Enzyme hydrolysis of soybean oil in a slug flow microsystem

Enzymatic Degradation of 2,4,6-Trichlorophenol in a Microreactor using Soybean Peroxidase

Soybean peroxidase is an enzyme extracted from soybean seed hulls. In the presence of hydrogen peroxide, the enzyme has the potential to catalyze the biodegradation of toxic substances like chlorophenols. For this reason, its use in wastewater treatment processes is environmentally friendly since the enzyme can be obtained from a renewable and abundant raw material. In this work, enzymatic biodegradation of 2,4,6-trichlorophenol performed by soybean peroxidase in a microreactor was studied experimentally and theoretically. The experimental data set was obtained with a volume of 250 μL by using different soybean peroxidase concentrations and different reaction times. The fluid dynamics of the microreactor was modeled as well, using ANSYS CFX. The simulations exhibited secondary flows, which enhanced mixing. Although the laminar flow was developed, it can be assumed to be a well-mixed medium. The kinetic data were evaluated through a mechanistic model, the modified bi-bi ping-pong model, which is adequate to represent the enzymatic degradation using peroxidases. The model was composed of an initial value problem for ordinary differential equations that were solved using MATLAB. Some kinetic constants were estimated using the least square function. The results of the model fit well the experimental data.

Theoretical study on enzyme synthesis of cephalexin in a parallel-flow microreactor combined with electrically driven ATPS microextraction

A mathematical model of a microfluidic device with two aqueous phases for the simultaneous cephalexin production and its separation from a reaction mixture was developed. The model anticipates the continuous cephalexin synthesis and enzyme recyclation.

Synthesis of alginate-silica hybrid hydrogel for biocatalytic conversion by β-glucosidase in microreactor

The organic-inorganic hybrid materials have been used in different fields to immobilize biomolecules since they offer many advantages. The aim of this study was to optimize and characterize the alginate-silica hybrid hydrogel as a stable and injectable form for microfluidic systems using internal gelation method and increase the stability and activity of immobilized enzyme for biocatalytic conversions as well. Characterization was carried out by scanning electron microscopy, energy dispersive spectroscopy/mapping, Brunauer-Emmett-Teller, Barrett-Joyner-Halenda, and Fourier-transform infrared spectroscopy analyses, and the shrinkages of monoliths were evaluated. Subsequent to optimizing the enzyme concentration (40 μg), hydrolytic conversion of 4-nitrophenyl β-d-glucopyranoside (pNPG) was performed to understand the behavior of the bioconversion in the microfluidic system. The yield was 94% which reached the equilibrium at 24 h indicating that the alginate-silica gel derived microsystem overcome some drawbacks of monolithic systems. Additionally, bioconversion of Ruscus aculeatus saponins was carried out at the same setup in order to obtain aglycon part, which has pharmaceutical significance. Although pure aglycon could not be achieved, an intermediate compound was obtained based on the HPLC analysis. The developed formulation can be utilized for various life science applications.

Optimization of aqueous two-phase systems for the production of 6-aminopenicillanic acid in integrated microfluidic reactors-separators

Aqueous two-phase systems (ATPSs) were screened for the production of 6-aminopenicillanic acid (6-APA) catalyzed by penicillin acylase, followed by the extractive separation of 6-APA from the reaction mixture. The key point of this study was to find an ATPS exhibiting a large difference in the partition coefficients of the biocatalyst and reaction products. Several ATPSs based on polyethylene glycol (PEG)/phosphate, PEG/citrate, and PEG/dextran were tested. We found that an ATPS consisting of 15 wt% of PEG 4000, 10 wt% of phosphates, 75 wt% of water (pH value 8.0 after dissolution) provided optimal separation of 6-APA from the enzyme. While the 6-APA was mainly found in the top PEG phase, the free enzyme favored the bottom salt-rich phase. This ATPS also fulfils other important requirements: (i) high buffering capacity, reducing an undesirable pH decrease due to the dissociation of phenylacetic acid (the side product of the reaction), (ii) a relatively low cost of the ATPS components, (iii) the possibility of electrophoretic transport of fine droplets as well as the reaction products for both the acceleration of phase separation and the enhancement of 6-APA concentration in the product stream. Extraction experiments in microcapillary and batch systems showed that the transport of 6-APA formed in the salt-rich phase to the corresponding PEG phase could occur within 30 s. The experimental results described form a base of knowledge for the development of continuously operating integrated microfluidic reactors-separators driven by an electric field for the efficient production of 6-APA.

A. Enzymatic microreactors in biocatalysis: history, features, and future perspectives

Microfluidic reaction devices are a very promising technology for chemical and biochemical processes. In microreactors, the micro dimensions, coupled with a high surface area/volume ratio, permit rapid heat exchange and mass transfer, resulting in higher reaction yields and reaction rates than in conventional reactors. Moreover, the lower energy consumption and easier separation of products permit these systems to have a lower environmental impact compared to macroscale, conventional reactors. Due to these benefits, the use of microreactors is increasing in the biocatalysis field, both by using enzymes in solution and their immobilized counterparts. Following an introduction to the most common applications of microreactors in chemical processes, a broad overview will be given of the latest applications in biocatalytic processes performed in microreactors with free or immobilized enzymes. In particular, attention is given to the nature of the materials used as a support for the enzymes and the strategies employed for their immobilization. Mathematical and engineering aspects concerning fluid dynamics in microreactors were also taken into account as fundamental factors for the optimization of these systems.

Characterization and modeling of multiphase flow in structured microreactors: a post microreactor case study

We study microreactors with internal fields of posts as typical examples of structured microreactors to elucidate flow fields and their implications for mass transfer. Laser-induced fluorescence (LIF) visualization combined with image analysis is used to systematically quantify key features such as interfacial area, phase holdup and the characteristics of the post-wetting layer. The subsequent mass transport analysis yields insight into how the posts contribute to the overall enhanced mass transfer performance compared to open channels, and provides predictions of mass transfer performance under varying operating conditions. Computational fluid dynamic (CFD) simulations of multiphase flow using the volume-of-fluid (VOF) method are in good agreement with experimentally observed multiphase flows.

Impact of mass transport on the enzymatic hydrolysis of rapeseed oil

In order to assess the capillary segmented flow reactor as a potentially appropriate reactor device for the enzymatic hydrolysis of vegetable oils, a study was made to reveal the impact of incident mass transfer processes on the hydrolysis rate. As demonstrated by means of experiments performed in a modified Lewis-cell type contactor, which allows the independent adjustment of flow rates for both phases, the enzymatic hydrolysis rate of rapeseed oil is strongly governed by mass transport processes taking place in both phases. In the oil phase, any increase in convective mass transfer results in an enhancement of hydrolysis rate due to facilitated removal of fatty acids from interface layer which is known to inhibit the activity of the enzyme adsorbed at the interface. At asynchronous condition when solely the water phase is agitated, however, convective mass transport in the interface layer has an inverse effect on the hydrolysis rate due to the generation of considerable shear stress in the vicinity of the interface unfavorable for the performance of the enzymes. By operating at synchronous agitation conditions, the shear stress can considerably be reduced. Generally, the positive effect of mass transport in the oil phase compensates the negative one in the aqueous phase thus resulting in an overall increase in hydrolysis rate of 57% with increasing stirrer rates. The results can be applied to the operation of segmented-flow capillary reactors by choosing the oil phase as disperse phase and the water phase as continuous phase, respectively.

Combi-lipase for heterogeneous substrates: a new approach for hydrolysis of soybean oil using mixtures of biocatalysts

The concept of thecombi-lipasebiocatalyst has been proposed. It is based on the combination of different lipases as biocatalysts in reactions using heterogeneous substrates.

Three-phase slug flow in microchips can provide beneficial reaction conditions for enzyme liquid-liquid reactions

Here, we introduce a solution to low stability of a two-phase slug flow with a chemical reaction occurring at the phase interface in a microfluidic reactor where substantial merging of individual reacting slugs results in the loss of uniformity of the flow. We create a three-phase slug flow by introducing a third fluid phase into the originally two-phase liquid-liquid slug flow, which generates small two-phase liquid slugs separated by gas phase. Introduction of the third phase into our system efficiently prevents merging of slugs and provides beneficial reaction conditions, such as uniform flow pattern along the whole reaction capillary, interfacial area with good reproducibility, and intensive water-oil interface renewal. We tested the three-phase flow on an enzyme hydrolysis of soybean oil and compared the reaction conversion with those from unstable two-phase slug flows. We experimentally confirmed that the three-phase slug flow arrangement provides conversions and pressure drops comparable or even better with two-phase liquid-liquid arrangements.