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Item type:Publication, Access status: with files , Electrostatic engineering of Phosphoketolase enhances activity on small nonphosphorylated sugars and improves cell-free ATP regeneration from inexpensive C2‑substrates(American Chemical Society, 2026-07-28); ; ; Phosphoketolases can convert nonphosphorylated sugars to the high-energy compound acetyl phosphate and the versatile metabolic precursor acetyl-CoA. However, their application is limited by low catalytic activity toward these substrates. Here, we report the rational engineering of the phosphoketolase from Bifidobacterium adolescentis (Bad.F6Pkt) to enhance its activity and affinity toward glycolaldehyde (GA) and d-erythrulose (ERU) through reorganization of the protein electric field. Guided by predicted induced side-chain pKa shifts, visualization of electrostatic potential difference maps alongside molecular modeling and sequence variation analyses, we identified mutations that could promote in situ ring opening of the predominant cyclic GA dimer. This approach yielded the GA-specific double mutant H142N:E153D, exhibiting a 10-fold improved affinity (KM = 4.4 mM) and slightly enhanced catalytic efficiency compared to the previously reported H142N variant. In addition, the H256Y:H260Y:H548Y variant comprising long-range electrostatic mutations exhibited a 3.8-fold higher catalytic efficiency toward ERU than the wild-type. The engineered enzymes were evaluated in cell-free enzyme cascades for ATP regeneration via acetyl phosphate formation. The H142N variant enabled efficient ATP regeneration from GA and ethylene glycol, whereas H142N:E153D exhibited reduced stability under synthesis conditions. Furthermore, coupling of a d-threose aldolase and isomerase with the PKT triple mutant enabled rapid GA conversion to C4 sugar intermediates, increasing the ATP yield.Publicationtype: Journal Article24 4 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Development of an experimental setup and a validated model for a highly integrated biocatalytic process(American Chemical Society (ACS), 2026-07-23); ; ; ; The development and validation of a mathematical model for a highly integrated biocatalytic process are presented. A multienzymatic cascade comprising three parallel and sequential reaction steps was implemented in a miniplant setup, integrating an enzyme membrane reactor (EMR) and a reactive extraction centrifuge (REC) to enable intensified biotransformations. Laboratory-scale experiments were conducted to obtain the kinetic and thermodynamic data necessary for model development. The resulting process model captures both the enzymatic reaction kinetics and the dynamic behavior of the integrated unit operations. Model validation was performed under representative process conditions in the miniplant system. The results demonstrate good agreement between the model and experimental data, confirming the predictive power of the model and supporting its use in future process design, scale-up, and optimization. This work underscores the importance of model-based development for advancing sustainable and efficient biocatalytic processes.Publicationtype: Journal Article27 9 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Advancements in cofactor regeneration for efficient UDP-GlcNAc and UDP-GalNAc synthesis(Elsevier, 2026-06-26); ; ; UDP-GlcNAc and UDP-GalNAc are well-demanded nucleotide sugars and serve as precursors for the enzymatic synthesis of N- and O-glycans as well as glycosaminoglycans. Although the enzymatic synthesis cascade has been extensively studied, limitations remain for an efficient large-scale production. Unfavorable inhibitions by intermediate accumulation, precipitation of the byproduct phosphate with the needed cofactor magnesium, and efficient enzyme dosage still pose significant challenges. These challenges were investigated in an enzyme cascade including N -acetyl-hexosamine kinase from Bifidobacterium longum ( Bl NahK), UDP- N -acetylgalactosamine diphosphorylase from Homo sapiens ( Hs AGX1), and inorganic pyrophosphatase from Pasteurella multocida ( Pm PpA) for UDP-GlcNAc and UDP-GalNAc synthesis. ATP supply started from AMP and polyphosphate by polyphosphate kinase from Cytophaga hutchinsonii ( Ch PPK), and UTP was generated from UMP using cytidine/uridine monophosphate kinase from Escherichia coli ( Ec CMPK) and cytidine/uridine diphosphate kinase from Saccharomyces cerevisiae ( Sc CDPK). To reach a high productivity, enzyme cascade parameters were determined and optimized using Multiplex capillary electrophoresis. By kinetic modelling of the enzyme cascade and fine-tuning of the uncoupled UTP/ATP generation/regeneration system as well as observing the magnesium polyphosphate interplay with enzyme activity we were able to scale the production up to a molarity of 100 mM in 200 mL, yielding 10 g of UDP-GlcNAc with a conversion of 82.4% in 48 h and 12 g of UDP-GalNAc with full conversion in 29 h. The key limitations for successful scale-up, namely the promiscuity of Bl NahK towards UTP and interplay of magnesium ions with phosphate species, were overcome. Overall, the presented insights are expected to be transferable to similar enzyme cascades.Publicationtype: Journal Article48 11 - 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 Article77 68 - 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 Article68 63 - 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 Article76 98 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Autonomous flow control by a responsive poly(2-hydroxyethyl acrylate) organogel-valve during the aerobic oxidation of benzyl alcohol(American Chemical Society (ACS), 2026-06-05); ; ; Macroscopic poly(2-hydroxyethyl acrylate) organogel beads were synthesized and applied as a chemoresponsive component in a smart valve. Monodisperse round beads of about 3 mm diameter were obtained by cryogenic dripping and subsequent UV photopolymerization of the frozen aqueous monomer solution. The synthesis yields dimensionally stable, soft spheres with a macroporous architecture. The elastic modulus increases from the soft, swollen state in benzyl alcohol to over 250 kPa for high-density networks in the collapsed state in benzaldehyde. They have a degree of swelling in benzaldehyde lower by a factor of 3–7 to that in benzyl alcohol, in dependence of the amount of polyethylene glycol diacrylate cross-linker in the precursor solution. Upon exposure to benzaldehyde, the beads become opaque, indicating a phase transition. Kinetic analysis of the bead volume change for swelling in benzyl alcohol and shrinkage in benzaldehyde gives half-life times in the range of 2–5 min. Beads exhibiting a macroscopic volume change of up to 71% were confined in a casing and acted as a smart valve in a reactor system. The aerobic oxidation of benzyl alcohol to benzaldehyde with a TEMPOL/copper acetate catalyst mixture demonstrated the high efficiency and practical applicability of the self-regulating flow-control component.Publicationtype: Journal Article29 48 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Investigation of combined alkaline pretreatment and mechanoenzymatic processing for improved valorization of post-consumer textiles(Wiley-VCH, 2026-06-04); ; ; ; The continuous increase in textile waste, coupled with insufficient recycling and reuse strategies, has led to a growing issue of underutilized raw materials. Mixed textiles account for approximately 50% of global textile waste and commonly consist of tightly woven cotton blended with synthetic fibers, which complicated material separation and recovery. This study presents an integrated approach that combines mechanochemical pretreatment with subsequent mechanoenzymatic processing to valorize such complex waste streams. Using sodium hydroxide during milling enables higher solids loadings and supports efficient processing under moderate conditions. The mechanochemical approach yields glucose recoveries of up to 80.57% after 24 h. Furthermore, coupling mechanochemical and mechanoenzymatic treatment increases glucose yield by approximately 30% within 6 h, compared with conventional treatment strategies. This combined approach offers a scalable and sustainable pathway for converting mixed textile waste into valuable products. The process facilitates the selective recovery of polyethylene terephthalate (PET) while preserving its essential properties, enabling its reuse in subsequent applications or incorporation into established recycling pathways. Beyond the recovery of cellulose as glucose, this technology may enable the selective extraction of PET fibers, providing the basis for more efficient biotechnological processes and promoting enhanced circularity in PET fiber recycling.Publicationtype: Journal Article20 19 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Esterification in an autonomously controlled reactor: exploiting the chemo-mechanical properties of a smart organogel(American Chemical Society (ACS), 2026-06-04); ; ; ; Iron(III)-reinforced poly(N-isopropylacrylamide-co-acrylic acid) organogel beads inside a casing give an intrinsic chemo-mechanical valve. The valve was incorporated in a setup with a stirred reactor for the heterogeneously acid-catalyzed esterification of acetic acid and ethanol. A noninvasive gravimetric control loop was used to validate the autonomous modulation of the hydrodynamic residence time in response to the composition of the reaction mixture. Operating at a 1:1 molar feed ratio, the valve restricted the initial outflow to less than 7 mL·min–1 and autonomously ramped up to a steady state flow of 135 mL·min–1 as the esterification approached thermodynamic equilibrium. The valve opening rate was about half of the reaction rate. The ionically reinforced organogel had enough resilience inside the casing for multiple uses. Soft actuators were thus successfully applied for reaching a self-regulating reactor loop driven by intrinsic chemical feedback of a smart material.Publicationtype: Journal Article76 65 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Experimental studies on microscopic, multiphase transport phenomena: novel applications of light sheet fluorescence microscopy(Springer Science and Business Media Deutschland GmbH, 2026-05-26); ; ; ; Over the past two decades, light sheet fluorescence microscopy has developed to a powerful tool for studies of dynamics in biological systems. In a new development, we apply light sheet fluorescence microscopy as a novel experimental measurement technology within the field of multiphase process engineering and fluid dynamics. The technology enables a number of novel studies of single- and multiphase transport phenomena on a microscopic scale. In the current publication, we introduce the first implementation of light sheet fluorescence microscopy in the field and demonstrate its applicability on one exemplary measurement of diffusive oxygen mass transfer from an oxygen bubble to degassed water. The results prove that such measurements can be conducted with a high spatial resolution with a submicron pixel pitch and enable precise studies on microscopic transport phenomena. Besides measurements of mass transfer, on which we lay the focus here, light sheet fluorescence microscopy further enables studies of fluid dynamics on a microscopic scale.Publicationtype: Journal Article73 16