Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Modeling of industrial-scale anaerobic solid-state fermentation for Chinese liquor production
    Jin, Guangyuan ; Uhl, Philipp ; Zhu, Yang ; Wijffels, René H. ; Xu, Yan ; Rinzema, Arjen - \ 2020
    Chemical Engineering Journal 394 (2020). - ISSN 1385-8947
    Chinese liquor - Heat transfer - Mathematical modeling - Product inhibition - Solid-state fermentation - Temperature modeling

    Traditional solid-state fermentation processes can give fluctuating product quality and quantity due to difficulties in control and scale up. This paper describes an engineering study of an industrial-scale anaerobic solid-state fermentation process for Chinese liquor (Baijiu) production, aimed at better understanding of the traditional process, as an initial step for future optimization. This mixed-culture fermentation is done in 0.44-m3 vessels embedded in the soil. At this scale, the fermentation is limited by product inhibition. We developed mathematical models based on the Han-Levenspiel equation for product inhibition, with parameters derived from measured data. The models accurately predicted the concentrations of starch and dry matter. A model with radial conduction into a small soil volume around the fermenter and consecutive vertical conduction into the underlying soil accurately predicted the pit temperature in the heating and cooling phases. This model is very sensitive to the values used for the enthalpies of combustion, meaning that direct measurement of the heat production rate would be preferable. In the industry practice, the fermenter volume can be from around 0.20 to 15.00 m3. The model predicts that overheating will occur not only in larger fermenters, but also in the 0.44-m3 fermenters when the soil temperature is high in summer. Our model predictions are consistent with observed behavior in the industry. Our findings can be used to improve this traditional process, as well as similar systems.

    Basic Phytochrome B Calculations
    Smith, Robert W. ; Fleck, Christian - \ 2019
    In: Phytochromes / Hiltbrunner, Andreas, Humana Press Inc. (Methods in Molecular Biology ) - ISBN 9781493996117 - p. 121 - 133.
    Computer programming - Mathematical modeling - Ordinary differential equations - Phytochromes

    Mathematical models are important tools in helping us to understand complex biological systems. Models of phytochrome-regulated systems in Arabidopsis thaliana have shown the importance of dimerization, nuclear transport, and thermal/dark reversion in mediating phytochrome activity and plant development. Here we go through the steps required to calculate the steady-state amounts of phytochrome subspecies relative to the total phytochrome molecule population. Starting from a simplified two-state system we expand and apply the technique to the extended phytochrome dimer model. Additionally, we provide a Python package that can automatically calculate the proportion of phytochrome B in a particular state given specific experimental conditions.

    Short lifespans of memory T-cells in bone marrow, blood, and lymph nodes suggest that T-cell memory is maintained by continuous self-renewal of recirculating cells
    Baliu-Piqué, Mariona ; Verheij, Myrddin W. ; Drylewicz, Julia ; Ravesloot, Lars ; Boer, Rob J. de; Koets, Ad ; Tesselaar, Kiki ; Borghans, José A.M. - \ 2018
    Frontiers in Immunology 9 (2018)SEP. - ISSN 1664-3224
    Bone marrow - Deuterium - Lifespan - Lymphocyte turnover - Mathematical modeling - Memory T-cells - Stable isotope labeling

    Memory T-cells are essential to maintain long-term immunological memory. It is widely thought that the bone marrow (BM) plays an important role in the long-term maintenance of memory T-cells. There is controversy however on the longevity and recirculating kinetics of BM memory T-cells. While some have proposed that the BM is a reservoir for long-lived, non-circulating memory T-cells, it has also been suggested to be the preferential site for memory T-cell self-renewal. In this study, we used in vivo deuterium labeling in goats to simultaneously quantify the average turnover rates-and thereby expected lifespans-of memory T-cells from BM, blood and lymph nodes (LN). While the fraction of Ki-67 positive cells, a snapshot marker for recent cell division, was higher in memory T-cells from blood compared to BM and LN, in vivo deuterium labeling revealed no substantial differences in the expected lifespans of memory T-cells between these compartments. Our results support the view that the majority of memory T-cells in the BM are self-renewing as fast as those in the periphery, and are continuously recirculating between the blood, BM, and LN.

    Paracrine mechanisms in early differentiation of human pluripotent stem cells : Insights from a mathematical model
    Gaspari, Erika ; Franke, Annika ; Robles-Diaz, Diana ; Zweigerdt, Robert ; Roeder, Ingo ; Zerjatke, Thomas ; Kempf, Henning - \ 2018
    Stem Cell Research 32 (2018). - ISSN 1873-5061 - p. 1 - 7.
    Differentiation - Human pluripotent stem cells - Mathematical modeling - Paracrine effects - Primitive streak

    With their capability to self-renew and differentiate into derivatives of all three germ layers, human pluripotent stem cells (hPSCs) offer a unique model to study aspects of human development in vitro. Directed differentiation towards mesendodermal lineages is a complex process, involving transition through a primitive streak (PS)-like stage. We have recently shown PS-like patterning from hPSCs into definitive endoderm, cardiac as well as presomitic mesoderm by only modulating the bulk cell density and the concentration of the GSK3 inhibitor CHIR99021, a potent activator of the WNT pathway. The patterning process is modulated by a complex paracrine network, whose identity and mechanistic consequences are poorly understood. To study the underlying dynamics, we here applied mathematical modeling based on ordinary differential equations. We compared time-course data of early hPSC differentiation to increasingly complex model structures with incremental numbers of paracrine factors. Model simulations suggest at least three paracrine factors being required to recapitulate the experimentally observed differentiation kinetics. Feedback mechanisms from both undifferentiated and differentiated cells turned out to be crucial. Evidence from double knock-down experiments and secreted protein enrichment allowed us to hypothesize on the identity of two of the three predicted factors. From a practical perspective, the mathematical model predicts optimal settings for directing lineage-specific differentiation. This opens new avenues for rational stem cell bioprocessing in more advanced culture systems, e.g. in perfusion-fed bioreactors enabling cell therapies.

    Theoretical approaches to understanding root vascular patterning : A consensus between recent models
    Mellor, Nathan ; Adibi, Milad ; El-Showk, Sedeer ; Rybel, Bert De; King, John ; Mähönen, Ari Pekka ; Weijers, Dolf ; Bishopp, Anthony ; Etchells, Peter - \ 2017
    Journal of Experimental Botany 68 (2017)1. - ISSN 0022-0957 - p. 5 - 16.
    Auxin - Cytokinin - Mathematical modeling - Organ patterning - Systems biology - Vascular development

    The root vascular tissues provide an excellent system for studying organ patterning, as the specification of these tissues signals a transition from radial symmetry to bisymmetric patterns. The patterning process is controlled by the combined action of hormonal signaling/transport pathways, transcription factors, and miRNA that operate through a series of non-linear pathways to drive pattern formation collectively. With the discovery of multiple components and feedback loops controlling patterning, it has become increasingly difficult to understand how these interactions act in unison to determine pattern formation in multicellular tissues. Three independent mathematical models of root vascular patterning have been formulated in the last few years, providing an excellent example of how theoretical approaches can complement experimental studies to provide new insights into complex systems. In many aspects these models support each other; however, each study also provides its own novel findings and unique viewpoints. Here we reconcile these models by identifying the commonalities and exploring the differences between them by testing how transferable findings are between models. New simulations herein support the hypothesis that an asymmetry in auxin input can direct the formation of vascular pattern. We show that the xylem axis can act as a sole source of cytokinin and specify the correct pattern, but also that broader patterns of cytokinin production are also able to pattern the root. By comparing the three modeling approaches, we gain further insight into vascular patterning and identify several key areas for experimental investigation.

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