Institut für Lebensmittelwissenschaft und Biotechnologie

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Secretion of the cytoplasmic and high molecular weight β-galactosidase of Paenibacillus wynnii with Bacillus subtilis
(2024) Senger, Jana; Seitl, Ines; Pross, Eva; Fischer, Lutz
Background: The gram-positive bacterium Bacillus subtilis is widely used for industrial enzyme production. Its ability to secrete a wide range of enzymes into the extracellular medium especially facilitates downstream processing since cell disruption is avoided. Although various heterologous enzymes have been successfully secreted with B. subtilis, the secretion of cytoplasmic enzymes with high molecular weight is challenging. Only a few studies report on the secretion of cytoplasmic enzymes with a molecular weight > 100 kDa. Results: In this study, the cytoplasmic and 120 kDa β-galactosidase of Paenibacillus wynnii (β-gal-Pw) was expressed and secreted with B. subtilis SCK6. Different strategies were focused on to identify the best secretion conditions. Tailormade codon-optimization of the β-gal-Pw gene led to an increase in extracellular β-gal-Pw production. Consequently, the optimized gene was used to test four signal peptides and two promoters in different combinations. Differences in extracellular β-gal-Pw activity between the recombinant B. subtilis strains were observed with the successful secretion being highly dependent on the specific combination of promoter and signal peptide used. Interestingly, signal peptides of both the general secretory- and the twin-arginine translocation pathway mediated secretion. The highest extracellular activity of 55.2 ± 6 µkat/Lculture was reached when secretion was mediated by the PhoD signal peptide and expression was controlled by the PAprE promoter. Production of extracellular β-gal-Pw was further enhanced 1.4-fold in a bioreactor cultivation to 77.5 ± 10 µkat/Lculture with secretion efficiencies of more than 80%. Conclusion: For the first time, the β-gal-Pw was efficiently secreted with B. subtilis SCK6, demonstrating the potential of this strain for secretory production of cytoplasmic, high molecular weight enzymes.
Interactions between lipid oxidation and anthocyanins from black carrots in ω-3 fatty acid-rich flaxseed oil-in-water emulsions
(2024) Klinger, Evelyn; Salminen, Hanna; Bause, Karola; Weiss, Jochen
The application of anthocyanins as red colorants in lipid-containing foods such as oil-in-water emulsions is challenging due to their ability to act as antioxidants and their instability under various environmental conditions. In this study, we investigated the kinetics of black carrot anthocyanin degradation and the subsequent color loss influenced by lipid oxidation reactions in 1% ( w/w ) flaxseed oil-in-water emulsions stabilized by 0.1% ( w/w ) sodium dodecyl sulfate (SDS) at pH 2 upon storage at 35 °C for ten days under light and in the dark. Oxidatively stable Miglyol oil-in-water emulsions and SDS solutions were used as reference. The results showed simultaneous formation of lipid hydroperoxides and degradation of anthocyanins. The addition of anthocyanins decreased lipid hydroperoxide formation, confirming the antioxidant activity of anthocyanins through radical scavenging mechanism. The kinetic modelling of lipid oxidation and anthocyanin degradation are particularly important for estimating color stability in colored emulsion-based food systems such as dairy or non-dairy milk or yoghurt drinks.
Transforming agricultural waste from mediterranean fruits into renewable materials and products with a circular and digital approach
(2025) Castagna, Antonella; Aboudia, Aouatif; Guendouz, Amine; Scieuzo, Carmen; Falabella, Patrizia; Matthes, Julia; Schmid, Markus; Drissner, David; Allais, Florent; Chadni, Morad; Cravotto, Christian; Senge, Julia; Krupitzer, Christian; Canesi, Ilaria; Spinelli, Daniele; Drira, Fadoua; Ben Hlima, Hajer; Abdelkafi, Slim; Konstantinou, Ioannis; Albanis, Triantafyllos; Yfanti, Paraskevi; Lekka, Marilena E.; Lazzeri, Andrea; Aliotta, Laura; Gigante, Vito; Coltelli, Maria-Beatrice; Hilliou, Loic
The Mediterranean area is one of the major global producers of agricultural food. However, along the entire supply chain—from farming to food distribution and consumption—food waste represents a significant fraction. Additionally, plant waste residues generated during the cultivation of specific fruits and vegetables must also be considered. This heterogeneous biomass is a valuable source of bioactive compounds and materials that can be transformed into high-performance functional products. By analyzing technical and scientific literature, this review identifies extraction, composite production, and bioconversion as the main strategies for valorizing agricultural by-products and waste. The advantages of these approaches as well as efficiency gains through digitalization are discussed, along with their potential applications in the Mediterranean region to support new research activities and bioeconomic initiatives. Moreover, the review highlights the challenges and disadvantages associated with waste valorization, providing a critical comparison of different studies to offer a comprehensive perspective on the topic. The objective of this review is to evaluate the potential of agricultural waste valorization, identifying effective strategies while also considering their limitations, to contribute to the development of sustainable and innovative solutions in Mediterranean bioeconomy.
Synthesis of biologically active Shiga toxins in cell-free systems
(2024) Ramm, Franziska; Kaser, Danny; König, Irina; Fellendorf, Juliane; Wenzel, Dana; Zemella, Anne; Papatheodorou, Panagiotis; Barth, Holger; Schmidt, Herbert
Shiga toxins (Stx) produced by pathogenic bacteria can cause mild to severe diseases in humans. Thus, the analysis of such toxins is of utmost importance. As an AB5 toxin, Stx consist of a catalytic A-subunit acting as a ribosome-inactivating protein (RIP) and a B-pentamer binding domain. In this study we synthesized the subunits and holotoxins from Stx and Stx2a using different cell-free systems, namely an E. coli- and CHO-based cell-free protein synthesis (CFPS) system. The functional activity of the protein toxins was analyzed in two ways. First, activity of the A-subunits was assessed using an in vitro protein inhibition assay. StxA produced in an E. coli cell-free system showed significant RIP activity at concentrations of 0.02 nM, whereas toxins synthesized in a CHO cell-free system revealed significant activity at concentrations of 0.2 nM. Cell-free synthesized StxA2a was compared to StxA2a expressed in E. coli cells. Cell-based StxA2a had to be added at concentrations of 20 to 200 nM to yield a significant RIP activity. Furthermore, holotoxin analysis on cultured HeLa cells using an O-propargyl-puromycin assay showed significant protein translation reduction at concentrations of 10 nM and 5 nM for cell-free synthesized toxins derived from E. coli and CHO systems, respectively. Overall, these results show that Stx can be synthesized using different cell-free systems while remaining functionally active. In addition, we were able to use CFPS to assess the activity of different Stx variants which can further be used for RIPs in general.
Hydration-induced reduction strategies of acrylamide in bakery products
(2025) Świacka, Jagoda; Jekle, Mario
Bread is a product made from cereals and/or cereal-based ingredients, which are combined with water or other water-containing liquids. Also, additional ingredients such as oilseeds, legumes, potato products, dairy products, spices, and vegetables may be incorporated into the dough. Products containing these ingredients can be referred to as special bakery products. However, the use of these additional ingredients has been raising food-safety concerns, particularly because of the possibly elevated levels of acrylamide detected in the final products. Acrylamide is a process contaminant, considered undesirable due to its potential carcinogenicity and is currently subject to various European food safety regulations. However, the acrylamide mitigation strategies defined so far for standard bakery products do not appear to be sufficiently effective for special bakery products. This is presumably due to the high levels of precursor molecules and the varying quality of the special ingredients. As a result, there are large variations in the levels of precursors, namely reducing sugars and asparagine in the dough, which consequently lead to unpredictably elevated acrylamide contamination. To address these problems and to gain a deeper understanding of acrylamide formation in special bakery products, further investigation is essential. Therefore, this thesis aimed to identify specific acrylamide precursors, to analyze acrylamide levels, and to assess the effectiveness of hydration-based approaches as mitigation measures for special bakery products. Mitigation was to be achieved either by eliminating the precursors or by adjusting processing conditions. After a theoretical introduction in Chapter I, a systematic investigation of two special ingredients, with a focus on their specific acrylamide precursors, was presented in Chapter II and Chapter III. Particular attention was drawn to potato flakes, known for their high asparagine content, and carrot strips, awaited to be high in reducing sugars. The effects of these ingredients in combination with varying water additions as hydration approach, were investigated using a model dough recipe. The model dough consisted of wheat flour type 550, water, NaCl, yeast and selected special ingredients. After baking, both bread crust and crumb were analyzed for acrylamide and in parallel, baking qualities of these bakery products were evaluated. Considering acrylamide contamination, increased water addition showed highly raw material-specific effects. In high-asparagine doughs, higher dough water addition tended even to increase acrylamide formation, presumably due to enhanced mobility of precursors. Interestingly, for the carrot-based doughs, the polyphenols emerged as a potential factor significantly reducing acrylamide formation at higher water additions, highlighting their relevance for future mitigation strategies. Due to the significant differences in the qualities of available carrot strips, shown in Chapter III, Chapter IV described the effects of origin, processing and drying methods on different quality features of dried carrot strips. For that, three carrot varieties were purchased and processed. Processing steps included blanching and drying methods, such as hot-air drying, vacuum drying, or freeze-drying. The impact of each processing method on quality of carrot strips, their acrylamide-forming potential, and the resulting acrylamide levels in model bakery products was analyzed. Blanching in particular, significantly reduced the acrylamide formation potential of the carrot strips. Freeze-drying consistently resulted in the highest concentrations of sugars, free asparagine, and β‑carotene for all carrot varieties, whereas the retainment of these compounds was inconsistent with other drying methods. Asparagine levels during storage were shown to fluctuate, with an initial increase and a following decrease, underlining the importance of timed processing to warrant constant product quality. Overall, the potential of carrot strips for acrylamide formation depended mostly on their variety and storage conditions, which determined primarily their precursor profile. To investigate a variety-unspecific acrylamide mitigation strategy, soaking was evaluated in Chapter V as an approach for products with dried carrot strips. Additionally, ultrasound-assisted rehydration was investigated as a method to enhance the diffusion of carrot matrix constituents. Regular soaking was compared with ultrasound-assisted rehydration (ultrasonic bath or sonotrode) regarding rehydration rate and leaching of sugars from the carrot strips. The kinetics of rehydration and diffusion were modelled using the ExpAssoc and the Peleg equations. Rehydrated carrot strips were then implemented in model breads and acrylamide concentration in the crust along with baking qualities were analyzed. Overall, longer rehydration led to higher water retention in the carrot strips and increased leaching of sugars and polyphenols. Both ultrasound-assisted rehydration and regular soaking led to reduced acrylamide levels in model breads up to 75%. Summarizing, this thesis systematically examined the addition of potato flakes and carrot strips to bakery products, identifying their critical acrylamide precursors, expected acrylamide levels, and characteristic changes in bread quality. It proved that rehydration is an effective acrylamide mitigation strategy for special bakery products, primarily by promoting precursor leaching and influencing reaction conditions. Overall, this thesis provides guidance on the target raw material qualities and presents (easy-to-apply) mitigation approaches for various manufacturers.
On the structural analysis and optimal input design for joint state and parameter estimation
(2025) Lepsien, Arthur; Kügler, Philipp; Schaum, Alexander
This paper addresses the problem of joint state and parameter estimation for nonlinear affine-input systems with positive parameters including the design of a closed-loop optimal input adaptation to increase an identifiability measure for the system. The identifiability itself is considered in the context of structural observability of the system dynamics based on structural analysis of the system including the unknown parameters as additional states. In particular, the network graph-based interpretation of structural observability is employed at this point. This analysis motivates to include time derivatives of the measurements as additional system outputs to enhance the structural observability properties. For this purpose robust exact differentiation is considered, relying on the super-twisting algorithm to obtain finite time convergent estimates of these signals. Using the extended measurement signal, a continuous-discrete Extended Kalman filter is proposed that ensures strictly positive estimates for the parameters. Based on the estimates of states and parameters the input signal is determined using a moving horizon optimal predictive control that evaluates the condition number of the Fisher information matrix, thus maximizing the information content of the measurements with respect to the parameters. The proposed scheme extends and combines different previously discussed approaches from the literature and is evaluated by means of a thermal process example in simulation and experiment, showing high potential for similar system identification problems.
Sustainability certification in the digital era: a qualitative analysis of sustainability reports across product categories
(2026) Boller, Meta Leonie; Grabinger, Toni; Zurwehme, Annikka; Krupitzer, Christian
The food industry faces growing pressure to align sustainability goals with the rapid advance of digital technologies. This study explores how digitalization supports and transforms sustainability certification practices across diverse food product categories. Novelty lies in examining the interplay between digital technologies and sustainability reporting intensity, offering insights into how firms communicate and operationalize sustainability commitments. A qualitative content analysis was conducted on the sustainability reports of 21 companies using MAXQDA software, assessing the frequency and depth of reporting on sustainability focus topics and digital tools applied. The study includes multiple food product categories, such as coffee and tea, chocolate, grain products, dairy products, beverages, meat and fish, and tropical fruits. Results show that larger firms and those with higher turnover report more frequently and comprehensively on sustainability and digitalization. Three clusters of companies were identified, each reflecting shared sustainability challenges rather than specific product categories. The findings suggest that the relevance of digital technologies is more closely linked to addressing these cross-cutting sustainability challenges, and that high-value product segments provide the most promising starting points for integrating digital technologies into certification processes.
Monitoring a coffee roasting process based on near‐infrared and raman spectroscopy coupled with chemometrics
(2025) Munyendo, Leah; Schuster, Katharina; Armbruster, Wolfgang; Babor, Majharulislam; Njoroge, Daniel; Zhang, Yanyan; von Wrochem, Almut; Schaum, Alexander; Hitzmann, Bernd
Roasting is a fundamental step in coffee processing, where complex reactions form chemical compounds related to the coffee flavor and its health‐beneficial effects. These reactions occur on various time scales depending on the roasting conditions. To monitor the process and ensure reproducibility, the study proposes simple and fast techniques based on spectroscopy. This work uses analytical tools based on near‐infrared (NIR) and Raman spectroscopy to monitor the coffee roasting process by predicting chemical changes in coffee beans during roasting. Green coffee beans of Robusta and Arabica species were roasted at 240°C for different roasting times. The spectra of the samples were taken using the spectrometers and modeled by the k‐nearest neighbor regression (KNR), partial least squares regression (PLSR), and multiple linear regression (MLR) to predict concentrations from the spectral data sets. For NIR spectra, all the models provided satisfactory results for the prediction of chlorogenic acid, trigonelline, and DPPH radical scavenging activity with low relative root mean square error of prediction (pRMSEP < 9.649%) and high coefficient of determination ( R 2 > 0.915). The predictions for ABTS radical scavenging activity were reasonably good. On the contrary, the models poorly predicted the caffeine and total phenolic content (TPC). Similarly, all the models based on the Raman spectra provided good prediction accuracies for monitoring the dynamics of chlorogenic acid, trigonelline, and DPPH radical scavenging activity (pRMSEP < 7.849% and R 2 > 0.944). The results for ABTS radical scavenging activity, caffeine, and TPC were similar to those of NIR spectra. These findings demonstrate the potential of Raman and NIR spectroscopy methods in tracking chemical changes in coffee during roasting. By doing so, it may be possible to control the quality of coffee in terms of its aroma, flavor, and roast level.
From spectra to traits: advancements in predicting wheat characteristics
(2025) Nagel-Held, Johannes Henrich; Hitzmann, Bernd
This thesis is driven by two primary objectives: To evaluate the potential for improving quality assessment throughout the wheat value chain and the potential for replacing protein content as the primary determinant of price and quality with spectroscopic methods. An early, fast, and well-founded decision on wheat quality leads to improved processing properties and product quality of wheat products. Given that these attributes are often more closely tied to protein quality or other components than protein quantity, a direct and precise quantification is highly desirable. The noteworthy advantage of protein content lies in its prediction through near-infrared spectroscopy (NIRS). To augment the information available from near-infrared spectra, which are inherently limited in their insights into molecular compounds within samples, NIRS was supplemented with Raman and fluorescence spectroscopy. The thesis`s foundation comprises four distinct sample sets, encompassing both common wheat and spelt. In total, a staggering 4,237 samples of whole grain, whole grain flour, and extracted flour were analyzed to predict a wide array of 100 diverse quality parameters, spanning from measures of protein quality to dough rheological properties, baking behavior, physical and chemical characteristics and agronomic traits. To enable accurate predictions several spectra pre-processing and regression techniques were applied. Among the spectrometers and algorithms tested, no clear recommendation can be given. In this work, NIRS was found to perform well over different levels of sample preparation, while Raman and fluorescence spectroscopy performed better on flour. A glimpse into the findings is best exemplified by considering loaf volume, a measure of end-product quality. Prediction errors (RMSECV) ranged between 29 and 43 mL/100 g of flour, accompanied by R² values spanning 0.66 to 0.78. One major factor influencing the improvable prediction accuracy is the inherent measurement error associated with the baking trial. However, when this measurement error is known, a straightforward solution emerges: By measuring a few samples repeatedly, the prediction error can be corrected from 43 mL/100 g of flour to 28 mL/100 g, aligning with the magnitude of the measurement error itself. Simultaneously, the corrected R² value improves from 0.66 to 0.86. It has been shown that measurement error correction works for other quality characteristics, such as water absorption or baking loss, and may be applied to other parameters. The robustness of the models was evaluated by successfully predicting complex traits of unknown cultivars. However, the models proved less effective in predicting across separate locations and years. Similar robustness results were found for protein content, water absorption and grain yield. Since protein content is a well-established and predictable parameter, robust models for complex traits are also feasible. Other well predictable parameters are protein content (R² = 0.97-0.98, RMSECV = 0.16-0.20 %), wet gluten content (R² = 0.89-0.98, RMSECV = 0.80-0.84 %), water absorption (R² = 0.68-0.83, RMSECV = 0.9-1.2 mL/100 g) and grain yield (R² = 0.73-0.85, RMSECV = 5.9-6.8 dt/ha). Examples for non-predictable parameters are starch properties measured with a rapid visco analyzer or enzyme activity. And for some parameters no clear conclusion could be drawn, such as SDS sedimentation volume, plant height, thousand kernel weight, extensograph or farinograph parameters. The successful prediction of intricate traits can be further refined by reducing measurement errors of the reference values and using better suited spectrometers. The robustness can be increased by expanding the sample set by including data from a broader spectrum of locations and years.Implementing this proposed methodology holds the potential to instigate positive changes within the wheat supply chain, with implications for product quality, environment, and economic aspects.
Storable cheese curd—effect of milk homogenization as a pre-treatment and freezing and extrusion of cheese curd on production of pasta filata style cheese
(2024) Schmidt, Florian; Graf, Britta; Hinrichs, Jörg
This study investigates the production of pasta filata style cheese from a storable, frozen intermediate material. Homogenization (2–16 MPa, single-staged) of milk (fat/protein = 0.9) was used as a tool to decrease fat globule size and consequently fat losses. Plasticization was achieved by using a single-screw extruder set up with double-jacketed hot water cycle. Non-frozen and frozen cheese curd as well as the extruded pasta filata style cheese pre-treated with different homogenization pressure was analyzed regarding the thermo-rheological properties. Fat and protein gain/loss during extrusion was evaluated by analyzing fat in dry matter (FDM) and protein in dry matter (PDM) before and after extrusion. Homogenization of cheese milk leads to a reduction of tan δ for thereof produced raw cheese curd material as well as the extruded products. Freezing and extrusion counteract the reduction of tan δ . A homogenization pressure of 8 MPa is sufficient to prevent fat losses during extrusion while still maintaining plasticization of the product for fresh and frozen material, respectively. The FDM after extrusion is 0.8% higher for fresh material and 4.9% higher for frozen material, which means that the fat concentrates during extrusion due to water loss. Moreover, there is no loss of PDM for all samples, regardless of the homogenization pressure. A combination of homogenization pressure, freezing, and extrusion leads to a plasticizable product without losses of fat and protein. Hence, frozen cheese curd can be used as a storable intermediate.
Comparative assessment of ethanol production from six typical German waste baked products
(2024) Almuhammad, Mervat; Kölling, Ralf; Einfalt, Daniel
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.
Poultry perfection : comparison of computer vision models to detect and classify poultry products in a production setting
(2025) Einsiedel, Daniel; Vita, Marco; Jox, Dana; Dunnewind, Bertus; Meulendijks, Johan; Krupitzer, Christian
This study explores the use of computer vision, specifically object detection, for quality control in ready-to-eat meat products. We focused on a single process step, labeling products as “good” or “imperfect”. An “imperfect product” constitutes a product that deviates from the norm regarding shape, size, or color (having a hole, missing edges, dark particles, etc.). Imperfect does not mean the product is inedible or a risk to food safety, but it affects the overall product quality. Various object detectors, such as YOLO, including YOLO12, were compared using the mAP50-95 metric. Most models achieved mAP scores over 0.9, with YOLO12 reaching a peak score of 0.9359. The precision and recall curves indicated that the model learned the “imperfect product” class better, most likely due to its higher representation. This underscores the importance of a balanced dataset, which is challenging to achieve in real-world settings. The confusion matrix revealed false positives, suggesting that increasing dataset volume or hyperparameter tuning could help. However, increasing the dataset volume is usually the more difficult path since data acquisition and especially labeling are by far the most time-consuming steps of the whole process. Overall, current models can be applied to quality control tasks with some margin of error. Our experiments show that high-quality, consistently labeled datasets are potentially more important than the choice of the model for achieving good results. The applied hyperparameter tuning on the YOLO12 model did not outperform the default model in this case. Future work could involve training models on a multi-class dataset with hyperparameter optimization. A multi-class dataset could contain more specific classes than just “good” and “imperfect,” making trained models capable of actually predicting specific quality deviations.
High-performance thin-layer chromatography for the detection of compositional changes in LACTEM emulsifiers during storage
(2025) Schuster, Katharina; Blankart, Max; Hinrichs, Jörg; Oellig, Claudia
Quality control of food emulsifiers, such as lactic acid esters of mono- and diacylglycerols (LACTEM), is crucial in the reproducible production of food products. The current study investigated compositional changes of LACTEM emulsifiers using high-performance thin-layer chromatography (HPTLC) during storage at 60 °C for 8 weeks. Ultraviolet (UV) and fluorescence images of the HPTLC silica gel F254s plates after primuline derivatization and densitometric data were analyzed to assess changes in the composition. Significant changes were observed for minor LACTEM components (< 10% relative intensity), specifically a decrease in higher-lactylated monoacylglycerols and an increase in triacylglycerols. Techno-functional properties, such as particle size distribution, apparent viscosity, overrun, foam firmness, drainage, and residual cream of aerosol whipping cream (0.8 g 100 g−1 LACTEM) were investigated. While emulsion stability was not affected, the foam firmness increased significantly, corresponding to a visibly more brittle foam. On the basis of these results, monitoring compositional changes in the food-manufacturing process is necessary to maintain constant food quality.
Spatial transcriptomics of a parasitic flatworm provides a molecular map of drug targets and drug resistance genes
(2024) Gramberg, Svenja; Puckelwaldt, Oliver; Schmitt, Tobias; Lu, Zhigang; Haeberlein, Simone
The spatial organization of gene expression dictates tissue functions in multicellular parasites. Here, we present the spatial transcriptome of a parasitic flatworm, the common liver fluke Fasciola hepatica . We identify gene expression profiles and marker genes for eight distinct tissues and validate the latter by in situ hybridization. To demonstrate the power of our spatial atlas, we focus on genes with substantial medical importance, including vaccine candidates (Ly6 proteins) and drug resistance genes (glutathione S-transferases, ABC transporters). Several of these genes exhibit unique expression patterns, indicating tissue-specific biological functions. Notably, the prioritization of tegumental protein kinases identifies a PKCβ, for which small-molecule targeting causes parasite death. Our comprehensive gene expression map provides unprecedented molecular insights into the organ systems of this complex parasitic organism, serving as a valuable tool for both basic and applied research.
Structure formation in fruit preparations by fruit fermentates produced with exopolysaccharide-forming lactic acid bacteria
(2025) Festini, Silvan; Zipori, Dor; Wallisch, Marc; Weiss, Agnes; Neidhart, Sybille; Schmidt, Herbert; Jekle, Mario
Fruit preparations are intermediate food products that are primarily used in the dairy industry for the production of fruit yogurt or frozen desserts. Typically, they are stabilized by added hydrocolloids like pectins. The objective of this study was to investigate the potential replacement of conventional stabilizers by structure-forming fermentates produced by exopolysaccharides (EPS)-forming lactic acid bacteria (LAB). Peach puree was selected as fermentation matrix. Prior to 72 h of incubation, it was inoculated with either the heterofermentative LAB strain Levilactobacillus brevis TMW 1.2112 or the homofermentative LAB strain Pediococcus parvulus strain LTH 1110, both being known to produce EPS in form of β-D-glucan. The lyophilized fermentates were applied as stabilizers to produce strawberry fruit preparations. Flow curves, viscoelastic behaviour and shear stability were measured to investigate the effect of fermentate incorporation on the rheological properties of the products. A fermentatively induced effect was observed in terms of a 1.3-fold increase in viscosity of strawberry model fruit preparations with 10 % fermentate of Lv. brevis TMW 1.2112 compared to the addition of the same dose of fermentate blank. Further, increasing the fermentate blank dose from 10 % to 15 % resulted in a 2.4-fold viscosity increase of the model fruit preparations. High shear stability was found in all model strawberry fruit preparations. However, fermentation had no clear benefit in terms of viscoelastic behaviour and shear stability of the fruit preparations. Although the fermentatively induced thickening potential was limited, production of viscosity-increasing peach fermentate with minor changes in the sugar and amino acid profiles of the fruit proved to be feasible.
Effect of smoldering air volume flow rates and smoking time on quality attributes of Frankfurter-type sausages
(2025) Leible, Malte; Herrmann, Kurt; Gibis, Monika; Weiss, Jochen
This study explores the effects of varying smoking conditions on the properties of Frankfurter-type sausages. Using a modified smoldering smoke generator, air volume flow rate and smoking time were varied to assess their impact on color, texture, and sensory characteristics. The results showed significant changes in these characteristics and a wide spectrum in smoke color was produced across the 14 different settings. L* values ranged from 64.32 ± 0.61 to 46.33 ± 0.78, a* values ranged from 11.81 ± 0.29 to 24.18 ± 0.39, b* values ranged from 14.93 ± 0.77 to 41.20 ± 1.25 with an increase in smoking time and air volume flow generally leading to a darker smoking color. Sensory test regarding color showed that the perceived color behaved similarly to the measured color. In these descriptive tests the perceived color ranged from 0.42 ± 0.42 to 9.67 ± 0.43 on a scale from 0 to 10. Smoke odor did not show the strong differences seen in the other results. Here the perceived smoke odor ranged from 4.76 ± 2.00 to 8.64 ± 1.03 on a scale from 0 to 10. Since the study was based on a statistical experimental plan, a predictive model based on a surface plot could be established. These findings provide valuable insights in the qualitative changes in Frankfurter -Type sausages for optimizing smoking parameters in the food industry, potentially enabling precise control over desired sensory and physical properties in smoked meat products.
Effect of liquefaction temperature and enzymatic treatment on bioethanol production from mixed waste baked products
(2025) Almuhammad, Mervat; Kölling, Ralf; Einfalt, Daniel
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.
Towards sustainable biointelligent food design: structuring potential of plant-based materials exemplified using apricot seed oil oleogels and bigels through 3D food printing
(2025) Reinmuth, Evelyn; Fahmy, Ahmed Raouf; Ribette, Olivia; Jekle, Mario
Background/Introduction: Biointelligence in the approach of food additive manufacturing represents a significant advancement, enabling the reverse engineering and design of foods. Legislation restricting trans-fats has accelerated research into alternatives, but ingredients like saturated and trans fats play key roles in food quality and functionality. Oleogels are a promising replacement. Food additive manufacturing introduces a biointelligent approach, combining biological and technical components with information technology to optimize food design. This study investigates 3D printing of oleogel and bigel systems using apricot seed oil, aiming to assess their significance, applicability, and printability as sustainable alternatives to trans fats for innovative, resource-efficient food production. Methods: Apricot seed oil, rich in antioxidants and polyunsaturated fatty acids, was processed into plant-based oleogels and bigels. The material systems were incorporated into 3D printed food structures. Material characterization and techno-functional analysis were conducted to evaluate the suitability of apricot seed oil for structuring 3D printed foods and controlling food texture. Results: Adjusting the type and concentration of oil-gelator mixtures enabled tailored texture and lipid distribution to fit consumer preferences. Sustainability impacts were assessed at intermediate processing steps, demonstrating the value of holistic evaluations beyond technical factors. Discussion: Biointelligent 3D printing offers a platform to optimize sensory and sustainability qualities in food design. The integration of apricot seed oil into novel food matrices enables versatile nutritional product development, supporting researchers and industry stakeholders in advancing consumer-centric, sustainable production and consumption practices.
A diamine oxidase from Glutamicibacter halophytocola for the degradation of histamine and tyramine in foods
(2025) Kettner, Lucas; Freund, Alexander; Bechtel, Anna; Costa-Catala, Judit; Fischer, Lutz
A novel diamine oxidase (DAO) was discovered in the bacterium Glutamicibacter halophytocola (DAO-GH). The gene of DAO-GH was integrated into the genome of the yeast Komagataella phaffii and recombinantly produced under control of the methanol-inducible AOX1 promoter in a bioreactor cultivation. A high DAO activity of 70.2 ± 5.2 µkat/Lculture (5.25 ± 0.22 µkat/gprotein) was yielded after 90 h of cultivation. The DAO-GH was partially purified by the polyethyleneimine precipitation of nucleic acids, fractionated ammonium sulfate precipitation and hydrophobic interaction chromatography, resulting in a specific DAO activity of 19.7 µkat/gProtein. The DAO-GH was then biochemically investigated regarding its potential for histamine and tyramine degradation in fermented foods and the human small intestine. Interestingly, the DAO-GH showed activity even at a low pH of 5 and low temperature of 6 °C. Both histamine and tyramine were effectively degraded and DAO-GH showed especially very high affinity towards tyramine (Km of 0.009 mM). The DAO-GH was shown to be capable of degrading around 20% of the initially applied histamine in tuna paste (pH 5.6) at 5 °C within 24 h and completely degraded the histamine in a simulated intestinal fluid within 1.5 h in bioconversion experiments. The DAO-GH was spray-dried for the production of a storable enzyme preparation. Only around 17% of activity were lost in this process and the DAO-GH remained stable at room temperature for at least 3 months. The discovery of this DAO with its very advantageous biochemical properties allows the preparation of histamine-reduced or -free fermented foods by a simple enzymatic treatment or the treatment of histamine intolerance symptoms as a dietary supplement or medicine.
Recombinant production of Paenibacillus wynnii β-galactosidase with Komagataella phaffii
(2024) Bechtel, Anna; Seitl, Ines; Pross, Eva; Hetzel, Frank; Keutgen, Mario; Fischer, Lutz
The β-galactosidase from Paenibacillus wynnii (β-gal-Pw) is a promising candidate for lactose hydrolysis in milk and dairy products, as it has a higher affinity for the substrate lactose (low KM value) compared to industrially used β-galactosidases and is not inhibited by the hydrolysis-generated product D-galactose. However, β-gal-Pw must firstly be produced cost-effectively for any potential industrial application. Accordingly, the yeast Komagataella phaffii was chosen to investigate its feasibility to recombinantly produce β-gal-Pw since it is approved for the regulated production of food enzymes. The aim of this study was to find the most suitable way to produce the β-gal-Pw in K. phaffii either extracellularly or intracellularly.ResultsFirstly, 11 different signal peptides were tested for extracellular production of β-gal-Pw by K. phaffii under the control of the constitutive GAP promoter. None of the signal peptides resulted in a secretion of β-gal-Pw, indicating problems within the secretory pathway of this enzyme. Therefore, intracellular β-gal-Pw production was investigated using the GAP or methanol-inducible AOX1 promoter. A four-fold higher volumetric β-galactosidase activity of 7537 ± 66 µkatoNPGal/Lculture was achieved by the K. phaffii clone 27 using the AOX1 promoter in fed-batch bioreactor cultivations, compared to the clone 5 using the GAP promoter. However, a two-fold higher specific productivity of 3.14 ± 0.05 µkatoNPGal/gDCW/h was achieved when using the GAP promoter for β-gal-Pw production compared to the AOX1 promoter. After partial purification, a β-gal-Pw enzyme preparation with a total β-galactosidase activity of 3082 ± 98 µkatoNPGal was obtained from 1 L of recombinant K. phaffii culture (using AOX1 promoter).ConclusionThis study showed that the β-gal-Pw was produced intracellularly by K. phaffii, but the secretion was not achieved with the signal peptides chosen. Nevertheless, a straightforward approach to improve the intracellular β-gal-Pw production with K. phaffii by using either the GAP or AOX1 promoter in bioreactor cultivations was demonstrated, offering insights into alternative production methods for this enzyme.

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