Enzyme capturing and concentration with mixed matrix membrane adsorbers

Organic-Solvent-Resistant Polyimide/Hydroxyapatite Mixed Matrix Membranes for Lysozyme Adsorption

This work reports new mixed matrix membranes (MMMs) for the adsorption of enzymes from organic solvents. In this work, polyimide/hydroxyapatite (PI/HAP) MMMs were prepared via phase inversion method and further crosslinked with 3-aminopropyl triethoxysilane (APTES). The chemical and structural stability of the crosslinked PI/HAP MMMs were improved and applied for lysozyme (LZ) adsorption in organic solvent. PI/HAP MMMs were crosslinked by changing the 3-aminopropyltriethoxysilane (APTES) concentration and crosslinking time. The optimal APTES crosslinking condition for PI/HAP MMMs is 6% of concentration for 8 h. The LZ adsorption performance was studied by changing solvent types. PI/HAP MMMs possessed a high LZ adsorption in organic-solvent-aqueous solutions, and the LZ adsorption capacity reached 34.1 mg/g. The MMMs had a high desorption capacity and recovery ability. The MMMs maintained 60% of their adsorption capacity and 58% of their desorption at the fourth cycle of adsorption and desorption. The MMMs provided a new technology for the purification and separation of enzymes or proteins by MMMs in organic solvents.

Membrane Chromatography and Fractionation of Proteins from Whey—A Review

Membrane chromatography (MC) is an emerging bioseparation technology combining the principles of membrane filtration and chromatography. In this process, one type of molecule is adsorbed in the stationary phase, whereas the other type of molecule is passed through the membrane pores without affecting the adsorbed molecule. In subsequent the step, the adsorbed molecule is recovered by an elution buffer with a unique ionic strength and pH. Functionalized microfiltration membranes are usually used in radial flow, axial flow, and lateral flow membrane modules in MC systems. In the MC process, the transport of a solute to a stationary phase is mainly achieved through convection and minimum pore diffusion. Therefore, mass transfer resistance and pressure drop become insignificant. Other characteristics of MC systems are a minimum clogging tendency in the stationary phase, the capability of operating with a high mobile phase flow rate, and the disposable (short term) application of stationary phase. The development and application of MC systems for the fractionation of individual proteins from whey for investigation and industrial-scale production are promising. A significant income from individual whey proteins together with the marketing of dairy foods may provide a new commercial outlook in dairy industry. In this review, information about the development of a MC system and its applications for the fractionation of individual protein from whey are presented in comprehensive manner.

Clinoptilolite-based mixed matrix membranes for the selective recovery of potassium and ammonium

A clinoptilolite-based mixed matrix membrane (MMM) was developed and studied for the selective recovery of ammonium and potassium. Adsorption of sodium (Na(+)), potassium (K(+)) and ammonium (NH4(+)) was investigated with single salt and equimolar salt solution under static and dynamic conditions. Furthermore, the adsorption capacity of clinoptilolite was investigated when embedded in the MMM and in clay form. Two conditioning methods were compared: HCl and NaCl. Conditioned clinoptilolite with NaCl gave higher static adsorption capacities than with HCl which alters the chemical structure of clinoptilolite. The adsorption of Na(+) was not detected in the static adsorption experiments and results showed that Na(+) adsorbed during the conditioning process it was exchanged by K(+) and NH4(+).The clinoptilolite embedded in MMM reduced the porosity of the MMM so the highest adsorption capacity was reached when the amount of polymer was the lowest: 30 wt% polymer and 70 wt% clinoptilolite. The application of MMM in a dead-end filtration cell (dynamic adsorption) resulted in higher adsorption capacities compared to static conditions and comparable results between synthetic solutions and diluted urine samples. This indicates that MMM is a suitable method for the recovery of K(+) and NH4(+) directly from a diluted urine matrix. The desorption (recovery) of K(+) and NH4(+) from MMM was higher using water at 60 °C than using an acidic treatment.

Adsorption of protein onto double layer mixed matrix membranes

This work proposed a novel approach for protein purification by using double layer mixed matrix membranes (MMMs). The double layer MMMs consisting of an active support and separating layer were prepared by co-casting two polymer solutions onto a glass plate. The active support layer consisted of nano hydroxyapatite (HAP) particles embedded in macroporous polyether sulfone (PES) and the separating layer was particle free PES membrane. The influence of separating layer with different PES content on membrane morphology was studied. The double layer MMMs were further characterized concerning permeability and adsorption capacity. The double layer MMMs showed purification of protein via diffusion as well as adsorption. The bovine serum albumin (BSA) was used as a model protein. The properties and structures of double layer MMMs prepared by immersion phase separation process were characterized by pure water flux, BSA adsorption and scanning electron microscopy (SEM).

A novel approach for blood purification: mixed-matrix membranes combining diffusion and adsorption in one step

Hemodialysis is a commonly used blood purification technique in patients requiring kidney replacement therapy. Sorbents could increase uremic retention solute removal efficiency but, because of poor biocompatibility, their use is often limited to the treatment of patients with acute poisoning. This paper proposes a novel membrane concept for combining diffusion and adsorption of uremic retention solutes in one step: the so-called mixed-matrix membrane (MMM). In this concept, adsorptive particles are incorporated in a macro-porous membrane layer whereas an extra particle-free membrane layer is introduced on the blood-contacting side of the membrane to improve hemocompatibility and prevent particle release. These dual-layer mixed-matrix membranes have high clean-water permeance and high creatinine adsorption from creatinine model solutions. In human plasma, the removal of creatinine and of the protein-bound solute para-aminohippuric acid (PAH) by single and dual-layer membranes is in agreement with the removal achieved by the activated carbon particles alone, showing that under these experimental conditions the accessibility of the particles in the MMM is excellent. This study proves that the combination of diffusion and adsorption in a single step is possible and paves the way for the development of more efficient blood purification devices, excellently combining the advantages of both techniques.

Functionalized lipid nanoparticles-cellophane hybrid films for molecular delivery: preparation, physicochemical characterization, and stability

Lipid nanoparticles functionalized with the sunscreen 2,4-dihydroxybenzophenone (FLNPs) have been prepared by the ultrasound method and embedded in highly hydrophilic cellophane supports (regenerated cellulose, RC), creating biocompatible hybrid films (RC-FLNPs samples). The morphology of the FLNPs was studied with transmission microscopy, whereas the surface and interior chemical composition was analyzed by micro-Raman spectroscopy. RC-FLNPs hybrid films were prepared from the immersion of two cellophane supports with different thicknesses and water uptake properties (RC-3 and RC-6) in an aqueous dispersion of FLNPs. The structure of this hybrid material was visualized with bright-field microscopy, which clearly showed the inclusion of the FLNPs in the cellophane matrix. The stability of the RC-FLNPs films with respect to both aqueous environments and time was demonstrated by NaCl diffusion measurements. The reduction in the diffusion coefficient through the nanoparticle-modified films compared with the original supports confirms the presence of nanoparticles for concentration gradients of up to 0.4 M (osmotic pressure around 10 bar), indicating the stability of the hybrid hydrophilic material, even in aqueous environments and under matter flow conditions for a period of 21 days.

Membrane-based techniques for the separation and purification of proteins: an overview

Membrane processes are increasingly reported for various applications in both upstream and downstream technology, such as microfiltration, ultrafiltration, emerging processes as membrane chromatography, high performance tangential flow filtration and electrophoretic membrane contactor. Membrane-based processes are playing critical role in the field of separation/purification of biotechnological products. Membranes became an integral part of biotechnology and improvements in membrane technology are now focused on high resolution of bioproduct. In bioseparation, applications of membrane technologies include protein production/purification, protein-virus separation. This manuscript provides an overview of recent developments and published literature in membrane technology, focusing on special characteristics of the membranes and membrane-based processes that are now used for the production and purification of proteins.

Thiol Functionalized Silica-Mixed Matrix Membranes for Silver Capture from Aqueous Solutions: Experimental Results and Modeling

The study deals with an aqueous phase application of Mixed Matrix Membranes (MMMs) for silver ion (Ag(+)) capture. Silica particles were functionalized with 3-mercaptopropyltrimethoxy silane (MPTMS) to introduce free thiol (-SH) groups on the surface. The particles were used as the dispersed phase in the polysulfone or cellulose acetate polymer matrix. The membranes were prepared by the phase inversion method to create more open and interconnected porous structures suitable for liquid phase applications. The effects of the silica properties such as particle size, specific surface area, and porous/nonporous morphology on the silver ion capture capacity were studied. It was demonstrated that the membranes are capable of selectively capturing silver from a solution containing significant concentrations of other metal ions like Ca(2+). The membranes were studied to quantify the dynamic capacity for silver ion capture and its dependence on residence time through the adjustment of transmembrane pressure. The thiol-Ag(+) interaction was quantified with Quartz Crystal Microbalance in a continuous flow mode experiment and the observations were compared with the membrane results. One dimensional unsteady state model with overall volumetric mass transfer coefficient was developed and solved to predict the silver concentration in the liquid phase and the solid silica phase along the membrane thickness at varying time. The breakthrough data predicted using the model is comparable with the experimental observations. The study demonstrates successful application of the functionalized silica-mixed matrix membranes for selective aqueous phase Ag(+) capture with high capacity at low transmembrane pressures. The technique can be easily extended to other applications by altering the functionalized groups on the silica particles.

Fast determination of conditions for maximum dynamic capacity in cation-exchange chromatography of human monoclonal antibodies

Dynamic binding capacity (DBC) measurements of cation-exchange resins were performed with two human monoclonal antibodies. DBC showed a pH dependent maximum, which was shifted to lower pH values with increasing buffer concentrations and increasing salting-out effect of the buffer anion according to the Hofmeister series. As this downshift correlates well with zeta potential values, a measurement of the latter allows the determination of the pH value for maximum DBC under a given set of conditions. Thus, the use of zeta potential values can accelerate the purification process development and helps to understand the protein adsorption mechanism.

Membrane engineering in biotechnology: quo vamus?

Membranes are essential to a range of applications, including the production of potable water, energy generation, tissue repair, pharmaceutical production, food packaging, and the separations needed for the manufacture of chemicals, electronics and a range of other products. Therefore, they are considered to be "dominant technologies" by governments and industry in several prominent countries--for example, USA, Japan and China. When combined with catalysts, membranes are at the basis of life, and membrane-based biomimetism is a key tool to obtain better quality products and environmentally friendly developments for our societies. Biology has a main part in this global landscape because it simultaneously provides the "model" (with natural biological membranes) and represents a considerable field of applications for new artificial membranes (biotreatments, bioconversions and artificial organs). In this article, our objective is to open up this enthralling area and to give our views about the future of membranes in biotechnology.