An enzymatic continuous-flow reactor based on a pore-size matching nano- and isoporous block copolymer membrane

Continuous-flow biocatalysis utilizing immobilized enzymes emerged as a sustainable route for chemical synthesis. However, inadequate biocatalytic efficiency from current flow reactors, caused by non-productive enzyme immobilization or enzyme-carrier mismatches in size, hampers its widespread application. Here, we demonstrate a general-applicable and robust approach for the fabrication of a high-performance enzymatic continuous-flow reactor via integrating well-designed scalable isoporous block copolymer (BCP) membranes as carriers with an oriented and productive immobilization employing material binding peptides (MBP). Densely packed uniform enzyme-matched nanochannels of well-designed BCP membranes endow the desired nanoconfined environments towards a productive immobilized phytase. Tuning nanochannel properties can further regulate the complex reaction process and fortify the catalytic performance. The synergistic design of enzyme-matched carriers and efficient enzyme immobilization empowers an excellent catalytic performance with >1 month operational stability, superior productivity, and a high space-time yield (1.05 × 105 g L-1 d-1) via a single-pass continuous-flow process. The obtained performance makes the designed nano- and isoporous block copolymer membrane reactor highly attractive for industrial applications.

Developing Enzyme Immobilization with Fibrous Membranes: Longevity and Characterization Considerations

Fibrous membranes offer broad opportunities to deploy immobilized enzymes in new reactor and application designs, including multiphase continuous flow-through reactions. Enzyme immobilization is a technology strategy that simplifies the separation of otherwise soluble catalytic proteins from liquid reaction media and imparts stabilization and performance enhancement. Flexible immobilization matrices made from fibers have versatile physical attributes, such as high surface area, light weight, and controllable porosity, which give them membrane-like characteristics, while simultaneously providing good mechanical properties for creating functional filters, sensors, scaffolds, and other interface-active biocatalytic materials. This review examines immobilization strategies for enzymes on fibrous membrane-like polymeric supports involving all three fundamental mechanisms of post-immobilization, incorporation, and coating. Post-immobilization offers an infinite selection of matrix materials, but may encounter loading and durability issues, while incorporation offers longevity but has more limited material options and may present mass transfer obstacles. Coating techniques on fibrous materials at different geometric scales are a growing trend in making membranes that integrate biocatalytic functionality with versatile physical supports. Biocatalytic performance parameters and characterization techniques for immobilized enzymes are described, including several emerging techniques of special relevance for fibrous immobilized enzymes. Diverse application examples from the literature, focusing on fibrous matrices, are summarized, and biocatalyst longevity is emphasized as a critical performance parameter that needs increased attention to advance concepts from lab scale to broader utilization. This consolidation of fabrication, performance measurement, and characterization techniques, with guiding examples highlighted, is intended to inspire future innovations in enzyme immobilization with fibrous membranes and expand their uses in novel reactors and processes.

Macroporous Polymer Monoliths for Affinity Chromatography and Solid-Phase Enzyme Processing

Nowadays, monolithic stationary phases, because of their special morphology and enormous permeability, are widely used for the development and realization of fast dynamic and static processes based on the mass transition between liquid and solid phases. These are liquid chromatography, solid-phase synthesis, microarrays, flow-through enzyme reactors, etc. High-performance liquid chromatography on monoliths, including the bioaffinity mode, represents unique technique appropriate for fast and efficient separation of biological (macro)molecules of different sizes and shapes (proteins, nucleic acids, peptides), as well as such supramolecular systems as viruses.In the edited chapter, the examples of the application of commercially available macroporous monoliths for modern affinity processing are presented. In particular, the original methods developed for efficient isolation and fractionation of monospecific antibodies from rabbit blood sera, the possibility of simultaneous affinity separation of protein G and serum albumin from human serum, the isolation of recombinant products, such as protein G and tissue plasminogen activator, respectively, are described in detail. The suggested and realized multifunctional fractionation of polyclonal pools of antibodies by the combination of several short monolithic columns (disks) with different affinity functionalities stacked in the same cartridge represents the original and practically valuable method that can be used in biotechnology. In addition, macroporous monoliths were adapted to the immobilization of such different enzymes as polynucleotide phosphorylase, ribonuclease A, α-chymotrypsin, chitinolytic biocatalysts, β-xylosidase, and β-xylanase. The possibility of use of immobilized enzyme reactors based on monoliths for different purposes is demonstrated.

Design of the Enzyme-Carrier Interface to Overcome the O2 and NADH Mass Transfer Limitations of an Immobilized Flavin Oxidase

Understanding how the immobilization of enzymes on solid carriers affects their performance is paramount for the design of highly efficient heterogeneous biocatalysts. An efficient supply of substrates onto the solid phase is one of the main challenges to maximize the activity of the immobilized enzymes. Herein, we apply advanced single-particle analysis to decipher the optimal design of an immobilized NADH oxidase (NOX) whose activity depends both on O₂ and NADH concentrations. Carrier physicochemical properties and its functionality along with the enzyme distribution across the carrier were implemented as design variables to study the effects of the intraparticle concentration of substrates (O₂ and NADH) on the activity. Intraparticle O₂-sensing analysis revealed the superior performance of the enzyme immobilized at the outer surface in terms of effective supply of O₂. Furthermore, the co-immobilization of NADH and NOX within the tuned surface of porous microbeads increases the effective concentration of NADH in the surroundings of the enzyme. As a result, the optimal spatial organization of NOX and its confinement with NADH allow a 100% recovery of the activity of the soluble enzyme upon the immobilization process. By engineering these variables, we increase the NADH oxidation activity of the heterogeneous biocatalyst by up to 650% compared to NOX immobilized under suboptimal conditions. In conclusion, this work highlights the rational design and engineering of the enzyme-carrier interface to maximize the efficiency of heterogeneous biocatalysts.

Towards the Development of a 3-D Biochip for the Detection of Hepatitis C Virus

The early diagnostics of hepatitis C virus (HCV) infections is currently one of the most highly demanded medical tasks. This study is devoted to the development of biochips (microarrays) that can be applied for the detection of HCV. The analytical platforms of suggested devices were based on macroporous poly(glycidyl methacrylate-co-di(ethylene glycol) dimethacrylate) monolithic material. The biochips were obtained by the covalent immobilization of specific probes spotted onto the surface of macroporous monolithic platforms. Using the developed biochips, different variants of bioassay were investigated. This study was carried out using hepatitis C virus-mimetic particles (VMPs) representing polymer nanoparticles with a size close to HCV and bearing surface virus antigen (E2 protein). At the first step, the main parameters of bioassay were optimized. Additionally, the dissociation constants were calculated for the pairs “ligand–receptor” and “antigen–antibody” formed at the surface of biochips. As a result of this study, the analysis of VMPs in model buffer solution and human blood plasma was carried out in a format of direct and “sandwich” approaches. It was found that bioassay efficacy appeared to be similar for both the model medium and real biological fluid. Finally, limit of detection (LOD), limit of quantification (LOQ), spot-to-spot and biochip-to-biochip reproducibility for the developed systems were evaluated.

Biodegradation of bisphenol A by the immobilized laccase on some synthesized and modified forms of zeolite Y

Bisphenol A (BPA) is an environmental pollutant with adverse effects on different ecosystems. In this study, immobilized laccase enzymes onto inorganic supports were used to remove BPA. Laccase was successfully immobilized on sodium zeolite Y (NaY) and its modified desilicated (DSY) and dealuminated (DAY) forms. NaY-based supports were instrumentally characterized. The immobilized laccase on NaY (laccase@NaY), desilicated (laccase@DSY), and dealuminated (laccase@DAY) forms showed significant improvement on immobilization yield (IY%) and efficiency (IE%). Laccase@DSY and laccase@NaY showed IY% = 73.18 ± 3.33 % and 46.23 ± 1.81 % and IE% = 94.50 ± 1.86 %, and 74.39 ± 1.41 %, respectively, whereas IY% and IE% for laccase@DAY were achieved as 81.12 ± 1.32 % and 98.56 ± 2.93 %, respectively. The supports also increased the enzyme characteristics such as pH-temperature range, catalytic stability, and reusability. K_m values were 0.73 ± 0.05, 0.26 ± 0.09, 0.31 ± 0.5, and 1.01 ± 0.03 mM for laccase@NaY, laccase@DAY, laccase@DSY, and the free enzyme, respectively. The enzyme demonstrated higher biodegradation ability of bisphenol A upon immobilization on the supports compared to that of the soluble enzyme. A bio-removal yield of 86.7 % was obtained considering three parameters including amount of laccase@DAY (8 U mg^-1), concentration of BPA (0.5 mM), and treatment time (1 h) based on response surface methodology (RSM). Biodegradation metabolites (49 ± 5.8 %) and unconverted BPA (14 ± 5.2 %) were analyzed by gas chromatography-mass spectrometry.

Investigating Monoliths (Vinyl Azlactone-co-Ethylene Dimethacrylate) as a Support for Enzymes and Drugs, for Proteomics and Drug-Target Studies

Prior to mass spectrometry, on-line sample preparation can be beneficial to reduce manual steps, increase speed, and enable analysis of limited sample amounts. For example, bottom-up proteomics sample preparation and analysis can be accelerated by digesting proteins to peptides in an on-line enzyme reactor. We here focus on low-backpressure 100 μm inner diameter (ID) × 160 mm, 180 μm ID × 110 mm or 250 μm ID × 140 mm vinyl azlactone-co-ethylene dimethacrylate [poly(VDM-co-EDMA)] monoliths as supports for immobilizing of additional molecules (i.e., proteases or drugs), as the monolith was expected to have few unspecific interactions. For on-line protein digestion, monolith supports immobilized with trypsin enzyme were found to be suited, featuring the expected characteristics of the material, i.e., low backpressure and low carry-over. Serving as a functionalized sample loop, the monolith units were very simple to connect on-line with liquid chromatography. However, for on-line target deconvolution, the monolithic support immobilized with a Wnt pathway inhibitor was associated with numerous secondary interactions when exploring the possibility of selectively trapping target proteins by drug-target interactions. Our initial observations suggest that (poly(VDM-co-EDMA)) monoliths are promising for e.g., on-line bottom-up proteomics, but not a "fit-for-all" material. We also discuss issues related to the repeatability of monolith-preparations.

Click chemistry at the microscale

This manuscript reviews recent developments in click chemistry in microscale systems.

Smart blood spots for whole blood protein analysis

A reactor for whole blood sampling integrated with instant protein digestion in a “lab-on-paper” format is introduced here.

Flow Bioreactors as Complementary Tools for Biocatalytic Process Intensification

Biocatalysis has widened its scope and relevance since new molecular tools, including improved expression systems for proteins, protein and metabolic engineering, and rational techniques for immobilization, have become available. However, applications are still sometimes hampered by low productivity and difficulties in scaling up. A practical and reasonable step to improve the performances of biocatalysts (including both enzymes and whole-cell systems) is to use them in flow reactors. This review describes the state of the art on the design and use of biocatalysis in flow reactors. The encouraging successes of this enabling technology are critically discussed, highlighting new opportunities, problems to be solved and technological advances.