双水相萃取技术研究新进展

介绍了双水相萃取技术(ATPE)在生物工程下游工程中的应用现状,综述了近年来ATPE相关研究的进展。为了提高ATPE的选择性和分离效率,不但发展了热分离聚合物体系和表面活性剂混合体系等新型双水相系统(ATPS),而且在组成传统ATPS的聚合物上耦联亲和配基的亲和ATPS也得到发展。与物理场作用、其他分离技术和生物过程的集成克服了单一ATPE的某些不足,是ATPE的发展方向。常规萃取设备和连续化操作技术在ATPE中的应用标志着其工业化日趋成熟,但建立溶质在ATPS中分配的热力学模型和相关理论有待进一步完善。     

Production of polyhydroxyalkanoates: the future green materials of choice

Polyhydroxyalkanoates (PHAs) have recently been the focus of attention as a biodegradable and biocompatible substitute for conventional non degradable plastics. The cost of large‐scale production of these polymers has inhibited its widespread use. Thus, economical, large‐scale production of PHAs is currently being studied intensively. Various bacterial strains, either wild‐type or recombinant have been utilized with a wide spectrum of utilizable carbon sources. New fermentation strategies have been developed for the efficient production of PHAs at high concentration and productivity. With the current advances, PHAs can now be produced to a concentration of 80 g L^?1 with productivities greater than 4 g PHA L^?1 h^?1. These advances will further lower the production cost of PHAs and allow this family of polymers to become a leading biodegradable polymer in the near future. This review describes the properties of PHAs, their uses, the various attempts towards the production of PHAs, focusing on the utilization of cheap substrates and the development of different fermentation strategies for the production of these polymers, an essential step forward towards their widespread use. Copyright © 2010 Society of Chemical Industry     

聚羟基烷酸酯的研究进展

微生物发酵合成的聚羟基烷酸酯(PHAs)作为最具有发展潜力的新型生物高分子材料之一,备受关注。本文介绍了近几年来有关PHAs的生物合成、分离纯化、性能改进、生产与应用现状等方面研究的最新进展,探讨了这一领域未来可能的发展热点和动向。     

Graphene oxide versus functionalized carbon nanotubes as a reinforcing agent in a PMMA/HA bone cement

Graphene oxide (GO) and functionalized carbon nanotubes (f-CNTs) (each in the concentration range of 0.01-1.00 wt/wt%) were investigated as the reinforcing agent in a poly(methyl methacrylate) (PMMA)/hydroxyapatite (HA) bone cement. Mixed results were obtained for the changes in the mechanical properties determined (storage modulus, bending strength, and elastic modulus) for the reinforced cement relative to the unreinforced counterpart; that is, some property changes were increased while others were decreased. We postulate that this outcome is a consequence of the fact that each of the nanofillers hampered the polymerization process in the cement; specifically, the nanofiller acts as a scavenger of the radicals produced during polymerization reaction due to the delocalized π-bonds. Results obtained from the chemical structure and polymer chain size distribution determined, respectively, by nuclear magnetic resonance and size exclusion chromatography analysis, on the polymer extracted from the specimens support the postulated mechanism. Furthermore, in the case of the 0.5 wt/wt% GO-reinforced cement, we showed that when the concentration of the radical species in the PMMA bone cement was doubled, mechanical properties markedly improved (relative to the value in the unreinforced cement), suggesting suppression of the aforementioned scavenger activity.     

Purification of biomolecules combining ATPS and membrane chromatography

Upstream processes for production of therapeutic proteins have been innovated and fermentation processes have been adopted for the use of recombinant microorganisms with high expression, but the downstream process is still the bottleneck in the biotechnological manufacturing process. A combined process consisting of aqueous two phase extraction (ATPE) and membrane chromatography is suggested to debottleneck downstream processing. ATPE has a large capacity, but the yield of the target product is from 74% to 97%. For this reason the product of ATPE waste stream is captured by membrane chromatography. In this work the binding capacity for the protein on protein A, ion exchange and hydrophobic exchange membrane chromatography was investigated experimentally with different concentration of polyethylene glycol (PEG), salt and protein. Protein A membrane was loaded with solutions resembling waste streams of ATPE for purifying IgG. For ion exchange and hydrophobic interaction membrane chromatography, the membrane was loaded with bovine serum albumin (BSA). PEG shows no significant effect on stability and capacity of membrane process. Even for small amount of BSA/IgG and high salt concentrations membrane adsorption is applicable. In this work it is demonstrated experimentally that a total product recovery of 99.9% for the purification of monoclonal antibody is possible.     

Integration of Aqueous Two‐Phase Extraction into Downstream Processing

Aqueous two‐phase extraction (ATPE) is increasingly considered to be a feasible unit operation, e.g., for the capture of monoclonal antibodies or recombinant proteins. So far, knowledge on the applicability of ATPE in antibody processes has been collected mostly in lab‐scale. In contrast, approaches for the integration of ATPE into a downstream process are investigated. A complete process sequence including extraction, washing, ultrafiltration, and ion‐exchange chromatography is discussed and suggested for antibody purification. Excellent antibody purities can be achieved. Additionally, a model is applied that allows early‐on prediction of a multistage ATPE with high prediction accuracy. Finally, an economic evaluation between ATPE and Protein A chromatography is performed, reaching up to five‐fold cost‐saving factors.     

Development of novel conducting composites of linseed‐oil‐based poly(urethane amide) with nanostructured poly(1‐naphthylamine)

Novel conducting polymer composites of linseed‐oil‐based poly(urethane amide) (LPUA) were synthesized using nanostructured poly(1‐naphthylamine) (PNA). The combination of the electrically conducting PNA with LPUA was accomplished through different weight percent loadings (0.5–2.5 wt%) of the conducting polymer. The particle size of the nanocomposite was determined using transmission electron microscopy and was found to be in the range 17–27 nm. Intermolecular hydrogen bonding between the two polymers and formation of urea linkages were confirmed by Fourier transform infrared spectroscopy. The electrical conductivity of the nanostructured conducting composites at 2.5 wt% loading was found to be comparable to that reported for polyaniline (PANI)/polyurethane at 30 wt% loading of PANI. This shows the superior properties of PNA and its potential for application in anti‐static as well as corrosion‐protective coatings. The present method of formulation of composites using an oil‐based polymer matrix is useful and economically feasible in the sense that a great variety of oil‐based polymer matrices can be used to form composites that are ecologically safe and exhibit properties similar to commercial polymers. Copyright © 2007 Society of Chemical Industry     

Separation of Bromelain by Aqueous Two Phase Flotation

Aqueous two phase flotation (ATPF) system of polyethylene glycol (PEG) and potassium phosphate is studied for the separation and partial purification of bromelain from the pineapple fruit (Annanus comosus L. Merryl). The effect of PEG molecular weight (1500–20000), concentration of phase forming components (PEG 12–18% w/w and potassium phosphate 14–20% w/w), system pH, nitrogen flow rate, and flotation time were studied and optimum conditions for ATPF were obtained. At optimum conditions of the system, i.e., 14% w/w PEG 1500, 18% w/w potassium phosphate, 80 mL/min of nitrogen flow rate and pH 7, maximum yield of 91.47% and purification fold of 4.26 were obtained. ATPF was found to be an effective technique for the purification of bromelain from pineapple fruit with higher extraction yield and purification fold as compared to aqueous two phase extraction (ATPE).     

A simple method for purification of bromelain in a thermosensitive triblock copolymer-based protection system and recycling of phase components

In the work, we chose stem bromelain as a model to investigate the storage and purification of bromelain from pineapple peel. Extraction of bromelain from pineapple peel using a two-stage aqueous two-phase extraction system composed of a thermoseparating copolymer EOPOEO and K₂HPO₄. Bromelain predominantly partitioned to the EOPOEO-rich phase and then re-extract to the top dilute phase. The recovery of enzyme activity (68.6%) and purification factor (6.53) were determined under optimum conditions. The EOPOEO-rich phase and salt were recycled, and the recovery of enzyme activity could reach up to 60%. This method has been proved to obtain highly purified and stable bromelain.     

Performance of talc/ethylene-octene copolymer/polypropylene blends

Polypropylene-based compounds are increasingly attractive because of low cost, processability, and good balance of properties. In recent years, metallocene ethylene-octene copolymers have started displacing EPR and EPDM as an impact modifier for PP. This study examines the effect of compounding conditions and composition on the properties of talc/ethylene-octene copolymer/PP compounds. The mechanical properties of the compounds were not significantly affected by the mixing conditions on a laboratory twin screw extruder. The use of 30 wt% of talc provided a twofold increase in tensile modulus compared with pure PP. Impact resistance of filled and unfilled compounds was found to increase rapidly once the copolymer concentration reached around 20 wt% based on the polymer phase. Modulus and tensile strength decreased linearly with copolymer concentration. Four different commercial maleic anhydride-grafted PPs were tested as interfacial modifiers. In the best cases, a slight tensile strength increase was observed when using between 2 and 10 wt% of modified PP.     

Enhancing Oil Recovery by Low Concentration of Alkylaryl Sulfonate Surfactant without Ultralow Interfacial Tension

Surfactant flooding plays a critical role in chemically enhanced oil recovery over the last half century, with the widely accepted mechanism of ultralow interfacial tension (IFT) by forming middle-phase microemulsions with high concentration of a lead surfactant and a cosurfactant. However, it is found practically from field trials that high oil recovery efficiency can be obtained from low concentration surfactant flooding without forming microemulsions, and the principle behind has not been clearly unraveled yet. Here the solubilization of paraffin oil by the micelles formed with a commercial enhanced oil recovery surfactant, raw naphthenic arylsulfonates (NAS), was investigated using ultraviolet-visible (UV–Vis) spectroscopy, dynamic light scattering (DLS), and transmission electron microscopy (TEM). It is found that paraffin oil can be well solubilized inside the NAS micelles, and mainly localized in the hydrophobic core of the micelles. The solubilization capacity of NAS micelles increases with increasing its concentration, and the size of micelles increases, but morphology of the micelles remains spherical with increasing the amount of paraffin oil, along with an appearance transition from transparent to opaque until the maximum solubilization capacity is reached. Core flooding results with crude oil indicate that in the presence of 0.24 wt.% polymer, addition of 0.1, 0.2, 0.5, and 1.0 wt.% NAS can get oil recovery factor of 24.1%, 27.0%, 30.5%, and 38.3%, which increases linearly with increasing NAS concentration though with the interfacial tension values only in the magnitude of 10⁻² mN m⁻¹ level. These findings prove preliminarily micellar solubilization can help increasing oil recovery efficiency even without ultralow IFT.     

Polyhydroxyalkanoates,a family of natural polymers,and their applications in drug delivery

Polyhydroxyalkanoates (PHAs) are natural biopolymers produced by various microorganisms as a reserve of carbon and energy. PHA synthesis generally occurs during fermentation under nutrient limiting conditions with excess carbon. There are two main types of PHAs, short chain length PHAs (scl‐PHAs) and medium chain length PHAs (mcl‐PHAs). The mechanical and thermal properties of PHAs depend mainly on the number of carbons in the monomer unit and its molecular weight. PHAs are promising materials for biomedical applications because they are biodegradable, non‐toxic and biocompatible. The large range of PHAs, along with their varying physical properties and high biocompatibility, make them highly attractive biomaterials for use in drug delivery. They can be used to produce tablets, micro‐ and nanoparticles as well as drug eluting scaffolds. A large range of different PHAs have been explored and the results obtained suggest that PHAs are excellent candidates for controlled and targeted drug delivery systems. © 2015 Society of Chemical Industry     

Photocatalytic degradation and heat reflectance recovery of waterborne acrylic polymer/ZnO nanocomposite coating

This work aims to clarify the photocatalytic degradation mechanism and heat reflectance recovery performance of waterborne acrylic polymer/ZnO nanocomposite coating. To fabricate the nanocomposite coating, ZnO nanoparticles (nano-ZnO) were dispersed into acrylic polymer matrix at the various concentrations from 1 to 6% (by total weight of resin solids). The photocatalytic degradation of nanocomposite coating under ultraviolet (UV) light irradiation has been investigated by monitoring its weight loss and chemical/microstructural/morphological changes. As the topcoat layer, its heat reflectance recovery has been evaluated under UV/condensation exposure by using an artificial dirty mixture of 85 wt% nanoclay, 10 wt% silica particles (1–5 μm), 1 wt% carbon black, and 2 wt% engine oil. After 108-cycle UV/condensation exposure, infrared spectra and weight loss analysis indicated that the maximal degradation for nanocomposite coating is observed at 1 wt% nano-ZnO. On the other hand, after 96 hr of UV light exposure, the nanocomposite coating with1 wt% nano-ZnO could restore effectively the reflective index of solar-heat reflectance coating (from 58.45 to 80.78%). Finally, the photodegradation mechanism of this waterborne acrylic polymer coating has been proposed as the UV-induced formation of CC CO conjugated double bonds. As a result, its self-cleaning phenomenon can be achieved as the recovery of heat reflectance.     

Structure–property relationship of modified polypropylene–polycaproamide fiber

The effect of the addition of polyamide on the structure and properties of polypropylene fiber has been studied. Although a good fiber is obtained with a composition containing only a very low concentration of polycaproamide in polypropylene, the increase in polyamide content decreases the drawing strength of the mixed polymer melt due to sudden lowering of melt viscosity and strength. The poor melt strength of the studied polymer mixture is attributed to increased heterogeneity induced in the system with increased concentration of polyamide. Use of an effective interphase modifier, maleic anhydride-grafted polypropylene, however, was found to improve fiber properties of the studied polymer mixtures even with a very high concentration of polyamide as the dispersed phase. Thus, addition of a 1–4 wt % interphase modifier facilitates the formation of good fiber even with 30 wt % polycaproamide in the blend. This improvement is attributed to the improved dispersity of polyamide in the polypropylene matrix as well as improved phase compatibility due to the formation of a chemically modified polyamide during melt extrusion in the presence of maleic anhydride-grafted polypropylene.     

Fluorescent detection of heparin by a cationic conjugated polyfluorene probe containing aggregation-induced emission units

A novel conjugated cationic polyfluorene containing aminated tetraphenylethene (ATPE) unit is developed as a sensitive and selective fluorescence probe for heparin detection based on the combination of aggregation-induced emissive property of the ATPE units and the FRET process from the blue-emissive polyfluorene segments to the yellow-emissive ATPE units. The addition of anionic heparin will lead to the formation of heparin/polymer complexes, and turn on the aggregation-induced yellow emission of the ATPE units. A good linear relationship is found between the yellow emission intensity of the ATPE units and the heparin concentrations with a limit of detection of 30 nM in aqueous buffer.     

In vitro production of polyhydroxyalkanoates: achievements and applications

The mechanisms of polyhydroxyalkanoate (PHA) production have been studied for over half a century. However, despite numerous improvements in the control of monomer composition, genetically‐engineered host organisms, fermentation strategies and polymer recovery processes they remain uncompetitive compared with petrochemical plastics. Recently, interest has developed in the enzyme‐catalysed production of PHAs in vitro. This has allowed the study of enzyme kinetics and properties, and represents another strategy for the economic production of PHAs on the industrial scale. It also presents an opportunity to coat other materials in thin films of PHA so as to modify the surface properties. In vitro production offers advantages over in vivo methods as it enables greater control over monomer composition and molecular weight, does not require a biomass‐accumulation phase, simplifies downstream processing and can utilise a wider range of monomeric subunits. Copyright © 2009 Society of Chemical Industry     

RETRACTED ARTICLE: Towards understanding polyhydroxyalkanoates and their use

It is fact that Polymers and their products have changed the face of the world in all the field of the technology. They are the future of the coming up generation of the research of the world. But this is also fact that these synthetic non biodegradable polymers have created a tough situation for the living being for a healthy life. Polyhydroxyalkanoates are polyesters produced by bacteria as intracellular storage materials in response to a variety of nutritional and environmental conditions, such as nitrogen limitation Polyhydroxyalkanoates (PHAs) are gaining increasing attention in the biodegradable polymer market due to their promising properties such as high biodegradability in different environments, not just in composting plants, and processing versatility. Indeed among biopolymers, these biogenic polyesters represent a potential sustainable replacement for fossil fuel-based thermoplastics. Most commercially available PHAs are obtained with pure microbial cultures grown on renewable feedstocks (i.e.glucose) under sterile conditions but recent research studies focus on the use of wastes as growth media.PHA can be extracted from the bacteria cell and then formulated and processed by extrusion for production of rigid and flexible plastic suitable not just for the most assessed medical applications but also considered for applications including packaging, moulded goods, paper coatings, non-oven fabrics, adhesives, films and performance additives. The present paper reviews the PHAs, their main properties, processing aspects, commercially available ones, as well as limitations and related improvements being researched,with specific focus on potential applications of PHAs in packaging.     

Flowsheet simulation of aqueous two‐phase extraction systems for protein purification

BACKGROUND: Aqueous two‐phase extraction (ATPE) has many advantages as an efficient, inexpensive large‐scale liquid–liquid extraction technique for protein separation. However, the realization of ATPE as a protein separation technology at industrial scales is rather limited due to the large, multidimensional design space and the paucity of design approaches to predict phase and product behavior in an integrated fashion with overall system performance. This paper describes a framework designed to calculate suitable flowsheets for the extraction of a target protein from a complex protein feed using ATPE. The framework incorporated a routine to set up flowsheets according to target protein partitioning behavior in specific ATPE systems and a calculation of the amounts of phase‐forming components needed to extract the target protein. The thermodynamics of phase formation and partitioning were modeled using Flory‐Huggins theory and calculated using a Gibbs energy difference minimization approach. RESULTS: As a case study, suitable flowsheets to recover phosphofructokinase from a simple model feedstock using poly(ethylene glycol)‐dextran (PEG6000‐DxT500) and poly(ethylene glycol)‐salt (PEG6000‐Na₃PO₄) two‐phase systems were designed and the existence of feasible solutions was demonstrated. The flowsheets were compared in terms of product yield, product purity, phase settling rate and scaled process cost. The effect of the mass flowrates of phase‐forming components on product yield and purity was also determined. CONCLUSION: This framework is proposed as a basis for flowsheet optimization for protein purification using ATPE systems. Copyright © 2010 Society of Chemical Industry     

Preparation of Scratch and Abrasion Resistant Polymeric Nanocomposites by Monomer Grafting onto Nanoparticles, 3. Effect of Filler Particles and Grafting Agents

After modification with different trialkoxysilanes, nano‐sized silica and alumina particles were used as fillers in transparent UV/EB curable acrylates for polymer reinforcement, particularly to attain scratch and abrasion resistant coatings. The acid catalyzed condensation of the organosilanes forms a polysiloxane shell which covers the nanoparticle like a nanocapsule. CP MAS NMR spectroscopy and MALDI‐TOF mass spectrometry proved to be useful for the characterization of the polysiloxane structures. Grafted oligomers with more than 20 monomeric units were observed. Nanoparticles modified by methacroyloxy(propyl)trimethoxysilane and vinyltrimethoxysilane can copolymerize with acrylates. Compared with the pure polymers, these crosslinked polyacrylate nanocomposites, containing up to 35 wt.‐% silica, exhibit markedly improved surface mechanical properties. Promising scratch and abrasion resistance of radiation‐cured nanocomposite materials were also obtained by propyltrimethoxysilane grafting which results in an organophilation of pyrogenic silica. Both colloidal and pyrogenic nano‐sized silica nanopowders were used as fillers in polyacrylate films. The concentration of colloidal SiO₂ in commercial acrylate formulations amounts up to 50 wt.‐%, whereas pyrogenic silica, notwithstanding their surface modification by silanes, results in a thickening effect which limits its content to about 35 wt.‐%. Nevertheless, a comparison showed a distinct improvement in the surface mechanical properties such as haze and diamond microscratch hardness for surface‐modified pyrogenic silica.     

LDPE耐候棚膜专用料2F0.4B的研制与开发

通过光稳定剂的选择及浓度的确定、复配抗氧剂体系的研究，开发生产了低密度聚乙烯耐候棚膜专用料2F0．4B，并对产品进行了性能考核、棚膜大田应用试验，结果表明：2F0．4A－1的力学性能，耐老化性能最佳。适宜作为该专用料的基础树脂； 聚合物受阻胺光稳定剂B的光稳定效果最好；膜厚0．10mm时，光稳定剂B的最小加入量0．20％，膜厚0．08mm时，光稳定剂B的最小加入量0．22％，选择合适的复合抗氧剂体系可以获得良好的抗热氧老化以及抗背板效应；含相同助剂，厚度不同（0．06，0．08，0．11mm)的棚膜老化前期差异不明显，老化后期较薄的膜力学性能衰竭迅速。