18 research outputs found
Impact of sorbic acid and other mild preservation stresses on germination and outgrowth of Bacillus cereus spores
No full text Weak organic acids such as sorbic acid, lactate, and acetic acid are widely used by the food industry as preservatives to control growth of micro-organisms. With the current trend towards milder processing of food products, opportunities arise for spore-forming spoilage and pathogenic microorganisms such as Bacillus cereus, that may survive the use of milder heating regimes. Dormant spores produced by B. cereus can survive processing conditions and their subsequent outgrowth increases the risk of premature spoilage and food safety issues. As a consequence, the use of additional preservation hurdles, such as acidification with weak organic acid additives to ensure the quality and safety of a product is important. Sorbic acid is widely used as an antimicrobial compound because of its strong inhibitory properties against bacteria and other spoilage organisms. Its effectivity has also been ascribed to its hydrophobic character, resulting in an additional mode of action not observed with other less lipophilic organic acids such as lactic acid and acetic acid. In this project the impact of sorbic acid on spore germination and outgrowth was studied at transcriptome level and was linked to the distinct phenotypic responses observed for spores exposed to different levels of sorbic acid. The various stages of spore germination and outgrowth could be recognized by distinct gene expression profiles representing either the germination phase, transition state between germination and outgrowth or outgrowing cells, respectively. A subset of genes was specifically expressed in sorbic acid-exposed germinating spores and included functions related to cell envelope, (multi) drug transporters and amino acid metabolism. At high concentrations of sorbic acid (3mM of the undisssociated form, HSA), nutrient-induced germination of B. cereus ATCC 14579 spores was completely blocked. This blockage was shown to be reversible and could be bypassed by known non-nutrient triggers that activate spores in a receptor-independent way, pointing to a possible interference of HSA with the signaling event between germinant receptors and proposed SpoVA-channels, possibly by accumulation into the spore’s inner membrane. Additional experiments with other inhibiting compounds, including organic acids and their structurally similar alcohol counterparts, showed that the lipophilic properties are an important determinant of its efficacy to block germination. Building on current knowledge on the interaction of germination-relevant protein clusters, we discuss a hypothetical model on the mode of action of sorbic acid and other short-chain lipophilic compounds in germination inhibition of B. cereus spores. In addition to the interference or even blockage of germination, sorbic acid may increase outgrowth heterogeneity when applied at lower concentrations (0.25-1.5 mM) that still allow outgrowth. The first stages of outgrowth were shown to specifically occur heterogeneously when spores were exposed to multiple stresses simultaneously. Heterogeneity effects were most pronounced for combined stress-effects where heat-treated spores were also exposed to low pH stress. Under these conditions, a large subpopulation of spores was delayed between initial germination and swelling and further outgrowth. For the food producing industry, it would be desirable to have reliable parameters to predict the behavior of surviving spores in a food product. Data presented in this thesis show that germination rate is not a good predictor for outgrowth heterogeneity when applied as a single indicator. In conclusion, the work described in this thesis strive to obtain a better understanding on the impact that preservation stresses, including (sorbic) acid stress, have on the germination and outgrowth (heterogeneity) of B. cereus spores. The results obtained in this project may contribute to the rational design of new concepts for improved food preservation and safety.</p
Impact of sorbic acid on germinant receptor-dependent and -independent germination pathways in Bacillus cereus
No full textAmino acid- and inosine-induced germination of Bacillus cereus ATCC 14579 spores was reversibly inhibited in the presence of 3 mM undissociated sorbic acid. Exposure to high hydrostatic pressure, Ca-dipicolinic acid (DPA), and bryostatin, an activator of PrkC kinase, negated this inhibition, pointing to specific blockage of signal transduction in germinant receptor-mediated germination
In-situ impact analysis during fatigue tests of open-hole carbon fibre reinforced polymer specimens
No full textThis paper presents the results for an experimental campaign of in-situ impact during tension-tension fatigue loading for open-hole carbon fibre reinforced polymer specimens. High-speed low energy impact was introduced to the specimen with the use of a canon, which was attached to testing bench enabling the impact without the need to remove the specimens from the test bench. Digital Image Correlation, C-scan and Acoustic Emission were utilized to record health monitoring data for damage diagnostics. A strain-based criterion was used to identify a common threshold for the timing of impact ensuring a fair comparison between the different tests. The results indicate that while an impact causes the total amount of damage to increase as one would expect, it does not necessarily increase the damage level in the critical area where final fracture occurs. A dependence on the moment of impact with the fatigue failure was found for specimens subjected to impact before the initiation of the fatigue loading. In contrast, impacting specimens in the presence of fatigue damage had no detrimental effect on the fatigue life, although it was observed that the damaged area was enlarged. Overall, the paper showcases the need to study systemically the effect of in-situ impact on the fatigue life in order to understand better the implications that may be introduced to the integrity of a composite structure.Structural Integrity & Composite
Architectural Pipeline - Pipeline Architecture: An experiment into the role of topological graphs in the early stages of architectural design in the era of machine learning
No full textThe realm of architectural design and conceptualization, despite witnessing advancements in design complexity facilitated by technological tools and fabrication techniques, appears to have experienced limited transformative change over time in the way we begin our design process. But is there an alternative way to look at architecture ? Perhaps a completely different way to begin a project ? Can the age of data abundance cause a shift in the way we look at architectural design ?Architecture, Urbanism and Building Sciences | Explorela
Impact of sorbic acid on germinant receptor-dependent and -independent germination pathways in Bacillus cereus
No full textAmino acid- and inosine-induced germination of Bacillus cereus ATCC 14579 spores was reversibly inhibited in the presence of 3 mM undissociated sorbic acid. Exposure to high hydrostatic pressure, Ca-dipicolinic acid (DPA), and bryostatin, an activator of PrkC kinase, negated this inhibition, pointing to specific blockage of signal transduction in germinant receptor-mediated germination
Computer Vision and Human–Robot Collaboration Supported Design-to-Robotic-Assembly
No full textWhile half of all construction tasks can be fully automated the other half relies to a certain degree on human support. This paper presents a Computer Vision (CV) and Human–Robot Interaction/Collaboration (HRI/C) supported Design-to-Robotic-Assembly (D2RA) approach that links computational design with robotic assembly. This multidisciplinary approach has been tested on a case study focusing on urban furniture and involving experts from respective disciplines and students
SSIG: A Visually-Guided Graph Edit Distance for Floor Plan Similarity
No full textWe propose a simple yet effective metric that measures structural similarity between visual instances of architectural floor plans, without the need for learning. Qualitatively, our experiments show that the retrieval results are similar to deeply learned methods. Effectively comparing instances of floor plan data is paramount to the success of machine understanding of floor plan data, including the assessment of floor plan generative models and floor plan recommendation systems. Comparing visual floor plan images goes beyond a sole pixel-wise visual examination and is crucially about similarities and differences in the shapes and relations between subdivisions that compose the layout. Currently, deep metric learning approaches are used to learn a pair-wise vector representation space that closely mimics the structural similarity, in which the models are trained on similarity labels that are obtained by Intersection-over-Union (IoU). To compensate for the lack of structural awareness in IoU, graph-based approaches such as Graph Matching Networks (GMNs) are used, which require pairwise inference for comparing data instances, making GMNs less practical for retrieval applications. In this paper, an effective evaluation metric for judging the structural similarity of floor plans, coined SSIG (Structural Similarity by IoU and GED), is proposed based on both image and graph distances. In addition, an efficient algorithm is developed that uses SSIG to rank a large-scale floor plan database. Code will be openly available.The version of this article that was uploaded to the research portal is an open access version of the IEEE Computer Society version that was uploaded in December 2023. There is a slight discrepancy between the page numbers of the definitive version (pp. 1565-1574) and the open access version (pp. 1573-1582).Building KnowledgePattern Recognition and Bioinformatic
Germination inhibition of Bacillus cereus spores: impact of the lipophilic character of inhibiting compounds.
No full textIn this study, the impact of a range of organic acids and structurally similar alcohols with three to six carbon backbones and increasing lipophilic character, were tested on the germination behavior of B. cereus ATCC 14579 spores. This approach allowed substantiating whether the effectivity of the various compounds was largely dictated by membrane interference or a classic weak acid acidification effect. The octanol-water partition coefficient (log P oct/water) ranges from 0.25/0.33 to 2.03/1.96 for propanol/undissociated propionic acid and hexanol/undissociated hexanoic acid, respectively. Performance of germination assays at neutral (pH7) and acidic conditions (pH5.5) allowed for a comparative analysis of the action of dissociated versus undissociated acids, and the presumed pH-independent effect of the corresponding alcohols. Germination assays, based on both continuously measured optical density and time-based plating experiments, and microscopic observations demonstrated the correlation between the lipophilic character of the selected compounds and their inhibiting effect on spore germination. Real-time fluorescence based assays showed that membrane integrity in dormant spores was maintained in the presence of the tested inhibitors. Lowering the critical concentration of inhibitors by a one-step washing procedure resulted in the onset of nutrient-induced germination, indicating the reversible nature of the inhibition process. Furthermore, blocking of nutrient-induced germination in the presence of inhibitory concentrations of selected lipophilic acids and corresponding alcohols was by-passed upon addition of Ca-dipicolinic acid, pointing to loss of signaling capacity in germinant receptor-mediated germination activity. These findings show that lipophilicity is an important determinant for the ability of the selected acids and corresponding alcohols to accumulate in the spore inner membrane and their ability to act as a germination-inhibitor. © 2012 Elsevier B.V
Advancing Applications for Artificial-Intelligence-Supported Ambient Control in the Built Environment
No full textAmbient intelligence (AmI) relying on electronic devices employing information and communication technology (ICT) and artificial intelligence (AI) embedded in the network connecting these devices tends today to be insufficiently used. This deficiency implies that spaces are uncomfortable and considerable energy dissipates due to distribution losses, excessive or unnecessary climate control of little- and unoccupied spaces, etc.Building operations are responsible for ±27% of annual carbon dioxide (CO2) emissions, and infrastructure materials and construction are responsible for an additional ±13% annually; both need to be addressed integratively to meet sustainability goals. This paper addresses this in three AI-supported AmI test simulations of applications focusing on illumination and ventilation systems embedded in the built environment.Building Knowledg
Analysis of acid-stressed Bacillus cereus reveals a major oxidative response and inactivation-associated radical formation
No full textAcid stress resistance of the food-borne human pathogen Bacillus cereus may contribute to its survival in acidic environments, such as encountered in soil, food and the human gastrointestinal tract. The acid stress responses of B. cereus strains ATCC 14579 and ATCC 10987 were analysed in aerobically grown cultures acidified to pH values ranging from pH 5.4 to pH 4.4 with HCI. Comparative phenotype and transcriptome analyses revealed three acid stressinduced responses in this pH range: growth rate reduction, growth arrest and loss of viability. These physiological responses showed to be associated with metabolic shifts and the induction of general stress response mechanisms with a major oxidative component, including upregulation of catalases and superoxide dismutases. Flow cytometry analysis in combination with the hydroxyl (OH center dot) and peroxynitrite (ONOO-)-specific fluorescent probe 3'-(phydroxyphenyl) fluorescein (HPF) showed excessive radicals to be formed in both B. cereus strains in bactericidal conditions only. Our study shows that radicals can indicate acid-induced malfunctioning of cellular processes that lead to cell death
