Biphasic Membrane Reactor Research Articles

Modeling and simulation of bi‐continuous jammed emulsion membrane reactors for enhanced biphasic enzymatic reactions

AbstractBi‐continuous jammed emulsion (bijel) membrane reactors, integrating simultaneous reaction and separation, offer a promising avenue for enhancing membrane reactor processes. In this study, we present a comprehensive macroscopic‐scale physicochemical model for tubular bijel membrane reactors and a numerical solution strategy for solving the governing partial differential equations. The model captures the co‐continuous network of two immiscible phases stabilized by nanoparticles at the liquid–liquid interface. We present the derivation of model equations and an efficient numerical solution strategy. The model is validated with experimental results from a conventional enzymatic biphasic membrane reactor for oleuropein hydrolysis, already reported in the literature. Simulation results indicate accurate prediction of reactor behavior, highlighting the potential superiority of bijel membrane reactors over current technologies. This research contributes a valuable tool for scale‐up, design, and optimization of bijel membrane reactors, filling a critical gap in this emerging field.

Modeling of a biphasic membrane reactor catalyzed by lipase immobilized in a hydrophilic/hydrophobic composite membrane

A diffusion-reaction model suitable for high enzyme loading density was developed to describe the situation of immobilized lipase in the hydrophilic cellulose acetate (CA)/hydrophobic polytetrafluoroethylene (PTFE) composite membrane. Under this situation, not all the immobilized enzyme was found to be effective, and as such, a utilization coefficient of immobilized lipase was proposed. In this paper, two different reaction systems (racemic ibuprofen ester chiral separation and olive oil hydrolysis) using immobilized lipase in hydrophilic/hydrophobic composite membrane was studied. The former system is reaction controlled and the latter is diffusion controlled. The utilization coefficient of lipase catalyzing the racemic ibuprofen ester was from 83% to 39%, decreasing with the increasing of enzyme loading from 0.3 to 2.1 g m −2. The calculation values were found to be consistent with the experimental data through the utilization coefficient of lipase, which was obtained by the first system to predict the reaction rate of the second one. The effect of substrate concentration and membrane structure on the activity of the immobilized lipase was investigated with this model. We conclude that (1) the effect of substrate concentration is double-edged, (2) utilization coefficient of lipase decreases with the increasing of enzyme loading, (3) composite membranes with thinner and more porosity hydrophobic layer leads to higher reaction rate.

Immobilization of lipase by filtration into a specially designed microstructure in the CA/PTFE composite membrane

A specially designed microstructure in the composite membrane with a porous hydrophobic layer and a relatively dense hydrophilic layer is proposed for lipase immobilization. Firstly, the composite membrane was prepared by coating the cellulose acetate layer with the average pore size of 1.40 nm on the hydrophobic PTFE layer with the average pore size of 76.3 nm. Then, enzymes were absorbed in pores of PTFE layer and deposited on the interface between the two layers by the filtration process. The relatively dense CA layer was used to reject the enzymes controlling the enzyme loading which prevented enzymes from being dissolved into the aqueous phase. The porous PTFE layer supplied a hydrophobic environment and a large specific surface area for the immobilization of lipases which were propitious to the activation of lipase. The activity of immobilized lipase membrane based on hydrolysis of olive oil was assayed in the biphasic membrane reactor and the maximum specific activity (1.20 ± 0.04 μmol-FFA min −1 cm −2) was found to be higher than the value reported in some literature. The kinetic parameters of the immobilized lipases, K m and k max were fitted with the Michaelis–Menten equation. The Thiele modulus ( φ) was used to evaluate the effect of the mass transfer through the membrane on the performance of reaction systems. The optimum enzyme loading (0.020 ± 0.002 mg-protein cm −2) was obtained with the highest activity and without the diffusion-limited. Furthermore, the immobilized lipases retained 80% residual activity after ten hydrolysis cycles. The composite membrane was easily regenerated and lipases immobilized in the regenerated membrane remained a high activity.

Candida rugosa lipase immobilized by a specially designed microstructure in the PVA/PTFE composite membrane

A composite membrane made of a hydrophobic synthetic material, PTFE, and a biocompatible material, PVA, is proposed to immobilize lipase. The structure of this composite membrane is specially designed and includes a porous PTFE layer and an ultrafiltration PVA layer. In the present study, enzymes were absorbed in pores of PTFE layer and deposited on the interface between the two layers by a filtration process. The ultrafiltration PVA layer rejects enzymes to control the enzyme loading and prevents enzymes from being dissolved into the aqueous phase. The porous PTFE layer with micrometer pores supplies a hydrophobic environment for immobilized lipases which is propitious to the activation of lipase. An immobilized lipase membrane was employed in a biphasic membrane reactor (BMR) for the hydrolysis of olive oil. The volumetric reaction rate of the BMR was used to evaluate the catalytic ability of immobilized lipase membrane. The effect of the structure of the PTFE support layer and the PVA layer, the lipase loading density and the BMR stability was investigated, and The maximum reaction rate per unit of membrane area (9.25 μmol/h cm 2) in experimental conditions was found to be higher than the value reported in some literature. The leakage of immobilized lipases was small and did not have a great effect on the catalytic ability when an immobilized lipase membrane was employed in the BMR.

Hydrolysis of olive oil using lipase bonded to modified carbon membrane

AbstractA noninterpenetrating supported carbon membrane was prepared using a resole‐type phenol‐formaldehyde resin as precursor. Amine groups were created on the carbon membrane through nitration using NOx and used to immobilize lipase enzyme by reacting with glutaraldehyde. To maintain high enzyme activity, surface carboxylic groups were modified and the immobilized enzyme on the membrane thus obtained was active even after 3 months of usage. The performance of the biphasic membrane reactor is studied in terms of amount of free fatty acid produced per unit time based on the volume of aqueous phase and the effect of operating variables (pH of aqueous phase solution, solvent used for olive oil, olive oil concentration, and aqueous phase circulation rate) were evaluated. Experiments show that the activity of lipase increases 1.42‐fold upon immobilization. The maximum reaction rate was 3.6‐fold higher, and the base case rate was 1.4‐fold higher than the values reported in the literature for a similar enzyme membrane reactor but with a different membrane. © 2005 American Institute of Chemical Engineers AIChE J, 2006

Optical resolution of racemic 2-hydroxy octanoic acid using biphasic enzyme membrane reactor

A lipase-immobilized biphasic membrane reactor was applied for the optical resolution of racemic 2-hydroxy octanoic acid. Lipase from Candida rugosa or Pseudomonas cepacia was used as a biocatalyst, and three kinds of capillary membranes were employed as immobilization supports. The (S)-isomer of racemic 2-hydroxy octanoic acid methyl and butyl esters was preferentially hydrolyzed by both lipases. Immobilized P. cepacia lipase showed higher enantio-selectivity in biphasic membrane reactor than the native one did in emulsion stirred tank reactor, while immobilized C. rugosa lipase showed smaller enantio-selectivity than the native one. The use of butyl ester instead of methyl ester led to higher enantio-selectivity in C. rugosa lipase immobilized membrane reactor. In the membrane reactors with P. cepacia lipase immobilized, reaction rate and enantio-selectivity were affected by the types of membranes employed and the amount of enzyme loaded on the membrane. By use of biphasic membrane reactor with P. cepacia lipase immobilized, (R)-isomer and (S)-isomer of 2-hydroxy octanoic acid were obtained at the optical purity of 0.95 and 0.99 respectively.

Catalytic Behaviour of Lipase Free and Immobilized in Biphasic Membrane Reactor with Different Low Water-Soluble Substrates

The catalytic activity and reaction rate of lipase have been studied using the biocatalyst free in an organic/aqueous emulsion and immobilized in a biphasic organic/aqueous membrane reactor. The first reaction system was realized in a stirred tank reactor. The other was obtained by immobilizing the enzyme in the sponge layer of an asymmetric capillary membrane and recirculating the two phases along the two separate circuits of the membrane module. The performance of the reactors has been studied using two different low water-soluble substrates: triglycerides present in commercial olive oil and (R,S)-cyanomethyl-[2-(4-isobutylphenyl)propionate] (CNE). The effects of substrate viscosity and flow dynamics conditions, such as organic phase flow rate, on the biphasic membrane reactor performance have been evaluated on the basis of observed reaction rate and catalytic activity of free and immobilized lipase for both substrates. It has been observed that free lipase showed higher catalytic activity with olive oil, while immobilized lipase showed higher catalytic activity with CNE which has a lower viscosity than olive oil. The increase of organic phase flow rate negatively affected the reactor performance, with a minor effect when using CNE rather than olive oil. The influence of temperature on the biocatalyst performance with the two substrates has also been investigated. The optimal temperature value of lipase was different for the two substrates: 28°C with CNE and 40°C with olive oil.