Institut für Lebensmittelwissenschaft und Biotechnologie
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Publication Consumption of yeast-fermented wheat and rye breads increases colitis and mortality in a mouse model of colitis(2022) Zimmermann, Julia; De Fazio, Luigia; Kaden-Volynets, Valentina; Hitzmann, Bernd; Bischoff, Stephan C.; Zimmermann, Julia; Department of Nutritional Medicine/Prevention, University of Hohenheim, Stuttgart, Germany; De Fazio, Luigia; Department of Medical and Surgical Science (DIMEC), University of Bologna, Bologna, Italy; Kaden-Volynets, Valentina; Department of Nutritional Medicine/Prevention, University of Hohenheim, Stuttgart, Germany; Hitzmann, Bernd; Department of Process Analytics and Cereal Science, University of Hohenheim, Stuttgart, Germany; Bischoff, Stephan C.; Department of Nutritional Medicine/Prevention, University of Hohenheim, Stuttgart, GermanyBackground: Cereals are known to trigger for wheat allergy, celiac disease and non-celiac wheat sensitivity (NCWS). Inflammatory processes and intestinal barrier impairment are suspected to be involved in NCWS, although the molecular triggers are unclear. Aims: We were interested if different bread types influence inflammatory processes and intestinal barrier function in a mouse model of inflammatory bowel disease. Methods: Epithelial caspase-8 gene knockout (Casp8 ΔIEC ) and control (Casp8 fl ) mice were randomized to eight groups, respectively. The groups received different diets for 28 days (gluten-free diet, gluten-rich diet 5 g%, or different types of bread at 50 g%). Breads varied regarding grain, milling and fermentation. All diets were isocaloric. Results: Regardless of the diet, Casp8 ΔIEC mice showed pronounced inflammation in colon compared to ileum, whereas Casp8 fl mice were hardly inflamed. Casp8 fl mice could tolerate all bread types. Especially yeast fermented rye and wheat bread from superfine flour but not pure gluten challenge increased colitis and mortality in Casp8 ΔIEC mice. Hepatic expression of lipopolysaccharide-binding protein and colonic expression of tumor necrosis factor-α genes were inversely related to survival. The bread diets, but not the gluten-rich diet, also decreased colonic tight junction expression to variable degrees, without clear association to survival and inflammation. Conclusions: Bread components, especially those from yeast-fermented breads from wheat and rye, increase colitis and mortality in Casp8 ΔIEC mice highly susceptible to intestinal inflammation, whereas control mice can tolerate all types of bread without inflammation. Yet unidentified bread components other than gluten seem to play the major role.Publication Fed-batch bioreactor cultivation of Bacillus subtilis using vegetable juice as an alternative carbon source for lipopeptides production: a shift towards a circular bioeconomy(2024) Gugel, Irene; Vahidinasab, Maliheh; Benatto Perino, Elvio Henrique; Hiller, Eric; Marchetti, Filippo; Costa, Stefania; Pfannstiel, Jens; Konnerth, Philipp; Vertuani, Silvia; Manfredini, Stefano; Hausmann, Rudolf; Gugel, Irene; Department of Life Sciences and Biotechnology, University of Ferrara, 44121 Ferrara, Italy, (S.V.);; Vahidinasab, Maliheh; Department of Bioprocess Engineering (150k), Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstrasse 12, 70599 Stuttgart, Germany; (E.H.B.P.);; Benatto Perino, Elvio Henrique; Department of Bioprocess Engineering (150k), Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstrasse 12, 70599 Stuttgart, Germany; (E.H.B.P.);; Hiller, Eric; Department of Bioprocess Engineering (150k), Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstrasse 12, 70599 Stuttgart, Germany; (E.H.B.P.);; Marchetti, Filippo; Department of Life Sciences and Biotechnology, University of Ferrara, 44121 Ferrara, Italy, (S.V.);; Costa, Stefania; Department of Life Sciences and Biotechnology, University of Ferrara, 44121 Ferrara, Italy, (S.V.);; Pfannstiel, Jens; Core Facility Hohenheim, Mass Spectrometry Unit, University of Hohenheim, Ottlie-Zeller-Weg 2, 70599 Stuttgart, Germany; Konnerth, Philipp; Department of Conversion Technology of Biobased Resources, University of Hohenheim, Garbenstrasse 9, 70599 Stuttgart, Germany;; Vertuani, Silvia; Department of Life Sciences and Biotechnology, University of Ferrara, 44121 Ferrara, Italy, (S.V.);; Manfredini, Stefano; Department of Life Sciences and Biotechnology, University of Ferrara, 44121 Ferrara, Italy, (S.V.);; Hausmann, Rudolf; Department of Bioprocess Engineering (150k), Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstrasse 12, 70599 Stuttgart, Germany; (E.H.B.P.);; Gudiña, EduardoIn a scenario of increasing alarm about food waste due to rapid urbanization, population growth and lifestyle changes, this study aims to explore the valorization of waste from the retail sector as potential substrates for the biotechnological production of biosurfactants. With a perspective of increasingly contributing to the realization of the circular bioeconomy, a vegetable juice, derived from unsold fruits and vegetables, as a carbon source was used to produce lipopeptides such as surfactin and fengycin. The results from the shake flask cultivations revealed that different concentrations of vegetable juice could effectively serve as carbon sources and that the fed-batch bioreactor cultivation strategy allowed the yields of lipopeptides to be significantly increased. In particular, the product/substrate yield of 0.09 g/g for surfactin and 0.85 mg/g for fengycin was obtained with maximum concentrations of 2.77 g/L and 27.53 mg/L after 16 h, respectively. To conclude, this study provides the successful fed-batch cultivation of B. subtilis using waste product as the carbon source to produce secondary metabolites. Therefore, the consumption of agricultural product wastes might be a promising source for producing valuable metabolites which have promising application potential to be used in several fields of biological controls of fungal diseases.Publication Editorial: Microbial biosurfactants: updates on their biosynthesis, production and applications(2024) Hausmann, Rudolf; Déziel, Eric; Soberón-Chávez, GloriaPublication Bioprocess exploitation of microaerobic auto-induction using the example of rhamnolipid biosynthesis in Pseudomonas putida KT2440(2025) Grether, Jakob; Dittmann, Holger; Willems, Leon; Schmiegelt, Tabea; Benatto Perino, Elvio Henrique; Hubel, Philipp; Lilge, Lars; Hausmann, Rudolf; Grether, Jakob; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, Germany; Dittmann, Holger; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, Germany; Willems, Leon; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, Germany; Schmiegelt, Tabea; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, Germany; Benatto Perino, Elvio Henrique; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, Germany; Hubel, Philipp; Core Facility Hohenheim, Mass Spectrometry Core Facility, University of Hohenheim, Ottilie-Zeller-Weg 2, 70599, Stuttgart, Germany; Lilge, Lars; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, Germany; Hausmann, Rudolf; Department of Bioprocess Engineering, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, 70599, Stuttgart, GermanyBackground: In biomanufacturing of surface-active agents, such as rhamnolipids, excessive foaming is a significant obstacle for the development of high-performing bioprocesses. The exploitation of the inherent tolerance of Pseudomonas putida KT2440, an obligate aerobic bacterium, to microaerobic conditions has received little attention so far. Here low-oxygen inducible promoters were characterized in biosensor strains and exploited for process control under reduction of foam formation by low aeration and stirring rates during biosynthesis of rhamnolipids. Results: In this study, homologous promoters of P. putida inducible under oxygen limitation were identified by non-targeted proteomic analyses and characterized by fluorometric methods. Proteomics indicated a remodeling of the respiratory chain and the regulation of stress-related proteins under oxygen limitation. Of the three promoters tested in fluorescent biosensor assays, the promoter of the oxygen-sensitive cbb3-type cytochrome c oxidase gene showed high oxygen-dependent controllability. It was used to control the gene expression of a heterologous di-rhamnolipid synthesis operon in an auto-inducing microaerobic two-phase bioprocess. By limiting the oxygen supply via low aeration and stirring rates, the bioprocess was clearly divided into a growth and a production phase, and sources of foam formation were reduced. Accordingly, rhamnolipid synthesis did not have to be controlled externally, as the oxygen-sensitive promoter was autonomously activated as soon as the oxygen level reached microaerobic conditions. A critical threshold of about 20% oxygen saturation was determined. Conclusions: Utilizing the inherent tolerance of P. putida to microaerobic conditions in combination with the application of homologous, low-oxygen inducible promoters is a novel and efficient strategy to control bioprocesses. Fermentation under microaerobic conditions enabled the induction of rhamnolipid production by low oxygen levels, while foam formation was limited by low aeration and stirring rates.Publication Oral processing of anisotropic food structures: A modelling approach to dynamic mastication data(2024) Oppen, Dominic; Weiss, JochenMaterials that have been generated through a directionally oriented growth process often exhibit anisotropic properties. Plant materials such as tubers and roots or animal matter used to produce products such as steaks or pasta filata are characterized by an alignment of molecules, aggregates or cells in certain dimensions leading to differing properties depending on direction. Such an anisotropic property behavior is important for a wide range of quality attributes such as texture, appearance, stability and even aroma and taste. Especially the former is of critical importance to consumer liking and acceptance of foods. Structure-texture relationships have already been established for certain foods. For anisotropic foods though, a determination of such relationships is difficult, since the comminution of foods during chewing causes complex changes to the underlying anisotropic structure elements that are not easily measurable using conventional mechanical texture analysis tests such as cutting, shearing or compression. On the other hand, sensory tests using panels are very time consuming and often do not reveal structural causes for texture like or dislike by consumers. The lack of availability of suitable analytical techniques that allow for a description of texture properties relevant to mastication hampers especially the development of meat substitutes that are currently trending. The aim of this work was therefore to characterize changes to anisotropic structures induced by chewing (henceforth referred to as "oral processing") using a novel measurement approach that records kinematic and electromyographic properties of the chewing process. The kinematics of jaw movement were recorded using a 3D motion tracking system. Muscle activity was recorded using an electromyograph. From the measured data, characteristics for individual chews were calculated, which were represented in a linear mixed model as a function of the food structure. Section I provides the scientific basis for this work through a preface and a literature review. Grown and manufactured anisotropic foods are identified and described. A general overview of the production, phase phenomena and characterization methods for anisotropic food materials is given. Section II contains the oral processing experiments. In Chapter III, the focus was put on the impact of fiber length of grown structures on mastication behavior. Meat model systems with different microstructures but the same composition were produced. The model systems with anisotropic and isotropic microstructures were comminuted to different sizes, and the fiber length was inferred from the length of the particles, taking into account the particle size effect of chewing. The results indicate that longer fibers cause greater jaw movement and muscle activity. For instance, estimate peak muscle activity of anisotropic samples is 58.2857 µV higher (p=0.0156) compared to isotropic samples. Chapter IV describes minced meat products in which certain phase volumes were replaced by a finely comminuted meat mass. The aim of the study was to find detection limits beyond which an increase or decrease in muscle fiber cells does not lead to a further adjustment of the mastication properties. In the study, a transition point was identified at around 50 % of batter-like substances. Food models with more than 50 % of batter-like substance showed a smaller change in mastication parameters. The effect was more pronounced with higher proportions of fibrous material. Chapter V dealt with the topic of meat substitutes. A simple model of meat substitutes was used to test whether the effects found in anisotropic animal-based products can also be found in plant-based products. Hydrocolloid gels with different phase volumes of wet textured plant protein were produced. Similar effects for the animal-based products were observed, although the correlation was not as strong. It was hypothesized that a large part of the effect was due to the weak binding ability of hydrocolloid gels. Thus, the anisotropic particles could not be held together with a low proportion of the outer hydrocolloid gel and required less muscle activity despite a higher content of structured phase. Section III assessed alternative data evaluation strategies to the linear mixed model. The aim of the study in Chapter VI was to anticipate the model products from Chapter III using a classification approach. Algorithms of three categories were trained with the data set of the chewing processes. Two approaches were used to evaluate whether the algorithms could either resolve each individual food model with variations in microstructure (anisotropy) and macrostructure (particle size) or in microstructure only. For both approaches, the algorithms performed significantly better compared to a random guessing. The best classification results were achieved by the boosted ensemble learner "XGBoost", which assigned 96.617 % of all bites to the corresponding food microstructure. Furthermore, it was demonstrated that standardized and normalized oral processing data are almost not subject-dependent. In addition, feature importance analysis confirmed that lateral jaw movement is a good indicator of the presence of anisotropic food material and, with a weight of 0.39205, is the most important feature for classifying samples according to their structure. In summary, this work was able to show that the dynamic characteristics of mastication change depending on anisotropic properties. In general, modeling of mastication characteristics has never been conducted before and represents a promising advance over mean-based evaluation. The machine learning approach is also new in the field of oral processing and proved to be promising. For future research, it is proposed to correlate the dynamic features with sensory texture data to obtain direct correlations between chewing characteristics and texture attributes.Publication Ingenious wheat starch/Lepidium perfoliatum seed mucilage hybrid composite films: Synthesis, incorporating nanostructured Dy₂Ce₂O₇ synthesized via an ultrasound-assisted approach and characterization(2025) Zinatloo-Ajabshir,Sahar; Yousefi, Alireza; Jekle, Mario; Sharifianjazi, FariborzIn this study, Dy₂Ce₂O₇ nanostructures were fabricated using an environmentally friendly, ultrasound-assisted method. These nanostructures were then incorporated into a blend of wheat starch (WS) and Lepidium perfoliatum seed mucilage (LPSM), along with sodium montmorillonite (Na-MMT) nanoparticles. The composite films were produced through a casting method, combining these components to enhance the films' structural and functional properties. FTIR results confirmed the chemical interactions between the NPs and the biopolymeric matrix of the nanocomposites. SEM surface morphology and XRD crystallography results indicated that up to a 1 % weight ratio, the dispersion of Dy₂Ce₂O₇ in the nanocomposite matrix was uniform, while at higher percentages, due to nanoparticle aggregation, crystallinity increased. Interestingly, the elongation of nanocomposites containing Dy₂Ce₂O₇ increased, while their tensile strength and elastic modulus decreased. More than 92 % of UV radiation in the 240–360 nm range was absorbed with the inclusion of 1 % wt. Dy₂Ce₂O₇, and the water vapor permeability (WVP) significantly decreased. Among the Dy₂Ce₂O₇-based nanocomposites, TGA results showed that the WS/LPSM/MMT/Dy1 % sample had the highest thermal stability. Overall, based on the results of this study, the WS/LPSM/MMT/Dy1 % sample was introduced as a composite film with suitable physicochemical and mechanical properties for food and pharmaceutical packaging.Publication Bioprocess strategies for efficient microbial conversion of acetate as alternative biotechnological carbon source derived from lignocellulose streams(2024) Kiefer, Dirk; Hausmann, RudolfIn near future, humanity will be faced with the global challenges from climate change, fossil fuel depletion to food shortage. Our current economic system will thus need to make a transition into a sustainable bioeconomy which uses key technologies like biotechnology for conversion of renewable feedstocks. The majority of all biotechnological carbon sources is generated from food plants. In context to the global population growth coming along with food insecurity, competing use of these food plants for human and animal nutrition creates a substrate dilemma for future biotechnology. Future biorefineries will thus need to realize a paradigm shift to carbon sources generated from non-competing or waste resources. As such, especially lignocellulosic biomass is regarded as the central feedstock for a bio-based industry. Among the different substrate streams obtained by lignocellulose refining strategies, the C2 carboxylic acid acetic acid (from now on referred to as acetate) is one of the most common occurring components. In contrast to its high economic role as building block in the chemical industry, acetate shows low relevance as biotechnological carbon source yet. This is mainly related to its inhibitory characteristic, the reason for why acetate has been used in food preservation for thousands of years. However, most industrial platform organisms are also capable to grow on acetate as sole carbon source. It also shows several attractive characteristics for bioprocessing which is why research studies on microbial acetate conversion have significantly increased in the past years. Together with the potential routes to generate non-fossil bio-acetate in large quantities from non-food competing resources like lignocellulose and biomass-derived/waste C1 gas streams, acetate might become a next-generation platform substrate for a future bio-industry. In order to make acetate-based bioprocesses competitive to those using conventional sugar-based carbon sources, adapted process strategies for efficient acetate conversion need to be established. The present thesis is aimed to address efficient bioprocess strategies for biotechnological conversion of lignocellulosic acetate into microbial biomass and growth-coupled products under fed-batch culture conditions. The experimental studies presented in this work were divided into two parts: In Part I, the potential of acetate as carbon source for high cell density cultivation of industrial platform bacterium Corynebacterium glutamicum was evaluated. Preliminary growth studies with different initial acetate concentrations revealed a high natural acetate tolerance for wild-type ATCC 13032 with growth at high acetate levels up to 60 g/L. In addition, it was shown that maximum growth rates (μmax) of 0.47 h-1 for acetate concentrations below 10 g/L are competitive to that on D-glucose as common carbon source. By implementation of an online feeding control which enables automated supply of pure acetic acid (HAc) via pH control, high cell density cultivation on lignocellulosic acetate was demonstrated for the first time in a 42 L stirred-tank bioreactor. Optimization of the molar carbon-to-nitrogen feeding ratio resulted in a highly efficient bioprocess yielding cell densities up to 80.2 g/L CDW after 28.9 h with biomass yields (YXIS) of 0.35 g/g and space-time yields (STY) of 66.6 g/L·d. Part II focused on the potential of acetate as carbon source for integrated protein production in C. glutamicum. Batch cultures of genome-reduced strains MB001/MB001(DE3) demonstrated that acetate clearly shows no inhibitory effect on protein production of eYFP as model protein using C. glutamicum as production host. Interestingly, comparative expression studies with C. glutamicum T7 expression system indicated an up to 83 % higher biomass-specific production on acetate compared to D-glucose as carbon source. By transferring the implemented pH-coupled online feeding control for high cell density cultivation of strain MB001(DE3) pMKEX2-eyfp in a 42 L stirred-tank bioreactor, this study showed efficient protein accumulation on lignocellulosic acetate yielding final protein titers of 2.7 g/L after 27 h with product yields (YPIX) of 40 mg/g and volumetric productivities (PV) of 0.10 g/L·h. In conclusion, the presented results demonstrate the high biotechnological potential of acetate as alternative carbon source. In contrast to most other studies before, it is shown that a suitable process strategy based on pH-coupled online feeding control allows efficient microbial acetate conversion under industry-relevant fed-batch culture conditions. This work provides exemplary proof-of-concept bioprocesses for high cell density cultivation on lignocellulosic acetate and its growth-coupled conversion into protein using industrial platform organism C. glutamicum. Therefore, the presented thesis contributes to the development of efficient concepts for microbial conversion of next-generation platform substrates like lignocellulosic acetate.Publication Characterization of aroma and sensorial variation of basil and ginger during short-time drying process(2024) Liang Jiaqi; Zhang, YanyanIndustries are increasingly interested in aromatic herbs and spices, such as basil and ginger, which play a crucial role in daily life as flavoring agents in foods, beverages, and pharmaceuticals. Basil, an annual herb from the mint family (Lamiaceae), is renowned for its wonderful “royal” fragrance and numerous health benefits. Ginger, one of the most widely consumed dietary spices worldwide, has seen a surge in interest due to its significant healthpromoting properties. In 2023, global market sales for basil leaves and ginger reached 50 million euros and 4.2 billion euros, respectively. As may other herbs and spices, basil and ginger are typically used in dried form to extend shelf life and facilitate transportation. However, the drying process significantly alter the aroma from fresh samples, reduce the quality of the final products and generate numerous by-products. This study aims to identify the off-odor compound(s) produced during basil drying process using molecular sensory techniques and to develop effective strategies to inhibit their formation. Additionally, ginger peel and ginger fiber by-products generated during the industrial and domestic use, as well as the spray drying process, were investigated and reintroduced into the procedure to preserve the aroma compounds of ginger and promote environmental sustainability. In the first part of the study, a method using stir bar sorptive extraction combined with gas chromatography-mass spectrometry-olfactory (SBSE-GC-MS-O) was established to analyse the aroma changes of basil and ginger during short-term spray drying. This approach was designed to maximize desorption efficiency for various odorants with diverse physicochemical properties under different desorption conditions through four types of mathematical modelling. Among these models, the Random Forest model demonstrated the highest performance and minimal errors, with an R value of 0.910 after validation using a dataset of six new compounds. In addition, the model determined that cryo-focusing temperature was the most important factor, followed by molecular weight, log P, boiling point, desorption temperature, desorption time, and helium flow. This algorithm can be further utilized to predict the optimal parameters for maximizing desorption efficiency in aroma analysis of basil and ginger by SBSE-GC-MS-O. Subsequently, to investigate the formation of the hay-like off-odor that lowers consumer acceptability in dried basil products, the responsible compound was identified in thawed, airdried, and spray-dried basil samples using a trained human panel (n = 10) and gas chromatography–mass spectrometry–olfactometry. 3-Methylnonane-2,4-dione (3-MND) was found to be the odorant contributing to the hay-like off-odor in all basil samples. In order to reduce this odorant, the effects of light, oxygen, and temperature on the formation of 3-MND during the processes of thawing, spray drying, and air drying were studied based on a potential pathway involving 3-MND precursors. The results revealed that controlling light exposure, employing nitrogen protective environment, and maintaining low temperatures are critical processing parameters for minimizing the generation of the hay-like compound 3-MND, thereby meeting consumer demands for high-quality dried basil products. Regarding the processing of ginger, the drying process generates a significant amount of ginger peel as an industrial by-product. To facilitate environmental sustainability and establish a reference for its potential applications, the effect of ginger peel on aroma, sensory profiles, and nutrition-related physicochemical properties was investigated. The total concentration of aroma compounds in unpeeled ginger was 1.3 times higher than that in peeled ginger, according to SBSE-GC-MS-O analysis. Sensory evaluation data indicated that unpeeled ginger had significantly enhanced citrus-like and fresh impressions compared to peeled ginger, which is associated with the higher odor activity values of odorants such as β-myrcene (pungent, citruslike), geranial (citrus-like), citronellal (citrus-like, sourish), and linalool (floral, fresh). Additionally, the total polyphenol content in unpeeled ginger was 7.96 mg/100 g higher than that in peeled ginger. Unpeeled ginger not only demonstrates more intense aromatic and sensory qualities but also offers superior nutritional and environmental benefits, making it a promising option for future global spice use and reducing ginger side streams. In the spray drying process of ginger, ginger fibre is also typically regarded as industrial byproduct, as ginger juice is often used as a feed material. To achieve sustainable development and produce a clean-labeled product, a split-stream spray-drying process was developed to address sugar-rich feed solutions by reintroducing ginger fiber in their natural composition as a carrier material, rather than treating them as a by-product. The characterizations of both feed materials were then compared. The method was optimized for aroma retention by adjusting the inlet and outlet temperatures to 220 ℃ and 80 ℃, respectively. Aroma decoding results using SBSE-GC-MS-O demonstrated that reintegrating ginger fiber significantly increased the concentration of eight key odorants, including hexanal, linalool, neral, borneol, geranial, citronellol, nonanoic acid, and α-bisabolol, in comparison to the concentration observed in ginger juice. This presents a promising solution for maximizing the utilization of ginger in spray drying, enhancing the aroma profiles of feed material, and addressing sustainability considerations in the food industry. Overall, the presented work comprehensively explores the challenges and potential solutions associated with the drying process of basil and ginger, highlighting the impact of various processing conditions on aroma and sensory properties. By identifying key off-odor compounds and optimizing techniques to reduce their formation, as well as investigating aroma profiles and sustainable approaches for utilizing by-products such as ginger peel and ginger fiber, this research offers valuable insights into improving both the aromatic quality and environmental sustainability of dried herb and spice products.Publication The influence of growth rate-controlling feeding strategy on the surfactin production in Bacillus subtilis bioreactor processes(2024) Hiller, Eric; Off, Manuel; Hermann, Alexander; Vahidinasab, Maliheh; Benatto Perino, Elvio Henrique; Lilge, Lars; Hausmann, RudolfBackground The production of surfactin, an extracellular accumulating lipopeptide produced by various Bacillus species, is a well-known representative of microbial biosurfactant. However, only limited information is available on the correlation between the growth rate of the production strain, such as B. subtilis BMV9, and surfactin production. To understand the correlation between biomass formation over time and surfactin production, the availability of glucose as carbon source was considered as main point. In fed-batch bioreactor processes, the B. subtilis BMV9 was used, a strain well-suited for high cell density fermentation. By adjusting the exponential feeding rates, the growth rate of the surfactin-producing strain, was controlled. Results Using different growth rates in the range of 0.075 and 0.4 h-1, highest surfactin titres of 36 g/L were reached at 0.25 h-1 with production yields YP/S of 0.21 g/g and YP/X of 0.7 g/g, while growth rates lower than 0.2 h-1 resulted in insufficient and slowed biomass formation as well as surfactin production (YP/S of 0.11 g/g and YP/X of 0.47 g/g for 0.075 h-1). In contrast, feeding rates higher than 0.25 h-1 led to a stimulation of overflow metabolism, resulting in increased acetate formation of up to 3 g/L and an accumulation of glucose due to insufficient conversion, leading to production yields YP/S of 0.15 g/g and YP/X of 0.46 g/g for 0.4 h-1. Conclusions Overall, the parameter of adjusting exponential feeding rates have an important impact on the B. subtilis productivity in terms of surfactin production in fed-batch bioreactor processes. A growth rate of 0.25 h-1 allowed the highest surfactin production yield, while the total conversion of substrate to biomass remained constant at the different growth rates.Publication Development of rapid analytical methods for coffee quality assessment: Spectroscopy and chemometrics approach(2024) Munyendo, Leah Masakhwe; Hitzmann, Bernd; Zhang, YanyanThe assessment of coffee quality is based on the physical characteristics (bean quality), chemical constituents, and cup quality. Different factors, including altitude, genetics, management conditions, presence of adulterants, roasting, geographical origin, processing methods, and storage, affect the coffee quality. To meet the consumers' expectations regarding quality, the development of fast, new, and advanced analytical techniques for assessing the factors affecting coffee quality is a central aspect. Therefore, this research aimed to develop spectroscopic techniques complemented with chemometrics for evaluating the factors affecting coffee quality. The first specific objective was to investigate the ability of a deep autoencoder neural network to detect adulterants in roasted Arabica coffee and to determine a coffee’s geographical origin using near‐infrared (NIR) spectroscopy. Arabica coffee was adulterated with Robusta coffee or chicory at adulteration levels ranging from 2.5 % to 30 % in increments of 2.5 % at light, medium, and dark roast levels. Based on the results, all the samples adulterated with chicory were detectable by the autoencoder at all roast levels. For Robusta-adulterated samples, the detection was possible at adulteration levels above 7.5 % at medium and dark roasts. One can attribute the observations to potential differences in the chemical composition among the samples. Additionally, it was possible to differentiate coffee samples from different geographical origins. As a continuation of the first objective, the potential of NIR spectroscopy to quantify Robusta coffee or chicory in roasted Arabica coffee using different regression models constructed from the linear discriminant analysis (LDA) or principal component analysis (PCA) features was investigated. In addition, two classification methods (k-nearest neighbor regression (KNR) and LDA) were used. The regression models derived from LDA-extracted features exhibited better accuracies than those derived from PCA-extracted features. The two feature extraction methods exhibit differences in their working principle. PCA focuses on identifying the direction of maximum variance regardless of the adulteration levels. In contrast, LDA identifies the feature subspace that optimizes the separability of the classes (adulteration levels) and minimizes the variance within the class. Therefore, LDA extracted the features better than PCA, explaining the better performance of the regression models constructed from its features. The models provided satisfactory results with the coefficient of determination (R2) values above 0.92 for both the adulterants, indicating their efficiency in quantifying Robusta coffee or chicory in roasted Arabica coffee. For the classification methods, the LDA model performed better than KNR. Another focus of this doctoral research was to develop analytical tools based on Raman and NIR spectroscopy for real-time monitoring of 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 5, 7, 9, 11, 13, 15, 17, 19, 21, 23, 25, 27, and 29 minutes. Four process runs were performed for each coffee species. The spectra of the ground samples were taken using the two spectrometers and modeled by the KNR, partial least squares regression (PLSR), and multiple linear regression (MLR). All the models based on the NIR spectra 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 < 9.469 %) and high R2 (> 0.916) values. Similarly, all the models based on the Raman spectra provided acceptable prediction accuracies for monitoring the dynamics of chlorogenic acid, trigonelline, and DPPH radical scavenging activity (pRMSEP < 7.849 % and R2> 0.944). In conclusion, this research proposes different approaches that would allow valuable decisions regarding coffee quality to be made quickly and efficiently. The study suggests using NIR spectroscopy to determine a coffee’s geographical origin and detect and quantify adulterants in roasted coffee. The findings reveal that the method could be a promising tool for routine coffee quality control applications in the coffee industry and other legal sectors. The study also proposes using different spectroscopic methods (NIR and Raman) to monitor a coffee roasting process. One can consider the presented approaches as essential steps toward optimizing the roasting process at an industrial scale as they permit instantaneously taking significant process decisions.Publication Bioprospecting for novel lipopeptide-producing strains for potential application in food and agriculture(2024) Akintayo, Stephen Olusanmi; Hausmann, RudolfThe need for sustainable alternatives to chemical products has been a huge topic in recent years and has put a demand on researchers and biotechnological companies to come up with bio-based alternatives to several chemical products. In line with this, interest in biosurfactants as alternatives to chemical surfactants is on the rise. Biosurfactants produced by microorganisms have great potential for application in detergents, personal care products, and pharmaceuticals, as well as in environmental, food processing, and agricultural applications. There are a few types of biosurfactants, including lipopeptides, which are primarily produced by Bacillus species and exhibit antimicrobial properties in addition to the well-known surface activity, surface tension reduction, and emulsifying ability of biosurfactants. Like other biosurfactants, lipopeptides have found more use in environmental applications such as bioremediation and microbial enhanced oil recovery (MEOR), while their use in agriculture and food industries remains limited due to concerns that may be related to acceptability, compatibility, and low yield by wild-type strains. To overcome these challenges, this thesis sought to find novel wild-type lipopeptide-producing strains from food-related sources that could be presumably safe for use in agriculture and food applications. To achieve this goal, a screening approach that combined several methods was adopted to identify potential high-yield wild-type, and possibly novel lipopeptide-producing strains. The ability of selected strains as promising biocontrol agents in agriculture was also evaluated. In Publication 1, potential lipopeptide-producing strains were isolated from food-related sources and screened for lipopeptide production. The screening approach combined microbiological and molecular identification of strains, with screening methods based on biosurfactant properties, as well as chemical analysis of surfactin production. Strains with promising lipopeptide-production potential belonging to three genera of Bacillus, Lysinibacillus and Priestia were identified. These strains included several exotic species that were either previously unknown or minimally studied with respect to LP production. Multiple strains that produced more than 150 mg L-1 surfactin, including a B. subtilis strain with a yield of about 1.5 g L−1 were discovered. In Publication 2, two promising LP-producing B. velezensis strains ES1-02 and EFSO2-04 were evaluated for their biocontrol potential and compared with commercial biocontrol strains B. velezensis QST713 and FZB42. The isolated strains demonstrated biocontrol ability comparable to QST713 against Diaporthe spp., which are notorious fungal pathogens of soybeans and other economically important crops. Co-incubation of strain ES1-02 with the phytopathogen D. longicolla induced a 10-fold increase in surfactin production. The broader molecular response of B. velezensis to plant pathogens investigated through an associated global proteome analysis showed the adaptation and response mechanisms of B. velezensis to plant pathogens. In general, B. velezensis seemed to adopt LP- modulation, physiological adaptation, and increased abundance of antimicrobial compounds as antagonistic and adaptation strategies for interaction with the phytopathogen D. longicolla. In Publication 3, genomic techniques were used in the discovery and description of a novel lipopeptides-producing species of the genus Lysinibacillus for which the name Lysinibacillus irui sp. nov. was proposed. This Gram-positive, motile, aerobic, rod-shaped, endospore-forming strain designated IRB4-01T was isolated from fermented African locust beans (Iru) and as such was named after Iru. A comprehensive chemotaxonomic analysis of the strain showed that the cell wall peptidoglycan type is A4α (Lys–Asp), and MK-7 is the major respiratory quinone. Detailed information about the polar lipids and major cellular fatty acids was also obtained. The G+C content of the genomic DNA was 37.4 mol%. Surfactin production by this novel strain was described in Publication 1 of this work.Publication Food informatics - Review of the current state-of-the-art, revised definition, and classification into the research landscape(2021) Krupitzer, Christian; Stein, AnthonyBackground: The increasing population of humans, changing food consumption behavior, as well as the recent developments in the awareness for food sustainability, lead to new challenges for the production of food. Advances in the Internet of Things (IoT) and Artificial Intelligence (AI) technology, including Machine Learning and data analytics, might help to account for these challenges. Scope and Approach: Several research perspectives, among them Precision Agriculture, Industrial IoT, Internet of Food, or Smart Health, already provide new opportunities through digitalization. In this paper, we review the current state-of-the-art of the mentioned concepts. An additional concept is Food Informatics, which so far is mostly recognized as a mainly data-driven approach to support the production of food. In this review paper, we propose and discuss a new perspective for the concept of Food Informatics as a supportive discipline that subsumes the incorporation of information technology, mainly IoT and AI, in order to support the variety of aspects tangent to the food production process and delineate it from other, existing research streams in the domain. Key Findings and Conclusions: Many different concepts related to the digitalization in food science overlap. Further, Food Informatics is vaguely defined. In this paper, we provide a clear definition of Food Informatics and delineate it from related concepts. We corroborate our new perspective on Food Informatics by presenting several case studies about how it can support the food production as well as the intermediate steps until its consumption, and further describe its integration with related concepts.