Newest publications
Metabolic rewiring compensates for the loss of amino acid biosynthesis in Bacillus subtilis
(2024) Yousef Mardoukhi, Mohammad Saba; Commichau, Fabian M.
Amino acids are considered as some of the earliest organic molecules to form on Earth. Serving as the building blocks of proteins, they are intricately connected to nearly every life process. Therefore, amino acid metabolism needs to be precisely regulated in any living organism. Amino acid metabolism includes the biochemical pathways responsible for the synthesis, degradation, and utilization of amino acids. Most of the bacteria, particularly the Gram-positive model bacterium Bacillus subtilis, have the capability to synthesize all proteinogenic amino acids or, if available, import them from the environment. Throughout evolution, different metabolic pathways have emerged to maintain metabolites level inside the cells. Some biosynthetic pathways are unknown as they are not primary routes or are typically inactive under normal conditions. However, they may become active under specific circumstances. Two very important pathways, previously not known to be substituted by alternative routes, involve de novo biosynthesis of glutamate, which is an essential amino group donor in every cell. Many bacteria can synthesize glutamate using a NADPH + H+-dependent glutamate dehydrogenase (GDH). Alternatively, glutamate can be produced by the combined action of the ATP-dependent glutamine synthetase (GS) and the NADPH + H+-dependent glutamate synthase (GOGAT). B. subtilis only employs the GS-GOGAT pathway for de novo synthesis of glutamate. In the context of this work, it was shown that a B. subtilis deficient for the GS-GOGAT pathway may employ the aspartase AnsB and aspartate transaminase AspB for the synthesis of glutamate in biologically significant amounts. Genetic analyses revealed that the aspartase AnsB converts ammonium and the tricarboxylic acid cycle intermediate fumarate to aspartate. Subsequently, the aspartate transaminase AspB transfers the amino group from aspartate to α-ketoglutarate, resulting in the production of L-glutamate and oxaloacetate. This observation challenges the well-established point of view of whether the GS-GOGAT-dependent pathway is indeed the only route for de novo synthesis of glutamate in nature. It was also set out to explore which amino acids could serve as the sole sources of carbon and nitrogen in the background of a B. subtilis strain that is a genetically stable glutamate auxotroph. The aim was to understand the conversion of the amino acids into glutamate and further to α-ketoglutarate, a reaction that is facilitated by the enzymatic activity of the GDHs RocG/GudB. It turned out that some of the amino acids are toxic for B. subtilis. However, B. subtilis can quickly develop resistance by the acquisition of mutations that result in reduced and enhanced amino acid uptake and export, respectively. Moreover, the toxicity of some amino acids may be reduced by increased degradation of glutamate. Furthermore, with focus on the toxicity of asparagine, it could be demonstrated that AimA, which has been characterized as a general amino acid importer, serves as a low affinity asparagine transporter in B. subtilis. Finally, AzlCD, which was previously described as an exporter for histidine and branched-chain amino acids, also exports asparagine. Thus, B. subtilis can adapt to amino acid toxicity in various ways.
On capital and habitus: social class and its role in entrepreneurship
(2024) Rönnert, Anna-Lena; Kuckertz, Andreas
Entrepreneurship is often heralded as a pathway to upward mobility, epitomizing the ideal of the "rags to riches" narrative. However, recent research on marginalized entrepreneurs suggests that social class may play a significant role in shaping entrepreneurial outcomes, challenging the notion that entrepreneurship offers equal opportunities to all. Although research explicitly linking entrepreneurship with social class theories remains limited, social class appears to influence access to various forms of capital and shape the habitus that guides entrepreneurial behavior. Consequently, understanding these dynamics is essential to addressing inequalities in entrepreneurship. This dissertation explores how social class affects an individual’s entrepreneurial journey, with three studies included in this dissertation approaching the topic from different conceptual perspectives.
Study 1 provides an integrative review of the literature on social class origin and entrepreneurship by seeking to understand: What is an entrepreneur’s social class origin? How does social class origin influence entrepreneurial outcomes and social class destinations? How should future entrepreneurship research address social class origin? In response, the study proposes a theoretical framework that outlines how entrepreneurs’ social class origin impacts entrepreneurial outcomes through entrepreneurial resources at hand, entrepreneurial habitus formation, and access to external resources and opportunities, and how these themes facilitate upward mobility, downward mobility, or class maintenance. In addition, this review establishes the foundations for future empirical research by developing a comprehensive future research agenda on social class in entrepreneurship.
While Study 1 sets the broader theoretical context, Study 2 turns to the lived experiences of upwardly mobile entrepreneurs. Drawing on Lahire’s reconceptualization of habitus, this study seeks to explore how the internalized dispositions formed through social class origin and upward social mobility interact with the socio-cultural context of entrepreneurship and shape entrepreneurial behavior. Through life history interviews with 36 entrepreneurs, the study identifies seven entrepreneurial archetypes that reflect varying degrees of (mis)alignment tied to classed socio-cultural contexts and internal-ized dispositions and display distinct entrepreneurial behaviors in response. These findings highlight the socio-cultural barriers faced by upwardly mobile entrepreneurs, which persist despite the accumulation of capital through social mobility, and raise questions about the inclusivity of entrepreneurship as a viable pathway across different social hierarchies.
In contrast to the focus on individual experiences of upward social mobility in Study 2, Study 3 examines the effects of educational attainment as a social class signal and the intersection with gender and migration backgrounds on the likelihood of obtaining different types of external financial capital. Analyzing 63,023 venture-year observations from Germany, this study shows that entrepreneurs without academic qualifications are less likely to secure equity capital but more likely to obtain debt financing. Additionally, the study underscores how intersectional factors, such as gender and migration background, interact with social class to influence financial capital acquisition. These results reveal the complex ways in which social class signals shape entrepreneurial access to resources, offering a broader perspective on structural inequalities in entrepreneurship.
Overall, this dissertation provides a comprehensive examination of the role of social class in entrepreneurship, highlighting the intricate connections between class-based capital and habitus. By combining the broad theoretical perspectives of Study 1 with the personal life histories in Study 2 and the large-scale quantitative analysis in Study 3, this work offers a multidimensional understanding of how social class affects an individual’s entrepreneurial journey. The findings contribute to the emerging field of research on social class and entrepreneurship by shedding light on the structural barriers faced by entrepreneurs from different social backgrounds, as well as the unique strengths they bring to the entrepreneurial process. While this thesis makes significant strides in advancing our understanding of the interplay between social class and entrepreneurship, there remains much to uncover. Consequently, it lays the groundwork for future research by outlining a comprehensive agenda that addresses the complex dynamics of social class along the Bourdieusian concepts of capital and habitus, ultimately aiming to promote a more inclusive understanding of entrepreneurship.
Almond-like aroma formation of acid whey by Ischnoderma benzoinum fermentation: potential application in novel beverage development
(2025) Hannemann, Lea; Klauss, Raphaela; Gleissle, Anne; Heinrich, Patrick; Braunbeck, Thomas; Zhang, Yanyan; Hannemann, Lea; Department of Flavor Chemistry, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, Stuttgart, Germany; Klauss, Raphaela; Department of Soft Matter Science and Dairy Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstr. 21, Stuttgart, Germany; Gleissle, Anne; Department of Soft Matter Science and Dairy Technology, Institute of Food Science and Biotechnology, University of Hohenheim, Garbenstr. 21, Stuttgart, Germany; Heinrich, Patrick; Aquatic Ecology and Toxicology Group, Center for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, Heidelberg, Germany; Braunbeck, Thomas; Aquatic Ecology and Toxicology Group, Center for Organismal Studies, University of Heidelberg, Im Neuenheimer Feld 504, Heidelberg, Germany; Zhang, Yanyan; Department of Flavor Chemistry, Institute of Food Science and Biotechnology, University of Hohenheim, Fruwirthstr. 12, Stuttgart, Germany
To address the sourish off-aroma of acid whey and enhance its upcycling, a new basidiomycete Ischnoderma benzoinum -mediated fermentation system was developed using pure acid whey as the sole substrate. A pleasant sweetish and marzipan-like odor was perceived after fermentation within 7 d at 24 °C in darkness, which was shaped from key contributors including 4-methoxybenzaldehyde (odor activity value (OAV) 878), 3-methylbutanal (OAV 511), 3,4-dimethoxybenzaldehyde (OAV 50), and benzaldehyde (OAV 28). The typical sweetish and almond-like odor persisted well after ultrahigh-temperature processing, though its intensity decreased slightly. Concurrently, the fermentation reduced lactose from 52 to 20 g/L but increased the contents of essential amino acids like threonine, leucine, and lysine. No significant cytotoxicity or genotoxicity differences were found between fermented and unfermented whey. Overall, the study highlights the capability of I. benzoinum fermentation to enhance the flavor of acid whey, offering a promising approach for creating nutritional and flavorful acid-whey-based products.
Four new families of Arbuscular mycorrhizal fungi within the order glomerales
(2024) da Silva, Gladstone Alves; de Assis, Daniele Magna Azevedo; Sieverding, Ewald; Oehl, Fritz; da Silva, Gladstone Alves; Departamento de Micologia, Universidade Federal de Pernambuco, Cidade Universitária, Av. da Engenharia s/n, Recife 50740-600, PE, Brazil; de Assis, Daniele Magna Azevedo; Departamento de Micologia, Universidade Federal de Pernambuco, Cidade Universitária, Av. da Engenharia s/n, Recife 50740-600, PE, Brazil; Sieverding, Ewald; Institute of Agricultural Sciences in the Tropics (Hans-Ruthenberg Institute), University of Hohenheim, Garbenstr. 13, D-70599 Stuttgart-Hohenheim, Germany; Oehl, Fritz; Competence Division for Plants and Plant Products, Agroscope, Müller-Thurgau-Strasse 29, CH-8820 Wädenswil, Switzerland; Sipiczki, Matthias
Based on molecular phylogenetic analyses, and also considering morphological characters, four new families are separated from the family Glomeraceae within the order Glomerales and the class Glomeromycetes. The revised family Glomeraceae comprises only four genera: the type genus Glomus , Complexispora , Sclerocarpum and Simiglomus . Septoglomeraceae fam. nov. comprises, besides Septoglomus , Funneliformis , Funneliglomus , Blaszkowskia and Viscospora . Sclerocystaceae fam. nov. is represented by the type genus Sclerocystis but also by Halonatospora , Oehlia , Parvocarpum , Rhizoglomus and Silvaspora . Kamienskiaceae fam. nov. encompasses Kamienskia , Microkamienskia and Epigeocarpum . Finally, Dominikiaceae fam. nov. includes the genera Dominikia , Macrodominikia gen. nov., Microdominikia , Nanoglomus and Orientoglomus . The genera Oehlia and Halonatospora form two other clades well separated from Silvaspora , Sclerocystis and Rhizoglomus and might represent two further families within Glomerales. This deeper separation is, in our opinion, fully supported by molecular phylogeny, but in view of the low numbers of taxa, the separation is not yet proposed at this stage of research progress.
Retail investor behavior and financial retail products: evidence from the 2nd European Retail Investment Conference
(2014) Burghof, Hans-Peter; Koch, Carolin; Meyer, Stephan; Schroff, Sebastian; Burghof, Hans-Peter; Prof. Dr. Hans-Peter Burghof, University of Hohenheim, Department of Banking and Finance, 70599 Stuttgart.; Koch, Carolin; Carolin Koch, University of Hohenheim, Department of Banking and Finance, 70599 Stuttgart.; Meyer, Stephan; Stephan Meyer, Karlsruhe Institute of Technology, Research Group Financial Market Innovation, 76131 Karlsruhe.; Schroff, Sebastian; Sebastian Schroff, University of Hohenheim, Department of Banking and Finance, 70599 Stuttgart.