Influence of different SSF conditions on ethanol production from corn stover at high solids loadings

In this study, three different kinds of simultaneous saccharification and fermentation (SSF) of washed pretreated corn stover with water-insoluble solids (WIS) content of 20% were investigated to find which one resulted in highest ethanol yield at high-solids loadings. The different methods were batch SSF, prehydrolysis followed by batch SSF and fed-batch SSF. Batch-SSF resulted in an ethanol yield of 75–76% and an ethanol concentration of 53 g/L. Prehydrolysis prior to batch SSF did not improve the ethanol yield compared with batch SSF. Fed-batch SSF, on the other hand, increased the yield, independent of the feeding conditions used (79–81%, 57–60 g/L). If the initial amount of solids during fed-batch SSF was lowered, the yield could be improved to some extent. When decreasing the enzyme dosage, the greatest decrease in yield was seen in the fed-batch mode (75%), while lower or the same yield was seen in batch mode with and without prehydrolysis (73%). This resulted in similar ethanol yields in all methods. However, the residence time to achieve the final ethanol yield was shorter using fed-batch. This shows that fed-batch can be a better alternative also at a lower enzyme loading

Acoustic assembly of cell spheroids in disposable capillaries

Multicellular spheroids represent a promising approach to mimic 3D tissues in vivo for emerging applications in regenerative medicine, therapeutic screening, and drug discovery. Conventional spheroid fabrication methods, such as the hanging drop method, suffer from low-throughput, long time, complicated procedure, and high heterogeneity in spheroid size. In this work, we report a simple yet reliable acoustic method to rapidly assemble cell spheroids in capillaries in a replicable and scalable manner. Briefly, by introducing a coupled standing surface acoustic wave, we are able to generate a linear pressure node array with 300 trapping nodes simultaneously. This enables us to continuously fabricate spheroids in a high-throughput manner with minimal variability in spheroid size. In a proof of concept application, we fabricated cell spheroids of mouse embryonic carcinoma (P19) cells, which grew well and retained differentiation potential in vitro. Based on the advantages of the non-invasive, contactless and label-free acoustic cell manipulation, our method employs the coupling strategy to assemble cells in capillaries, and further advances 3D spheroid assembly technology in an easy, cost-efficient, consistent, and high-throughput manner. This method could further be adapted into a novel 3D biofabrication approach to replicate compilated tissues and organs for a wide set of biomedical applications

Selectivity of natural, synthetic and environmental estrogens for zebrafish estrogen receptors.

International audience: Zebrafish, Danio rerio, is increasingly used as an animal model to study the effects of pharmaceuticals and environmental estrogens. As most of these estrogens have only been tested on human estrogen receptors (ERs), it is necessary to measure their effects on zebrafish ERs. In humans there are two distinct nuclear ERs (hERα and hERβ), whereas the zebrafish genome encodes three ERs, zfERα and two zfERβs (zfERβ1 and zfERβ2). In this study, we established HeLa-based reporter cell lines stably expressing each of the three zfERs. We first reported that estrogens more efficiently activate the zfERs at 28°C as compared to 37°C, thus reflecting the physiological temperature of zebrafish in wildlife. We then showed significant differences in the ability of agonist and antagonist estrogens to modulate activation of the three zfER isotypes in comparison to hERs. Environmental compounds (bisphenol A, alkylphenols, mycoestrogens) which are hER panagonists and hERβ selective agonists displayed greater potency for zfERα as compared to zfERβs. Among hERα selective synthetic agonists, PPT did not activate zfERα while 16α-LE2 was the most zfERα selective compound. Altogether, these results confirm that all hER ligands control in a similar manner the transcriptional activity of zfERs although significant differences in selectivity were observed among subtypes. The zfER subtype selective ligands that we identified thus represent new valuable tools to dissect the physiological roles of the different zfERs. Finally, our work also points out that care has to be taken in transposing the results obtained using the zebrafish as a model for human physiopathology

Disruption of VEGFR signaling leading to developmental defects

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Genome-Wide Search Reveals the Existence of a Limited Number of Thyroid Hormone Receptor Alpha Target Genes in Cerebellar Neurons

Thyroid hormone (T3) has a major influence on cerebellum post-natal development. The major phenotypic landmark of exposure to low levels of T3 during development (hypothyroidism) in the cerebellum is the retarded inward migration of the most numerous cell type, granular neurons. In order to identify the direct genetic regulation exerted by T3 on cerebellar neurons and their precursors, we used microarray RNA hybridization to perform a time course analysis of T3 induced gene expression in primary cultures of cerebellar neuronal cell. These experiments suggest that we identified a small set of genes which are directly regulated, both in vivo and in vitro, during cerebellum post-natal development. These modest changes suggest that T3 does not acts directly on granular neurons and mainly indirectly influences the cellular interactions taking place during development

Evaluation of Pretreatment and Process Configurations for Combined Ethanol and Biogas Production from Lignocellulosic Biomass

In view of global climate change and the increasing energy demand there is a need for renewable energy resources. This thesis discusses an energy-driven biorefinery concept based on the agricultural residues corn stover and wheat straw. The work is divided into two main parts. The first part is concerned with the effects of steam pretreatment and choice of acid catalyst on ethanol and biogas production, as well as the overall energy yield. The second part focuses on the combination of acetic-acid-catalysed steam pretreatment and simultaneous saccharification and co-fermentation (SSCF) and the role of process configuration on SSCF.Steam pretreatment was found to be a useful instrument to improve access of the main components of corn stover. This pretreatment resulted in high energy recovery. The choice of catalyst during steam pretreatment affected the overall energy recovery and product yield. Steam pretreatment with acetic acid or sulphuric acid improved the energy recovery compared with steam pretreatment with no catalyst or phosphoric acid. Phosphoric acid had toxic effects on ethanol and biogas production, while acetic acid was toxic only to ethanol production. The toxic effects on ethanol production were overcome by increasing the pH from 5.0 to 5.5. Process configuration also influenced the total energy recovery and product yield. This showed that not only the type of pretreatment, but also the process configuration, is important in an energy-driven biorefinery.Acetic acid is a known inhibitor during ethanol production. Using the S. cerevisiae strain KE6-12b resulted in ethanol production from both glucose and xylose, despite the fact that acetic-acid-catalysed steam pretreatment was used. Fed-batch improved SSCF in terms of ethanol yield and final ethanol concentration. Increasing the water insoluble solids (WIS) concentration from 10% to 11.7% improved the ethanol concentration, but the higher amount of inhibitors had a negative effect on the ethanol yield. Increasing the yeast concentration improved the results with higher WIS, but improvements are still required to increase the ethanol yield and concentration