用下双极膜界面层内发生水解离生成H+和OH-这一电化学特性,通过将双极膜与阴、阳离子交换膜适当组合,可实现不同的特种分离功能。与传统工艺相比,BMED具有高效节能、环境友好、操作便捷等突出技术优势。本文介绍了3种不同的BMED工作模型以及BMED在有机酸生产、水除盐、蛋白分离、超纯水制备等领域的最新研究进展,对BMED技术的进一步研究与发展进行了展望。     

Plasma-chemical synthesis and regeneration of catalysts for reforming natural gas

This study describes a pioneering investigation of plasma-chemical synthesis (PCS) and/or regeneration of natural gas-reforming catalysts under the conditions of electric arc, low temperature plasma (LTP), as a function of plasma-chemical process (PCP) parameters and plasma-chemical reactor (PCR) type (with “cold walls” or “warm walls”). Based on the model calculations, a plasma-chemical installation was designed, built, and used to study the processes of catalyst preparation and regeneration of spent, deactivated catalysts for natural gas-reforming.

Plasma-chemically synthesized and/or regenerated samples were analyzed by means of complex physical-chemical, X-ray pattern structural, and electron-microscopic analyses. And the dynamics and kinetics of active surface formation by reduction of catalysts were studied.

A temperature range of 2000–3000 K has been established as optimal for synthesizing samples with maximum dispersion, producing a reduction rate 2–4 times faster than industrial analogues. Samples with high catalytic activity (CH₄ conversion rate, catalyst performance, catalyst efficiency) and thermal stability were obtained.

Thus, it has been found that LTP can be successfully used for catalyst synthesis and regeneration.