Quantitative Characterization of the Growth of Deinococcus geothermalis DSM-11302: Effect of Inoculum Size, Growth Medium and Culture Conditions

Due to their remarkable resistance to extreme conditions, Deinococcaceae strains are of great interest to biotechnological prospects. However, the physiology of the extremophile strain Deinococcus geothermalis has scarcely been studied and is not well understood. The physiological behaviour was then studied in well-controlled conditions in flask and bioreactor cultures. The growth of D. geothermalis type strains was compared. Among the strains tested, the strain from the German Collection of Microorganisms (Deutsche Sammlung von Mikroorganismen DSM) DSM-11302 was found to give the highest biomass concentration and growth rate: in a complex medium with glucose, the growth rate reached 0.75 h−1 at 45 °C. Yeast extract concentration in the medium had significant constitutive and catalytic effects. Furthermore, the results showed that the physiological descriptors were not affected by the inoculum preparation steps. A batch culture of D. geothermalis DSM-11302 on defined medium was carried out: cells grew exponentially with a maximal growth rate of 0.28 h−1 and D. geothermalis DSM-11302 biomass reached 1.4 g•L −1 in 20 h. Then, 1.4 gDryCellWeight of biomass (X) was obtained from 5.6 g glucose (Glc) consumed as carbon source, corresponding to a yield of 0.3 CmolX•CmolGlc−1 ; cell specific oxygen uptake and carbon dioxide production rates reached 216 and 226 mmol.CmolX −1•h −1 , respectively, and the respiratory quotient (QR) value varied from 1.1 to 1.7. This is the first time that kinetic parameters and yields are reported for D. geothermalis DSM-11302 grown on a mineral medium in well-controlled batch cultur

Transcriptomic Analyses during the Transition from Biomass Production to Lipid Accumulation in the Oleaginous Yeast Yarrowia lipolytica

We previously developed a fermentation protocol for lipid accumulation in the oleaginous yeast Y. lipolytica. This process was used to perform transcriptomic time-course analyses to explore gene expression in Y. lipolytica during the transition from biomass production to lipid accumulation. In this experiment, a biomass concentration of 54.6 gCDW/l, with 0.18 g/gCDW lipid was obtained in ca. 32 h, with low citric acid production. A transcriptomic profiling was performed on 11 samples throughout the fermentation. Through statistical analyses, 569 genes were highlighted as differentially expressed at one point during the time course of the experiment. These genes were classified into 9 clusters, according to their expression profiles. The combination of macroscopic and transcriptomic profiles highlighted 4 major steps in the culture: (i) a growth phase, (ii) a transition phase, (iii) an early lipid accumulation phase, characterized by an increase in nitrogen metabolism, together with strong repression of protein production and activity; (iv) a late lipid accumulation phase, characterized by the rerouting of carbon fluxes within cells. This study explores the potential of Y. lipolytica as an alternative oil producer, by identifying, at the transcriptomic level, the genes potentially involved in the metabolism of oleaginous species

Experimental and statistical analysis of nutritional requirements for the growth of the extremophile Deinococcus geothermalis DSM 11300

Few studies concerning the nutritional requirements of Deinococcus geothermalis DSM 11300 have been conducted to date. Three defined media compositions have been published for the growth of this strain but they were found to be inadequate to achieve growth without limitation. Furthermore, growth curves, biomass concentration and growth rates were generally not available. Analysis in Principal Components was used in this work to compare and consequently to highlight the main compounds which differ between published chemically defined media. When available, biomass concentration, and/or growth rate were superimposed to the PCA analysis. The formulations of the media were collected from existing literature; media compositions designed for the growth of several strains of Deinococcaceae or Micrococcaceae were included. The results showed that a defined medium adapted from Holland et al. (Appl Microbiol Biotechnol 72:1074–1082, 2006) was the best basal medium and was chosen for further studies. A growth rate of 0.03 h-1 and a final OD600nm of 0.55 were obtained, but the growth was linear. Then, the effects of several medium components on oxygen uptake and biomass production by Deinococcus geothermalis DSM 11300 were studied using a respirometry-based method, to search for the nutritional limitation. The results revealed that the whole yeast extract in the medium with glucose is necessary to obtain a non-limiting growth of Deinococcus geothermalis DSM 11300 at a maximum growth rate of 0.64 h-1 at 45 °C

Optical Methods and Their Limitation to Characterize the Morphology and Granulometry of Complex Shape Biological Materials

Background and aim: Particle size and morphology of biomass (microorganism, lignocellulosic substrates) stand out as the major determinants of the bioprocess efficiency. Through its impact on rheology, it affects momentum, heat and and mass transfers within the bioreactor. Various techniques are available to characterize in-situ and ex-situ size and shape of particles. The most common methods are classified into three groups: (i) analysis of microscopic images; (ii) laser light diffraction and (iii) settling kinetics. In present work, five techniques are compared and discussed with model particles, microorganisms and lignocellulosic substrates. Methods: The used techniques aim to characterize size and shape (0.1 to 2000µm). In-situ and ex-situ measurements were used: chord length measurement (FBRM), diffraction light scattering (DLS), morpho-granulometry (MG), cytometry (CYT) and settling velocity (TUL). A set of height polystyrene microspheres (1.0 to 15.0µm) and microbeads (40 and 80µm) were used as reference. Yarrowia lipolytica is strictly aerobic yeast, belonging to the family of hemiascomycetes. Cells are subjected to mycelial transition induced by pH changes. Its morphology evolves from ovoid shape (5-7µm) up to filament. It was used to appreciate the ability to qualify and quantify filamentous shape (width, length). Finally, two cellulosic matrices, microcrystalline cellulose and coniferous paper pulp were selected to investigate complex fiber morphologies. Results: Specifications and limits of instruments are scrutinized. Sampling methods and preparation should be carefully considered. Optical measurements provide raw data (light intensity, frequency, images) from which morphological parameters will be straightly extracted or calculated based on assumptions (optical properties, particles geometry, theory). Considering diameters and associated number and volume distribution functions, techniques are compared with model calibrated microspheres. The mean values appear consistent between techniques but the magnitude of standard deviation extensively varies. Few instruments (MG, CYT) provide access to additional morphological criteria (length, width, aspect ratio). Mycelial kinetics and magnitude is accurately described by fiber length (MG). However a poor reliability of width (time of flight, CYT) is noticeable. Considering more complex lignocellulosic particles, the relative diameter values usually indicate similar trends whatever the techniques is. However, absolute values should be carefully considered and may deviated in large extend (5-10 times)

Special Issue “Bioenergies, Present and Prospects”

Special Issue “Bioenergies, Present and Prospects

L'Electrode Poreuse Percolée Pulsée : Une conception nouvelle et efficace de traitement et de récupération des eaux résiduaires

International audienc

Biomasse : Pourquoi pas une raffinerie du végétal ?

International audienc

De la conversion microbienne des ressources lignocellulosiques pour la production de molécules énergétiques : verrous et perspectives

La production de « bioénergies » représente un défi important pour réduire les impacts environnementaux liés aux combustibles fossiles et accroitre l'indépendance énergétique. Cet article présente un état des lieux de la production de biocarburants (éthanol, lipides et hydrogène) par conversion de ressources lignocellulosiques par des levures ou des bactéries (conversion algale non traitée). Les étapes de prétraitements et hydrolyse nécessaires à l’obtention de substrats carbonés liquides et gazeux sont présentés et discutés. Cette revue montre les limites scientifiques et technologiques de cette conversion i.e. teneur initiale en carbone faible, génération d’inhibiteurs, limitations aux transferts gaz-liquide, faibles rendements en produits à partir du carbone initial. Les projets actuels s’intéressent au développement de souches génétiquement modifiées et de bioprocédés innovants pouvant ouvrir de nouvelles opportunités de production. La valorisation (matière et chaleur) et le recyclage des sous-produits contribueront à la viabilité économique et environnementale de la voie lignocellulosique de production d’agro-carburants.The production of bioenergies represents an important challenge to reduce environmental impacts linked to fossil fuels and to increase energetic independence. This article proposes an overview of biofuels’ production (ethanol, lipids and hydrogen mainly) by converting lignocellulosic resources using yeasts or bacteria (algal conversion is not considered). Both pretreatment and hydrolysis steps used to obtain liquid and gaseous substrates are presented and discussed. This review shows the scientific and technological bottlenecks of this conversion i.e. initial low carbon content, generation of inhibitors, limitations to gas-liquid transfers, low yields of products from the initial carbon. Current projects and prospects focus on the development of genetically modified strains and innovative bioprocesses that can offer new production opportunities. Matter and heat valorizations and recycling of by-products will contribute to the economic and environmental viability of the lignocellulosic pathway for the production of biofuels

Biomasse : Pourquoi pas une raffinerie du végétal ?

International audienc

Nouvelle technologie dans la récupération de cadmium

International audienc