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Item type:Publication, Access status: with files , Multifunctional carbon‐nanotube supported catalyst for efficient glycerol hydrogenolysis to 1,2‐propanediol(Wiley, 2026-03); ; Multiwall carbon nanotube (NC7000) supported mono-, bi-, and trimetallic catalysts were synthesized and tested in a multi- batch reactor setup supported by data-driven modeling for the chemical hydrogenolysis of glycerol to 1,2-Propanediol (1,2-PDO) at 220◦C under 30 bar hydrogen pressure in aqueous solution. ICP-OES, N2 -physisorption, scanning electron microscopy (SEM), transmission electron microscopy (TEM), energy dispersive x-ray spectroscopy (EDX), powder x-ray diffraction (XRD) and x-ray photoelectron spectroscopy (XPS) were used to investigate the physico-chemical properties of the synthesized catalysts. Interesting structure-activity-selectivity correlations could be deduced from the different metal ratios and combinations. While Ru was by far the most active monometallic species ( X = 100%), followed by Pt ( X = 80%) and Ir ( X = 65%), it suffered from a very low 1,2-PDO selectivity ( S < 10%). Combining Ru with the more selective transition-metals RuX2 ( X = Fe, Co, or Ni) maintained the high activity ( X > 95%) but only moderately increased 1,2-PDO selectivity ( S = 20%–30%). Interestingly, combining Ru with Cu in a bimetallic RuCu2 catalyst slightly decreased activity ( X = 81%) but drastically improved 1,2-PDO selectivity ( S = 58%). Moreover, a trimetallic combination of RuMCu2 (M = Pt, Pd, Ir) did not further increase activity ( X = 50%–70%) but could push 1,2-PDO selectivity up to 79% for the trimetallic RuIrCu2 catalyst. Most prominently, a final metal ratio variation for the RuCux catalyst was derived with the help of the data-driven models producing the most promising RuCu3 /NC7000) catalyst combining both high activity ( X = 78%) with a very high 1,2-PDO selectivity ( S = 79%) resulting in the highest 1,2-PDO yield of 58% in a nearly closed carbon balance ( C > 95%). This lays the foundation for implementing this highly active and selective catalyst in a future SMART reactor for glycerol valorization.Publicationtype: Journal Article86 77 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Engineering catalysts at the multiscale: past, present, and future of catalyst manufacturing and shaping processes(Wiley-VCH, 2025-10-27); 59 23 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Rational design of hydrophilic deep eutectic solvents to outperform oxidoreductase activity in aqueous media(Wiley-VCH, 2025-10-08); ; ; Outperforming biocatalysis through nonconventional media opens new avenues in synthesis, from process intensification to industrial integration. While hydrophobic deep eutectic solvents (DESs) based on fatty acids have emerged as a promising landscape for oxidoreductases, the potential of hydrophilic DESs to rival or surpass aqueous systems remains largely underexplored. Building on findings that glycerol aids alcohol dehydrogenase (ADH) catalysis and choline chloride hinders it, this study designs enzyme-friendly glycerol-based DESs using betaine and sarcosine at varied ratios and water contents. Consistently, a higher glycerol fraction (mol:mol, 1:8) contributed to a stronger stabilizing effect on ADHs, and betaine emerged as the most favorable component, followed by sarcosine and choline chloride. Enzyme thermostability improved in Bet-Gly and Sar-Gly, though activity was lower in all hydrophilic DESs; Bet-Gly (1:8) with 80% buffer showed the best performance. Encouragingly, the enzyme's specific activity for the cyclohexanone reduction outperformed that observed in the pure buffer, and the optimal eutectic conditions of Bet-Gly (1:8) and Sar-Gly (1:8) with 60 vol.% buffer outperformed the pure buffer system in cinnamaldehyde reduction (a more industrially-sound reaction). This study advances DES research and aids in the design of DESs for redox biocatalysis in hydrophilic media.Publicationtype: Journal Article22 13 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Elemental analysis of catalysts in a fixed-bed reactor by laser-induced breakdown spectroscopyIn situ and operando characterization techniques provide molecular, surface, electronic, and structural information about catalysts in reactors. Accessing changes in the “Elemental Composition” of catalysts under reaction conditions remains yet an unsolved challenge. This work takes a first step in this direction by investigating the potential and limitations of Laser-Induced Breakdown Spectroscopy (LIBS) for monitoring catalyst deactivation, specifically during Dry Reforming of Methane over Ni/γ-Al2O3 and Propane Dehydrogenation over VOX/γ-Al2O3. The study increases complexity stepwise, starting from spatially resolved ex situ LIBS analysis of catalyst particles removed from the reactor after reaction, to the development of a fiber-optic LIBS system and time-resolved intra-reactor measurements. Spectroscopic measurements are complemented by monitoring catalyst activity and temperature at each stage. For the dry reforming of methane, a correlation was found between catalyst performance, temperature, and the spatial distribution of coke, with distinct zoning along the catalyst bed. A cost-effective fiber-optic LIBS probe was developed, allowing for intra-reactor measurements under harsh conditions. The LIBS probe was used to study catalyst deactivation and regeneration during propane dehydrogenation by measuring time-resolved carbon and vanadium profiles. A Partial Least Squares regression model was developed to correlate the amount of carbon deposits with the LIBS spectra, allowing the derivation of quantitative statements. Despite its limitations, such as invasiveness and gas sensitivity, the study highlights the potential of LIBS as an in situ/operando elemental analysis technique.Publicationtype: Journal Article60 28 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Linkers in Action: Exploring Fusion Enzymes for Oxyfunctionlizations in Non-Conventional Media Through Experiments and SimulationsBaeyer–Villiger monooxygenases (BVMOs) are key for the selective oxidation of ketones into diverse (cyclic) esters. However, challenges like oxygen and cofactor dependence and substrate/product inhibition hinder their broader application. To address some of these issues, nonconventional media have been applied; still, they lack certain water required for enzyme hydration and cofactor regeneration, reducing activity and/or stability. Fusion approaches enable efficient cofactor recycling by shortening the diffusion distance between enzyme active sites in cascades, especially under low-water conditions. Trial-and-error linker design and time-intensive construction of fusion enzymes substantially slow down the development of fusion enzymes. In this study, we present the work on the fusions of cyclohexanone monooxygenase (CHMO) and alcohol dehydrogenase (ADH) with linkers owing varying lengths and flexibility in both orientations in nonconventional media, focusing on understanding the effects of linkers on the structural and catalytic properties of fusion enzymes. As such, 12 new fusion enzymes were constructed and evaluated regarding the kinetics, specific activity, and stability, identifying the optimal ones for the linear oxyfunctionlization cascade in aqueous–organic biphasic systems. The conformation and flexibility of linkers and the spatial arrangement of fusion enzymes were studied with simulations, which provides a deep understanding of linkers’ influence and offers insights into the rational design of fusion enzymes.Publicationtype: Journal Article21 16 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Process Understanding of transamination reaction in chiral pharmaceutical intermediate production catalyzed by an engineered amine transaminase(Wiley, 2025-02-17); ; 26 17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Yeast surface display enables one-step production and immobilization of unspecific peroxygenasesUnspecific peroxygenases (UPOs) are regarded as a “dream catalyst” for selective oxyfunctionalization reactions like oxygenations. We present the display of the model UPO rAaeUPO (PaDa−I) on the cell surface of the heterologous production host Komagataella phaffii as a one-step production and immobilization process. The coding sequence for PaDa−I was combined with genes coding for cell wall proteins from Saccharomyces cerevisiae and transformed into K. phaffii. The fusion proteins were compared among each other and with secreted, free PaDa−I. One system in particular, a C-terminal fusion of PaDa−I and Sag1 yielded near identical activity per volume culture broth to the secreted PaDa−I with ~90 % of the activity being at the cell wall. The surface display simplifies downstream processing and includes immobilization on a cheap, retainable and replaceable matrix, that is the production host itself. The enzymes remained active in a repeated batch process for 10 batches and 200 h of catalysis.Publicationtype: Journal Article14 15 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Catalytic profile reactor for multimodal Operando measurements during periodic operation(Wiley-VCH, 2022-12-20); ; ; ; Multimodal operando measurement concepts aim to provide structure-activity relations of heterogeneously catalyzed reactions during operation. While the utilization of multiple characterization and spatiotemporally-resolved techniques provides complementary information at relevant time and length scales, different reactor operation modes allow to track catalyst dynamics. However, combining these measurement concepts require complex experimental setups with high demands from a strongly interdisciplinary field of reaction engineering, physics and chemistry. In this study, a fully automated and integrated catalytic profile reactor setup is introduced which is capable of measuring spatiotemporally-resolved species concentration, temperature and catalyst structure information under periodic reaction conditions. The oxidative dehydrogenation of C2H6 to C2H4 over MoO3/γ-Al2O3 was used as a test system. Using the periodic profile approach, the catalytic system was investigated through activity measurements resolved in time and space combined with reactor simulations and operando high-energy X-ray diffraction. The presented catalytic profile reactor setup is a versatile technology, aiming to promote combined and detailed analysis of local catalyst activity and structure, for improved reproducibility and quality of operando measurements.Publicationtype: Journal ArticleScopus© Citations 4 122 308 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enzymatic Oxidation of Butane to 2-Butanol in a Bubble Column(Wiley, 2020-06-09); ; ; ; Unspecific peroxygenases have recently gained significant interest due to their ability to catalyse the hydroxylation of non-activated C−H bonds using only hydrogen peroxide as a co-substrate. However, the development of preparative processes has so far mostly concentrated on benzylic hydroxylations using liquid substrates. Herein, we demonstrate the application of a peroxygenase for the hydroxylation of the inert, gaseous substrate butane to 2-butanol in a bubble column reactor. The influence of hydrogen peroxide feed rate and enzyme loading on product formation, overoxidation to butanone and catalytic efficiency is investigated at 200 mL scale. The process is scaled up to 2 L and coupled with continuous extraction. This setup allowed the production of 115 mmol 2-butanol and 70 mmol butanone with an overall total turnover number (TTN) of over 15.000, thereby demonstrating the applicability of peroxygenases for preparative hydroxylation of such inert, gaseous substrates at mild reaction conditions.Publicationtype: Journal ArticleScopus© Citations 11 494 302 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Enzyme immobilization on synthesized nanoporous silica particles and their application in a bi-enzymatic reaction(Wiley-VCH, 2020-01-27); ; ; ; The application of enzymes presents a great advantage regarding highly selective reactions; however, it involves also challenges due to their sensitivity. Immobilization offers one strategy to overcome those challenges enabling enzyme stabilization, as well as retention. In the present study, covalent attachment on hydrophilic amino-functionalized carriers is found to be the most promising immobilization method for the investigated reaction system. To achieve this, a novel method for preparation of silica particles with subsequent amino-functionalization is developed to prepare spherical carriers for enzyme immobilization, whereby high porosities are obtained based on polymerization. With these particles, immobilization of an alcohol dehydrogenase and a formate dehydrogenase is realized with residual activities of 70 and 80 % after 12 consecutive batches, respectively. The two immobilized enzymes are used in the reduction of cinnamyl aldehyde with in situ cofactor regeneration, obtaining a conversion of 100 % and up to 10-fold higher turnover numbers compared to the free enzyme.Publicationtype: Journal ArticleScopus© Citations 21 245 327