Universität Stuttgart
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Item Open Access Integrated process design and optimisation for the production of cellobiose lipids from Ustilago sp.(2024) Oraby, Amira; Rupp, Steffen (Prof. Dr.)Item Open Access Tunable, permanent and instantly available super-wettability states on metal surfaces by laser texturing and plasma coating(2025) Holder, Daniel; Reichle, Paul; Umlauf, Georg; Weber, Rudolf; Barz, Jakob; Graf, ThomasWettability, the ability of a liquid to spread on or repel from a surface, holds particular significance for applications requiring extreme control of liquid interaction, including self-cleaning, anti-icing, dropwise condensation, anti-fogging, and enhanced fluid transport. This work investigates the synergistic combination of laser surface texturing and plasma-enhanced chemical vapor deposition (PECVD) to achieve tunable, permanent, and instantly available super-wettability states on metal surfaces. Ultrashort laser pulses were employed to produce various surface textures, ranging from fine nanoscale ripples to rougher microtextures such as microgrooves, spikes, and holes, on stainless steel AISI 304, copper, and the titanium alloy Ti64. PECVD coatings, including thin layers of glass and polymers, were subsequently applied to these textures to modulate surface chemistry and achieve the desired wettability.The results demonstrate that superhydrophilic surfaces with a water contact angle θ < 10° were achieved by combining rough textures with thin glass coatings, offering long-term stability that could be simply renewed via ultrasonic cleaning. Conversely, superhydrophobic surfaces with a water contact angle θ > 150° were instantly obtained using polymer coatings on rough textures. These functionalized surfaces also exhibited exceptional liquid repellence for complex liquids, such as milk and beer, making them particularly suitable for special applications using solutions or emulsions. The integration of laser texturing and PECVD coating provides a versatile and simple pathway for fabricating functional surfaces with tunable wettability and long-term performance across multiple metals and fluids.Item Open Access Hydrogele aus Polyethylenglykol und methacryloylierter Gelatine für biosensorische Oberflächen(2024) Grübel, Jana; Tovar, Günter E. M. (Prof. Dr.)Item Open Access Unravelling parameter interactions in calcium alginate/polyacrylamide double network hydrogels using a design of experiments approach for the optimization of mechanical properties(2024) Gorke, Oliver; Stuhlmüller, Marc; Tovar, Günter E. M.; Southan, AlexanderCalcium alginate/polyacrylamide double network hydrogels were reported to be exceptionally tough. However, literature reports so far varied the sample compositions mainly by one parameter at a time approaches, thus only drawing an incomplete picture of achievable material properties. In this contribution, sample compositions are varied according to a face-centered central composite experimental design taking into account the four parameters of alginate concentration cAlg, high/low molar mass alginate mixing ratio RP, acrylamide concentration cAAm, and N,N′-methylenebisacrylamide concentration cMBA. Each sample composition is investigated in triplicate. Thus, 75 samples were investigated by tensile testing, and a detailed analysis of the significant parameters and parameter interactions influencing the mechanical properties is conducted. The data shows that two parameter interactions, involving all four tested parameters, have a large effect on the Young's modulus, the strength, the toughness and the strain at material failure. As a consequence, it becomes evident that the experimental procedure from previous studies did not always result in optimum sample compositions. The results allow optimization of the mechanical properties within the studied parameter space, and a new maximum value of the strength of 710 kPa is reported. The data also give rise to the assumption that other parameters and parameter interactions ignored also in this study may allow further tailoring of mechanical properties.Item Open Access Microwave absorption of layer materials(2026) Hentrich, Andreas; Tovar, Günter E. M. (Prof. Dr.)The influence of the production process of atmospheric plasma sprayed ceramic coatings on the resonant absorption of millimeter waves was investigated. The main focus of the work was the application of these coatings as microwave absorbers in nuclear fusion related experiments. The production and optimization process for these absorbers was described in detail and most practically relevant parameter dependencies were investigated both in experiment and model.Item Open Access Life cycle assessment as a driver for process optimisation of cellobiose lipids fermentation and purification(2024) Oraby, Amira; Briem, Ann-Kathrin; Bippus, Lars; Rupp, Steffen; Zibek, SusannePurpose: Cellobiose lipids (CL) are biosurfactants produced by various Ustilaginaceae species in aerobic fermentations. They show high potential for application as alternatives to conventional oleochemical- or petrochemical surfactants. To ensure their environmentally friendly performance, we aimed to assess CL production from a life cycle perspective at an early developmental stage to identify process steps that have the highest impact on the environment. With this information, optimisation approaches can be derived.
Materials and methods: Following a cradle-to-gate approach, we modelled the CL fermentation and purification process based on experimental data from the lab scale and process simulation data at a 10 m 3 scale. For LCA, the impact categories (IC) abiotic depletion potential (ADP), eutrophication potential, photochemical ozone creation potential, global warming potential, acidification potential, and the primary energy demand were calculated for all process steps. Based on the obtained results, process bottlenecks were identified, and alternative process scenarios varying the related process parameters were simulated. These were used to assess the environmental impact reduction potential (EIRP) of an optimised process and draw recommendations for experimental process optimisation.
Results and discussion: The obtained results showed that the fermentation caused ~ 73% of ADP and more than 85% of all other ICs. The major contributor was the electricity consumption for continuous fermenter aeration. Thus, reducing the fermentation duration from the initial 14 to 5 days would result in a decrease in all investigated ICs of up to ~ 27-52%. An increase in CL concentration results in a decrease in all ICs of a similar magnitude due to the higher yield per batch at comparable energy and material consumption. Although the share of purification process steps to all ICs is overall relatively small, implementing foam fractionation for in situ product recovery showed an additional EIRP of 18-27% in all purification IC shares.
Conclusions: The conducted LCA showed that overall, more EIRP can be achieved by optimising fermentation process parameters compared to purification process steps. This is mainly due to the long fermentation duration and large energy consumption for fermenter aeration. This highlights the importance of using LCA as a driver for process optimisation to identify process steps with high EIRP. While some of the results are specific to CL, other obtained results can be transferred to other fermentations.Item Open Access Investigation of methacryloyl‐modified gelatin‐based hydrogels for inkjet‐printed biosensors and their adherence to polyethylene terephthalate and oriented polypropylene substrates(2026) Trust, Caroline M.; Lehmann, Regina M.; Schmidt, Sarah; Singer, Verena; Baum, Dominic; McBeth, Christine; Weber, AchimThe COVID‐19 pandemic has highlighted the need for rapid, simple, and cost‐effective point‐of‐care testing (POCT) methods for pathogen detection. Hydrogel‐based biosensing has emerged as an increasingly popular approach, offering advantages such as reagent storage and multiplexing capabilities. In this study, we have functionalized different polymer substrates to ensure an adequate adherence of methacryloyl‐modified gelatin‐based hydrogel spots that function as biosensors. Different hydrogel formulations were tested for their suitability in a point‐of‐care testchip. Our findings demonstrate the good adherence properties of amino‐functionalized and subsequent methacrylated polymer materials, specifically polyethylene terephthalate (PET) and oriented polypropylene (OPP), when used as substrates for hydrogel biosensors. Moreover, we successfully identified an optimal formulation for the hydrogel ink, consisting of amino‐functionalized methacryloyl‐modified gelatin with a biopolymer content of 3.5% (w/w) and a photoinitiator content of 0.0875%. This formulation not only enables printing with a piezoelectric 2D printer but also exhibits excellent hydrogel stability and adherence to the functionalized substrates. These results contribute to the development of reliable and efficient POCT methods for pathogen detection, addressing the limitations of current diagnostic capabilities. The study emphasizes inkjet‐based functionalization, with comprehensive characterization of printability including viscosity, surface tension, and density, and provides expanded methodological details to ensure reproducibility. Practical application : This study demonstrates the successful functionalization of PET and OPP polymers as substrates for point‐of‐care test chips, paving the way for advanced diagnostic solutions. By amino‐functionalization and methacryloylation of the surfaces, covalent bonding with biosensors was achieved, ensuring stability and adherence. A methacryloyl‐modified gelatin‐based hydrogel ink, optimized for piezoelectric printing, was identified for biosensor fabrication. The selected ink minimizes fluorophore quenching, preserving biosensor sensitivity. Among the tested materials, OPP showed superior adherence due to its non‐polar characteristics. These findings enable the creation of multiplexed test chips capable of detecting multiple pathogens simultaneously, addressing a crucial gap in rapid and reliable diagnostics. Although the hydrogel‐based biosensors have not yet been tested with encapsulated LAMP, this integration marks the next step toward fully functional point‐of‐care testing. Ultimately, this research advances the development of robust diagnostic platforms, with applications in healthcare settings for timely pathogen identification and disease management.Item Open Access Foam control in biotechnological processes : challenges and opportunities(2024) Tiso, Till; Demling, Philipp; Karmainski, Tobias; Oraby, Amira; Eiken, Jens; Liu, Luo; Bongartz, Patrick; Wessling, Matthias; Desmond, Peter; Schmitz, Simone; Weiser, Sophie; Emde, Frank; Czech, Hannah; Merz, Juliane; Zibek, Susanne; Blank, Lars M.; Regestein, LarsFoam formation is a massive challenge in submerged aerated bioprocesses, e.g., in beer fermentation. While the use of antifoam may easily overcome foaming at laboratory scale, it is often an unattractive solution since the challenge remains in future upscaling, as reduced mass transfer and extra steps in product purification and analytics result in increased costs. Interestingly, the number of studies tackling this challenge is relatively low, although literature suggests a range of alternatives, from avoiding foaming to means of controlling or even using foaming as an in situ product removal. Here we give an overview of the topic in five subsections. (1) We argue that a sound understanding of the molecular origin of foaming can facilitate solutions for overcoming the challenge while introducing some long-known challenges (i.e., in beer fermentation). We then review in (2) the apparent avoidance of foam formation before we in (3) summarize possibilities to reduce and control foam after its formation. Subsequently, in (4), we discuss possible solutions that take advantage of foam formation, for example, via foam fractionation for in situ product removal. Finally, in (5), we provide an overview of microbial strain engineering approaches to cope with some aspects of foaming in fermentations. With this review, we would like to sensitize and inform the interested reader while offering an overview of the current literature for the expert, particularly with regard to the foam special issue in Discover Chemical Engineering.Item Open Access Produktion von Beta-Glucanen mit Mikroalgen in geschlossenen Photobioreaktoren(2025) Frick, Konstantin; Tovar, Günter E. M. (Prof. Dr.)Item Open Access Ökobilanz für die Bioprozessoptimierung : Herstellung des Biotensids MEL(2024) Bippus, Lars; Briem, Ann-Kathrin; Beck, Alexander; Zibek, Susanne; Albrecht, StefanThis study evaluates the environmental impacts of producing mannosylerythritol lipids (MELs) using life cycle assessment (LCA) and kinetic models. MELs are microbial biosurfactants with various applications produced from biobased sources. The LCA results indicate that substrate provision, bioreactor aeration and solvent use for purification are major environmental impact sources. The findings highlight areas for improving the environmental sustainability of the production processes.