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Item type:Publication, Access status: with files , Kinetic modeling and optimization of complex enzymatic reactions: a practical guide for chemists and biotechnologists(Royal Society of Chemistry (RSC), 2026-09-03); ; ; 118 1 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enzyme immobilization on stimuli-responsive hydrogels - Part B. Impact of carrier responsiveness on reactor performance(American Chemical Society (ACS), 2026-06-25); ; ; ; Stimuli-responsive gels, known as smart materials, undergo reversible changes through solvent uptake or expulsion. Building on prior material characterization (Paper A), this study evaluates their performance in a plug-flow reactor under changing temperature (25–40 °C) and pH (8–4) conditions using formate dehydrogenase for NADH regeneration from NAD+. Temperature changes caused transient increases in activity at elevated temperatures, followed by partial or pronounced loss after returning to mild conditions, indicating limited effects of gel responsiveness. In contrast, under pH changes, activity decreased under acidic conditions but fully recovered for responsive hydrogels, maintaining high residual activity (93.3 ± 26.3% for pH-responsive and 91.0 ± 9.8% for dual-responsive carriers), whereas non-responsive silica carriers showed irreversible loss, retaining only 27.6 ± 10.2% of the initial yield. This behavior is attributed to gel shrinkage, which restricts mass transport and reduces enzyme exposure to the surrounding environment. These results demonstrate the potential of responsive hydrogels as adaptive enzyme carriers for biocatalysis.Publicationtype: Journal Article69 65 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enzyme immobilization on stimuli-responsive hydrogels - Part A. Influence of carrier properties on immobilization efficiency and catalytic performance(American Chemical Society (ACS), 2026-06-25); ; ; ; Enzyme immobilization on stimuli-responsive hydrogels provides a strategy to control biocatalytic activity under fluctuating process conditions. In this study, the immobilization of formate dehydrogenase on three hydrogel carriers is investigated: pH-responsive poly(2-hydroxyethyl methacrylate-co-itaconic acid), temperature-responsive poly(N-isopropylacrylamide), and dual-responsive poly(N-isopropylacrylamide-co-itaconic acid). The hydrogels were characterized in terms of swelling behavior, mechanical properties, and morphology, confirming the responsiveness of these materials. Subsequently, the immobilization performance was evaluated across two carrier geometries (monoliths and particles) and two immobilization techniques (adsorption and covalent binding). The polymer chemistry was identified as the dominant factor controlling enzyme loading density, with the dual-responsive formulation achieving the highest loading despite moderate immobilization yields. These responsive hydrogels demonstrate strong potential as smart enzyme carriers for biocatalytic applications, particularly in continuous-flow reactor designs where improved substrate availability and increased convection can mitigate diffusion limitations and fully exploit both the catalytic performance and stimuli-responsive properties of the immobilized enzyme systems.Publicationtype: Journal Article84 75 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , CO₂-driven pH control in the enzymatic hydrolysis of urea: a coupled modeling-experiment approach(American Chemical Society (ACS), 2026-06-25); ; ; ; Enzymatic biotransformations can offer sustainable alternatives to conventional chemical processes, but their activity often strongly depends on the pH of the reaction solution. The urease-catalyzed hydrolysis of urea provides a mild route for ammonia production; however, this ammonia production inherently increases the pH in a buffer-free system, rapidly decreasing urease activity. In this work, we combine modeling and experiments to develop a buffer-free pH control strategy for the enzymatic hydrolysis of urea that relies on the dissolution of gaseous carbon dioxide (CO₂). CO₂, which is actually a byproduct of enzymatic urea hydrolysis, is deliberately added to regulate the pH and enhance productivity. A kinetic model for urea hydrolysis is coupled with a thermodynamic model of the acid–base equilibria in the aqueous phase to analyze and design the process. Bayesian optimization is applied to calculate the optimal partial pressures for CO₂ in the gas phase to maximize productivity. The resulting concept is successfully demonstrated experimentally, highlighting a practical approach with minimal downstreaming requirements to control pH in enzymatic reactions.Publicationtype: Journal Article77 112 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , A novel approach for visualizing mixing phenomena of reactive liquid-liquid flows in milli- and micro-channels(Frontiers Media S.A., 2022-06-06); ; ; ; Modular milli- and micro-structured systems represent a promising approach to exploit the potential of micro-process technology, including precise reaction control and scale-up. A major drawback of micro-structured devices is fouling and mixing mechanisms need to be investigated phenomenologically to better understand the processes that lead to fouling. Previous work was conducted to resolve 3D concentration fields by means of Laser-Induced Fluorescence (LIF) using a Confocal Laser Scanning Microscope (CLSM) (Frey et al., J Flow Chem, 2021, 11, 599–609). While the CLSM-LIF method yields detailed insight into concentration fields down to a few micrometers, it is limited to stationary flow structures only. Aubin et al. (Chemical Engineering Science, 2010, 65, 2065–2093) give a comprehensive review of methods to analyze mixing behavior. Most recent optical measurement methods rely on the detection of a single compound in mixtures. In case of reactive mixing, Tthe state of the art procedures to locally visualize micro mixing relies on tracking a reaction product which forms on molecular scale. In literature, only small micro-structures are manufactured from transparent materials, however larger milli-structures often lack optical accesses with sufficient quality. Selective laser-induced etching (SLE) is a new technique which enables the fabrication of larger milli-structures in transparent materials that are relevant for industry-scale applications. This work develops a method based on a concept of Kexel et al. (Chemie Ingenieur Technik, 2021, 93, 830–837) visualizing the selectivity of a competitive-consecutive gas-liquid reaction in a Taylor bubble flow. The main goal of this work is the analysis of the absorbance spectra of bromothymol blue (BTB) at different pH values in a miscible liquid-liquid system in a fused silica split-and-recombine mixer. The milli-structure of the mixer is manufactured by means of SLE. Backlight at different wavelengths is pulsed matching the recording frequency. In contrast to conventional UV/Vis setups, the absorbance is recorded locally within the mixer. The proposed method yields the 2D concentration distribution of multiple species with high spatial resolution. The spatially resolved reactant and product distribution unveils micro mixing and can yield important information about local root causes of fouling.Publicationtype: Journal ArticleScopus© Citations 1 151 532