Wecome to hohPublica, the platform for online publications of the University of Hohenheim!

hohPublica offers worldwide free access to scientific publications of the University of Hohenheim in the sense of Open Access.

As a member of the university, you can easily publish your publications online here. We ensure the long-term availability of the archived documents as well as the visibility through indexing in search engines and relevant library reference systems!


Newest publications

Uptake of pathogenic Escherichia coli into crop plants
(2023) Detert, Katharina Margarete; Schmidt, Herbert
Contaminations of fresh produce by enterohemorrhagic Escherichia coli (EHEC) have been an increasing source of human disease outbreaks in the past few decades. In particular, the large disease outbreak in 2011 in Germany has left many questions about the survival of EHEC in soil and the colonization of plants unanswered. Agricultural soil as a reservoir for EHEC strains represents an important contamination source for crop plants. The use of cattle manure for soil fertilization or contaminated irrigation water can result in the introduction of pathogens in fields. To prevent the transfer of pathogens into the food chain, the German fertilizer ordinance disallows the use of organic fertilizer 12 weeks before harvesting the crop plants. However, it is expected that EHEC survives for longer and therefore continue to pose a risk for crop plant contamination. In this study, the overall survival ability of the pathogenic E. coli O104:H4 strain C227/11Φcu, which represents a stx2a-negative derivative of the 2011 outbreak strain C227/11, in agricultural soil was investigated. Thereby, different environmental conditions, soil types and genetic factors of the bacterial strain were identified as influencing factors. Furthermore, the ability of E. coli O104:H4 strain C227/11Φcu to colonize lamb’s lettuce via the root system was investigated to demonstrate that contamination of soil can result in crop plant contamination. In the first publication, the survival of E. coli O104:H4 strain C227/11Φcu in soil microenvironments containing either diluvial sand or alluvial loam was investigated. Two different temperatures (4°C and 22°C) were used and the samples were incubated for more than 12 weeks. The study aimed to analyze whether cattle manure addition prolongs EHEC survival in the soil microenvironments. In the last step, the survival studies were performed using ΔrpoS and ΔfliC deletion mutant strains of C227/11Φcu. The results demonstrated that E. coli O104:H4 strain C227/11Φcu survived for at least 12 weeks in the soil microenvironment model. The survival rate was influenced by the soil type and the temperature. In more detail, the incubation at lower temperature prolonged the survival rate and pathogens were detected up to 20 weeks after inoculation. The application of contaminated cattle manure increased the survival ability at 22°C. Sigma factor RpoS was recognized as an important factor for soil survival. The rpoS deletion mutants showed significant reduction of the survival period while FliC did not influence the overall survival ability in these experiments. To investigate the influence of further genetic factors of the bacterial strain in more detail and thereby characterize all transcription activities, transcriptome analysis was performed in the second publication. Since the strain showed the best survival in alluvial loam at 4°C, this condition was used for the next experiments. To decrease the amount of competing soil microbiota, the soil samples were autoclaved prior inoculation. After inoculation and after 1 and 4 weeks, samples were taken for RNA isolation. The differential expression analysis was performed using the sample from time point 0 as control. The analysis revealed that stress response genes and genes of the primary metabolism were upregulated after 1 and 4 weeks. In addition, genes and gene sets for the uptake of various carbohydrates or amino acids were upregulated, indicating adaption to an environment with low nutrient availability. Moreover, the results of the second publication demonstrated that persistence of C227/11Φcu in soil is related with a complex interface of metabolic networks. The third paper focused on the colonization of lamb’s lettuce by E. coli O104:H4 strain C227/11Φcu via the root system. Surface-sterilized seeds were cultivated on Murashige-Skoog agar or in autoclaved agricultural soil and migration into the edible portions of the plants was analyzed after 2, 4 and 8 weeks. The results of this publication demonstrated that migration into the edible parts occurred when the surrounding agar or soil was contaminated. This highlighted the threat of plant contamination with pathogenic E. coli on the field as a result of soil contamination.
Assessing social aspects of biobased value chains
(2024) Marting Vidaurre, Nirvana Angela; Lewandowski, Iris
Achieving human well-being for all humanity, reducing inequality, and eradicating poverty while preserving the environment are the aims of sustainable development. The bioeconomy offers alternative ways of utilising biomass and other biogenic resources with the objective of addressing global challenges relevant for sustainable development such as resource scarcity, climate change and food security. Lignocellulosic perennial crops like miscanthus, have been investigated as a sustainable source for energy and materials. While various studies assessing the environmental performance of lignocellulosic crops have been published, the analysis of the social dimension of such systems has been little explored. Existing frameworks to perform social assessments are general in their coverage of social aspects and provide long lists of social impact categories, for which adaptation and prioritization is needed according to the specific case being analysed. Furthermore, existing methodologies for social life cycle assessment (S-LCA) leave the practitioner to choose between pursuing a context-specific analysis or a general (country or sector specific) analysis considering the value chain. To date there is no methodology to perform a S-LCA in an integrated manner for both the foreground and background systems of a biobased value chain, which takes into account the different requirements for analysing these systems. The foreground system is composed by the core processes being analysed, while the background system is constituted by the processes needed to supply inputs required for the foreground system. This doctoral thesis aims to develop an integrated methodology to assess the foreground and the background systems of biobased value chains, which combines techniques for performing a context-specific assessment of the foreground system and a generic assessment of the background system. The overall question that this study aims to answer is how to proceed in assessing the social aspects of a biobased value chain covering both the foreground and the background systems of a production process considering the study is an ex-ante analysis? The specific objectives to answer this question are i) to identify which social aspects are relevant for the assessment of biobased value chains, ii) to identify which aspects are to be considered when assessing the potential social impacts of agricultural production processes on the stakeholder “farmer” and iii) to develop a social risk assessment approach that is regionalized in order to assess the potential social impacts within biobased value chains. To achieve the first objective a literature review of empirical studies covering social impacts of agricultural and forestry value chains was performed. This helped in the identification of social aspects that are often assessed and reported. Then the Methodological Sheets for Subcategories in S-LCA were used as a reference to allocate the social aspects reported and evaluated by empirical literature and review studies to those impact subcategories proposed by the sheets. This enabled the identification of social aspects often assessed and those potentially overlooked in the sheets. To achieve the second objective a survey among farmers in a region of Croatia was conducted. Additionally, the study aimed to assess the feasibility of cultivating miscanthus in the region, taking into account potential challenges and opportunities, as well as farmers' willingness to adopt the crop miscanthus. The third objective of performing a regionalized social risk assessment of a biobased value chain was achieved by following the SOCA approach in combination with EXIOBASE 3 as a source of regional information on the origin of inputs and for the estimation of worker hours. This analysis used a case study based on the production of advanced biofuels in Croatia to assess the shortcomings of the methodology. The results showed that the Methodological Sheets for Subcategories in S-LCA provide good coverage of social topics relevant for biobased value chains, but that the stakeholders “smallholder” and “family farm” are not adequately addressed. Drawing on the empirical literature reviewed, the study emphasizes the relevance of these stakeholders in the analysis of biobased value chains, and proposes criteria for consideration in the assessment of these stakeholders. Furthermore, the interviews with farmers revealed that the aspects most valued by them were health and safety, access to water, land consolidation and rights, income and local employment, and food security. Responses to the question of whether they would adopt the crop miscanthus highlight the importance of an established market, good trading conditions and profitability of cultivation. The farmers regarded the provision of subsidies as one of the main factors that make a crop attractive. Opportunities for the adoption of the miscanthus cultivation are related to high yields and low input requirements. Barriers include land conflicts and land availability. Results also showed that mainly harvesting operations were identified as hotspots in the local agricultural operations due to the amount of worker hours required for these processes in comparison to the rest of the agricultural operations. The main contribution of this study is the development of an integrated approach that provides guidance for assessing comprehensively the foreground and background systems of biobased value chains. This consists of a local perspective and a value chain perspective of not yet established value chains. The methodology and framework developed serve for the early identification of potential social impacts in biobased value chains, specifically agricultural value chains. In the current literature, this methodology could be part of what is called materiality assessment. The theoretical framework developed serves for the analysis of the stakeholders “smallholder” and “family farm” and recommends the subsequent involvement of this stakeholder in the selection of context-relevant impact categories. The participation of these stakeholders is important to acquire local knowledge and to select impact categories that reflect their interests, merging a top-down with a bottom-up approach. The social risk assessment to analyse the background system should be applied when the value chain suppliers are not known and when a rapid assessment of the social risk of the value chain is required. The ultimate goal of S-LCA is to provide quality information about potential social impacts in production systems to decision makers, which will take action to reduce inequalities in the different regions of the world and thus contributing to achieve a more sustainable economy.
Formation and properties of inorganic Si-contaminant compounds
(2023) Stein, Mathias; Rennert, Thilo
Environmental contamination is the most pressing issue of our global society. Among others, contamination with potentially toxic elements (PTEs) such as cadmium (Cd), copper (Cu), and lead (Pb) threatens organisms, humans, and entire ecosystems. Silicon (Si) is known to benefit the resilience to such abiotic stresses and its application showed to alleviate PTE toxicity. These beneficial effects are predominantly attributed to in planta processes, but PTE immobilization in soil induced by Si addition has also been reported. However, interactions between silicic acid and Cd, Cu, and Pb at undersaturation of their silicates and other mineral phases remains elusive. Silicic acid, which is dissolved Si, may interact with cationic PTEs in soil, altering their environmental fate. At oversaturation, PTEs and silicic acid may precipitate forming metal silicates, whereas at undersaturation PTEs may be incorporated into the network of polymerized silicic acid or inner-spherically complexed on the negatively charged surface of polymeric silicic acid, forming particulate Si-contaminant compounds. Aiming to elucidate the extent and the mechanism of the potential PTE immobilization, long-term formation experiments in aqueous solution, a soil column experiment, and batch adsorption experiments including isothermal titration calorimetry (ITC) experiments were conducted. Long-term formation experiments in aqueous solution were conducted at undersaturation of PTE silicates and other mineral phases. Time-dependent particle size and charge changes were measured in between 211 days using dynamic light scattering and phase analysis light scattering. Solid phases were characterized by Fourier transform infrared (FTIR) spectroscopy and 29Si nuclear magnetic resonance (NMR) spectroscopy. Particle size measurements revealed a positive effect of cationic PTEs on silicic acid polymerization (Cu>Cd>Pb). However, only traces (2.1‰ Cd, 2‰ Cu and 1.4‰ Pb of the initially added PTEs) were bound during the polymerization of silicic acid. Copper was incorporated in the polymeric network of silicic acid during its polymerization as indicated by FTIR spectra and 29Si NMR relaxation experiments. Cadmium was only outer-spherically adsorbed. The long-term formation experiments revealed that particulate compounds form due to silicic acid/PTE interactions at undersaturation of other mineral phases. Soil column experiments were conducted to investigate the formation of Si-contaminant compounds in an acidic soil (pH 4.6). Therefore, a Haplic Phaeozem was preconditioned with Cu and Cd in the absence and presence of additional monomeric silicic acid and subsequently irrigated with artificial rainwater. Interactions of silicic acid and PTEs were investigated by monitoring the elemental composition of the eluates, and the size and charge of the particles eluted. After irrigation, total and exchangeable Si and PTE contents were analysed. Silicic acid application resulted in larger particles in the eluates, indicating silicic acid polymerization. The molar metal:Si ratios of the eluates and the significant correlation between Si and exchangeable metals indicated that particularly Cu formed Si-contaminant compounds in the soil, enhancing its retention. However, translocation of PTEs in particulate form, associated with polymerized silicic acid, was indicated. The negative charge and the very small size of the formed compounds may facilitate translocation from soil into groundwater. Batch adsorption experiments and ITC experiments were conducted to examine mechanism and extent of PTE adsorption to polymeric silicic acid. These experiments did not reveal any adsorption of the metals on polymeric silicic acid at pH 4 to 6 and after 24 h, which was underpinned by the results of the ITC experiments. However, zeta-potential measurements indicated weak electrostatic interactions between the negatively charged silanol groups and the PTEs. These electrostatic interactions may be the initial step of Si-contaminant compound formation. This thesis elucidates extent and mechanisms of silicic acid, either mono- or polymeric, and PTE interactions, showing the formation of particulate compounds from the reaction between silicic acid and cationic PTEs in aqueous solution and in an acidic soil. Particularly Cu formed stable compounds during silicic acid polymerization. However, the interactions showed a low extent and mainly weak electrostatic interactions, concluding that the addition of monomeric silicic acid to acidic soils may not be a quantitatively effective measure to reduce PTE mobility in soils. Aggregation effects, resulting from freezing/thawing or drying/rewetting, however, could alter the mobility of Si-contaminant compounds. These effects may be subject of future research, as well as the spectroscopic detection of Si-contaminant compounds in soils.
Entscheidungsorientierte Bewertung zur Preisobergrenzenbestimmung von Sponsoringengagements
(2023) Brian, Kevin; Troßmann, Ernst
Sponsoringengegaments sind ein weit verbreitetes Kommunikationsinstrument, mit denen eine ganze Reihe spezifischer betrieblicher Zielsetzungen in Verbindung gebracht werden. Die Anzahl und die hierarchische Struktur der identifizierten Ziele nehmen entscheidenden Einfluss auf die Zweckmäßigkeit der Bewertungsmethodik. Überlegungen zu dieser Hierarchie unter Berücksichtigung des sich im Planungsprozess entwickelnden Informationsstandes führen in der vorliegenden Arbeit zu einer Trennung der methodischen Behandlung der Bewertung zur Auswahlentscheidung aus mehreren Sponsoringalternativen und der Bewertung zur Durchführungsentscheidung, an deren Ende ein monetärer Wert als Preisgrenze steht. Im Rahmen der Auswahlentscheidung wird ein multikriterieller Bewertungsansatz ausgestaltet, der methodisch dem Konzept der Nutzwertanalyse folgt. Mit dem Ergebnis der Auswahlentscheidung als Ausgangspunkt, werden die Konsequenzen der Entscheidung monetarisiert, um – dem Kapitalwertkalkül folgend – die finanzielle Vorteilhaftigkeit in einem Simulationsmodell als Basis der Durchführungsentscheidung berechnen zu können.
Development and optimisation of a low-temperature drying schedule for Eucalyptus grandis (Hill) ex Maiden in a solar-assisted timber dryer
(2006) Bauer, Konrad; Mühlbauer, Werner
The Brazilian furniture industry consumes about 45 million m³ of sawnwood per year which is mainly supplied by deforestation of the tropical rainforest. At the same time, fast growing eucalypt species are produced on almost 3 million ha for the production of wood pulp and charcoal. Meanwhile, several Brazilian companies try to substitute the expensive natural woods by hardwood from eucalypt trees for the production of high quality sawnwood. However, eucalypt wood has to be dried very carefully under controlled conditions to prevent drying defects. Ambient air drying is not suitable since missing control causes high losses and long drying times. Beside this, the low wood moisture content required in the furniture industry cannot be achieved. Artificial drying technologies reduce the drying time, the timber can be dried to a low wood moisture content and the quality can be improved. However, sophisticated high-temperature dryers cause high investments. Locally manufactured timber dryers do not allow an adequate control of the drying process. Furthermore, the required slow drying process is increasing the thermal and electrical energy consumption causing high drying costs. To overcome the existing problems, the Institute of Agricultural Engineering in the Tropics and Subtropics of the University of Hohenheim (ATS) developed in close co-operation with the German company THERMO-SYSTEM Industrie- & Trocknungstechnik Ltd (THS), Alfdorf and the Brazilian forest company CAF Santa Barbara Ltda (CAF) a solar-assisted dryer for sawnwood with integrated solar collector and biomass backup heating system. Aim of this research work was to analyse the newly developed solar dryer and to develop a suitable drying schedule which allows the economical production of high quality sawnwood for the furniture industry. Therefore, a prototype of the greenhouse type dryer was installed under subtropical climate in Brazil. Due to the low thermal insulation of the solar dryer and missing experience with the extremely sensitive Brazilian varieties of Eucalyptus grandis, a new type of drying schedule had to be developed. The new schedule considers not only the general drying demands of eucalypt sawnwood but also the system immanent characteristics of the solar dryer and the ambient air conditions. An oscillation of the drying air temperature according to the ambient air allowed to speed up the drying process and reduces the condensation of water on the cover without a negative impact on the timber quality. In more than 80 drying tests with 16 000 m³ of eucalypt sawnwood the schedule was tested and improved. Based on experiments and information from literature, the course of the temperature, relative humidity and velocity of the drying air and the mode of remoistening was systematically optimised. Thereby, the influence of the changing drying conditions on the drying time, the timber quality, the energy consumption and the drying costs were analysed. With the final version of the drying schedule, 27 mm thick boards could be dried in the solar dryer from a medium wood moisture content of 60 to 12 % d.b. in 27 days. This drying time was about 20 % higher than in a high temperature dryer. However, a drying time of at least 60 days was required to reduce the moisture content to about 20 % d.b. at ambient air drying. The electric energy consumption in the solar dryer was reduced to about 20 kWh per m³ dried eucalypt sawnwood. This is only 20 % of the energy usually consumed in a high temperature dryer. The thermal energy consumption was 1.2 GJ per m³ which is about 60 % less than the energy required in conventional high temperature dryers. The low thermal and electrical energy consumption combined with the considerable lower investment costs for the solar-assisted timber resulted in average drying costs of 7.90 Euro per m³. This is only half of the costs caused by drying 27 mm thick eucalypt hardwood in a high temperature dryer. For an economic evaluation, a sensitivity analysis was done for the most important cost parameters. The electrical energy costs, the currency exchange rate and the interest rate for credits were found to be the main influencing parameters on the Brazilian market conditions. However, solar drying was generally more cost efficient than conventional high temperature drying. In the framework of this research work, it was proved that Brazilian eucalypt timber can be dried economically to a low moisture content of 10 to 12 % at a high quality level by applying the developed drying schedule in the optimised solar-assisted dryer. Meanwhile, approximately 35 000 m³ of eucalypt hardwood is dried annually in two solar-assisted drying plants contributing significantly to the protection of the natural rain forests.