Fakultät Naturwissenschaften

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Biologie, Ernährungs-wissenschaften und Lebensmittelwissenschaften sind die Schwerpunkte der Fakultät. Die Forschung befasst sich mit Schlüsselthemen der Life Sciences.

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Now showing 1 - 4 of 4

Comparative assessment of ethanol production from six typical German waste baked products
(2024) Almuhammad, Mervat; Kölling, Ralf; Einfalt, Daniel; Almuhammad, Mervat; Yeast Genetics and Fermentation Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 23, 70599, Stuttgart, Germany; Kölling, Ralf; Yeast Genetics and Fermentation Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 23, 70599, Stuttgart, Germany; Einfalt, Daniel; Yeast Genetics and Fermentation Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 23, 70599, Stuttgart, Germany
This study investigates the potential for bioethanol production of six types of typical German leftover baked products: bread rolls, pretzel rolls, fine rye bread, white bread, pastry, and cream cakes. The experimental setup consisted of two experiments—one as a control and another with the addition of diammonium phosphate (DAP) to the mash. In terms of monosaccharide concentration at 30% dry matter (DM), white bread mash exhibited the highest level at 251.5 g/L, while cream cakes mash had the lowest at 186 g/L. The highest ethanol production occurred after 96 h of fermentation with rye bread, yielding 78.4 g/L. In contrast, despite having the highest monosaccharide levels, white bread produced only 21.5 g/L of ethanol after 96 h. The addition of DAP accelerated monosaccharide consumption in all baked products, with cream cakes completing the process in just 24 h. Bread rolls, pretzel rolls, pastry, and white bread fermentations finished within 72 h. Ethanol yields significantly increased in three DAP samples, with pretzel rolls yielding the highest ethanol concentration at 98.5 g/L, followed by white bread with 90.6 g/L, and bread rolls with 87.7 g/L. DAP had a substantial impact on all samples, reducing fermentation time and/or increasing ethanol yield. This effect was particularly pronounced with white bread, where it improved conversion efficiency from 17 to 72%, resulting in 90.6 g/L of ethanol. These results demonstrate that waste baked products hold substantial potential for bioethanol production, and this potential can be further enhanced through the addition of DAP.
Effect of liquefaction temperature and enzymatic treatment on bioethanol production from mixed waste baked products
(2025) Almuhammad, Mervat; Kölling, Ralf; Einfalt, Daniel; Almuhammad, Mervat; Yeast Genetics and Fermentation Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 23, 70599, Stuttgart, Germany; Kölling, Ralf; Yeast Genetics and Fermentation Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstraße 23, 70599, Stuttgart, Germany; Einfalt, Daniel; Botanical Garden, Ulm University, Hans-Krebs-Weg, 89081, Ulm, Germany
This study investigates the effect of different liquefaction temperatures (50–70 °C) and four commercial enzyme formulations on glucose release and subsequent ethanol yield, using mixed waste baked products as a substrate. Among the enzymes tested, Amylase GA 500 proved to be superior in the hydrolysis of starch at lower temperatures (50 °C and 55°C). At higher liquefaction temperatures (65 °C and 70°C) all four enzyme preparations showed comparable activity. The highest glucose concentration (205.7 g/L) and the highest ethanol yield (92 g/L) were achieved with Amylase GA 500 at 65 °C. Its superior performance is attributed to the synergistic activity of α-amylase and glucoamylase, which facilitates efficient starch hydrolysis. Crucially, we discovered that the liquefaction temperature profoundly affects fermentation speed independently of the initial glucose concentration or the enzyme preparation used for starch hydrolysis. This novel mechanistic insight suggests that higher temperature treatment either makes an additional factor crucial for yeast fermentation available or depletes/destroys an inhibitor present in the complex waste bakery product matrix. These findings highlight the critical role of temperature and enzyme formulation in optimizing bioethanol production from bakery waste, supporting the development of more sustainable and efficient waste-to-biofuel processes.
Experimental investigation of CO2 uptake in CO2 hydrates formation with amino acids as kinetic promoters and its dissociation at high temperature
(2022) Srivastava, Shubhangi; Kollemparembil, Ann Mary; Zettel, Viktoria; Claßen, Timo; Gatternig, Bernhard; Delgado, Antonio; Hitzmann, Bernd
The dissociation of CO2 gas hydrates (GH) with amino acid kinetic promoters and without promoters was studied at a high temperature of 90 °C for a period of 20 min to understand the percentage of CO2 gas and to select the best promoter that aids CO2 gas entrapment along with stability at a high temperature. The possibility of using four hydrophobic food grade amino acids, namely cysteine, valine, leucine, and methionine, and one surfactant, lecithin, as kinetic promoters for CO2 GH has been studied. The amino acids were added 0.5 g (wt%), and lecithin was added 5 g for the GH production. Furthermore, the amino acids leucine and methionine gave some positive results, therefore, these amino acids were carried further for the experimentation purpose in the production of CO2 GH. Also, a combinational use of these amino acids was studied to investigate the effect on % CO2 retention in comparison to the normal GH. From the results, it was observed that the stability of GH decreases with an increase in temperature, but the addition of promoters, especially leucine + methionine + lecithin increased the CO2 uptake during GH formation.
Quantification of shear viscosity and wall slip velocity of highly concentrated suspensions with non-Newtonian matrices in pressure driven flows
(2021) Wilms, Patrick; Wieringa, Jan; Blijdenstein, Theo; van Malssen, Kees; Kohlus, Reinhard
The rheological characterization of concentrated suspensions is complicated by the heterogeneous nature of their flow. In this contribution, the shear viscosity and wall slip velocity are quantified for highly concentrated suspensions (solid volume fractions of 0.55–0.60, D4,3 ~ 5 µm). The shear viscosity was determined using a high-pressure capillary rheometer equipped with a 3D-printed die that has a grooved surface of the internal flow channel. The wall slip velocity was then calculated from the difference between the apparent shear rates through a rough and smooth die, at identical wall shear stress. The influence of liquid phase rheology on the wall slip velocity was investigated by using different thickeners, resulting in different degrees of shear rate dependency, i.e. the flow indices varied between 0.20 and 1.00. The wall slip velocity scaled with the flow index of the liquid phase at a solid volume fraction of 0.60 and showed increasingly large deviations with decreasing solid volume fraction. It is hypothesized that these deviations are related to shear-induced migration of solids and macromolecules due to the large shear stress and shear rate gradients.

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