Glucose derived from an industrial, enzymatically saccharified wheat starch fraction (B starch) was investigated for ethanol production using free and immobilized cells of Saccharomyces cerevisiae and Zymomonas mobilis. Batch cultures of these organisms could successfully ferment this substrate within 24 h giving 7% ethanol by volume and over 96% sugar conversion. Fermentation with S cerevisiae and Z. mobilis immobilized on rotating fiber discs in a continuous dynamic biocatalyst bioreactor (CDIBB) resulted in very rapid and efficient fermentation and concurrent high ethanol productivity. Z. mobilis loaded at 30g/I cell density (based on bioreactor volume, 31) fermented saccharified wheat starch B slurry at 15% solids and having 128g/I glucose, in 0.9 h with 92% sugar utilization; and volumetric productivity based on liquid hold up was 65.5 g/I‐h, being threefold higher than that obtained with immobilized yeast cells. Z. mobilis appears to be the preferred organism for the rapid fermentation of glucose rich solutions in the CDIBB. Advantages and the possible application of this bioreactor system to alcoholic fermentation of industrial derived substrates associated with high suspended solids are discussed. Die aus einer industriellen, enzymatisch verzuckerten Weizen‐B‐Stärke gewonnene Glucose wurde unter Verwendung von freien und immobilisierten Zellen von Saccharomyces cerevisiae und Zymomonas mobilis hinsichtlich der Ethanolgewinnung untersucht. Chargenweise Kulturen dieser Organismen vergoren dieses Substrat erfolgreich 24h; sie ergaben 7 Vol.% Ethanol bei 96% iger Zuckerumwandlung. Die Vergärung mit auf rotierenden Faserplatten immobilisierten S. cerevisiae und Z. mobilis in einem kontinuierlichen, dynamischen Biokatalysator‐Bioreaktor (CDIBB) führte zu sehr schneller und wirksamer Gärung und vergleichbar hoher Ethanolproduktivität. Mit einer Zelldichte von 30g/1 (bez. auf das Bioreaktorvolumen, 31) gepackte Z. mobilis vergor eine Weizen‐B‐Stärkesuspension mit 15% Feststoff und 128g Glucose/1 in 0,9h bei 92% Zuckerverwertung. Die Volumenproduktivität, bezogen auf die Flüssigkeitsrückhaltung, betrug 65,5 g/1‐h und war damit dreimal so hoch wie bei immobilisierten Hefezellen. Z. mobilis dürfte der bevorzugte Organismus für die rasche Vergärung von glucosereichen Lösungen im CDIBB sein. Die Vorteile und die mögliche Anwendung dieses Bioreaktorsystems für die alkoholische Vergärung von industriellen Substraten in Verbindung mit hoch suspendierten Feststoffen werden diskutiert.
Nuclear pore complexes (NPCs) mediate bidirectional nucleocytoplasmic transport of substances in eukaryotic cells. However, the accurate molecular arrangement of NPCs remains enigmatic owing to their huge size and highly dynamic nature. Here we determined the structure of the asymmetric unit of the inner ring (IR monomer) at 3.73 Å resolution by single-particle cryo-electron microscopy, and created an atomic model of the intact IR consisting of 192 copies from 8 subunits. In each IR monomer, two approximately parallel rhomboidal structures of the inner and outer layers are sandwiched with the Z-shaped Nup188-Nup192 middle layer and Nup188, Nup192 and Nic96 link all subunits to constitute a relatively stable IR monomer, while the intact IR is assembled by loose and instable interactions between IR monomer. These structures reveal various interaction modes and extensive flexible connections in the assembly, providing a structural basis for the stability and malleability of IR.One-Sentence SummaryAccurate structure of inner ring reveals its assembly and function in dilation and constriction of nuclear pore complex.
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