Lab-Scale Cultivation of Cupriavidus necator on Explosive Gas Mixtures: Carbon Dioxide Fixation into Polyhydroxybutyrate

Aerobic, hydrogen oxidizing bacteria are capable of efficient, non-phototrophic CO(2) assimilation, using H(2) as a reducing agent. The presence of explosive gas mixtures requires strict safety measures for bioreactor and process design. Here, we report a simplified, reproducible, and safe cultivation method to produce Cupriavidus necator H16 on a gram scale. Conditions for long-term strain maintenance and mineral media composition were optimized. Cultivations on the gaseous substrates H(2), O(2), and CO(2) were accomplished in an explosion-proof bioreactor situated in a strong, grounded fume hood. Cells grew under O(2) control and H(2) and CO(2) excess. The starting gas mixture was H(2):CO(2):O(2) in a ratio of 85:10:2 (partial pressure of O(2) 0.02 atm). Dissolved oxygen was measured online and was kept below 1.6 mg/L by a stepwise increase of the O(2) supply. Use of gas compositions within the explosion limits of oxyhydrogen facilitated production of 13.1 ± 0.4 g/L total biomass (gram cell dry mass) with a content of 79 ± 2% poly-(R)-3-hydroxybutyrate in a simple cultivation set-up with dissolved oxygen as the single controlled parameter. Approximately 98% of the obtained PHB was formed from CO(2)

Francophile contre vents et marées ? Otto Abetz et les Français, 1930 - 1958

J’ai rencontré Élisabeth en été 1998, lorsque je rejoignais mon compagnon – devenu mon mari depuis – qui était alors allocataire de recherche au CRFJ. Plongée au milieu de la difficile rédaction de ma thèse de doctorat, c’est au plus tard avec l’arrivée de l’hiver hiérosolomytain – et donc un certain froid pénétrant dans les maisons de la ville, souvent assez mal isolées – qu’Élisabeth m’a proposé de m’installer à un bureau libre au sein de la bibliothèque du Centre. Je lui dois une grande re..

PACER : a novel 3D plant cell wall model for the analysis of non-catalytic and enzymatic responses

Background Substrate accessibility remains a key limitation to the efficient enzymatic deconstruction of lignocellulosic biomass. Limited substrate accessibility is often addressed by increasing enzyme loading, which increases process and product costs. Alternatively, considerable efforts are underway world-wide to identify amorphogenesis-inducing proteins and protein domains that increase the accessibility of carbohydrate-active enzymes to targeted lignocellulose components. Results We established a three-dimensional assay, PACER (plant cell wall model for the analysis of non-catalytic and enzymatic responses), that enables analysis of enzyme migration through defined lignocellulose composites. A cellulose/azo-xylan composite was made to demonstrate the PACER concept and then used to test the migration and activity of multiple xylanolytic enzymes. In addition to non-catalytic domains of xylanases, the potential of loosenin-like proteins to boost xylanase migration through cellulose/azo-xylan composites was observed. Conclusions The PACER assay is inexpensive and parallelizable, suitable for screening proteins for ability to increase enzyme accessibility to lignocellulose substrates. Using the PACER assay, we visualized the impact of xylan-binding modules and loosenin-like proteins on xylanase mobility and access to targeted substrates. Given the flexibility to use different composite materials, the PACER assay presents a versatile platform to study impacts of lignocellulose components on enzyme access to targeted substrates.Peer reviewe