Optimization of a synthetic mixture composed of major Trichoderma reesei enzymes for the hydrolysis of steam-exploded wheat straw

<p>Abstract</p> <p>Background</p> <p>An efficient hydrolysis of lignocellulosic substrates to soluble sugars for biofuel production necessitates the interplay and synergistic interaction of multiple enzymes. An optimized enzyme mixture is crucial for reduced cost of the enzymatic hydrolysis step in a bioethanol production process and its composition will depend on the substrate and type of pretreatment used. In the present study, an experimental design was used to determine the optimal composition of a <it>Trichoderma reesei </it>enzyme mixture, comprising the main cellulase and hemicellulase activities, for the hydrolysis of steam-exploded wheat straw.</p> <p>Methods</p> <p>Six enzymes, CBH1 (Cel7a), CBH2 (Cel6a), EG1 (Cel7b), EG2 (Cel5a), as well as the xyloglucanase Cel74a and the xylanase XYN1 (Xyl11a) were purified from a <it>T. reesei </it>culture under lactose/xylose-induced conditions. Sugar release was followed in milliliter-scale hydrolysis assays for 48 hours and the influence of the mixture on initial conversion rates and final yields is assessed.</p> <p>Results</p> <p>The developed model could show that both responses were strongly correlated. Model predictions suggest that optimal hydrolysis yields can be obtained over a wide range of CBH1 to CBH2 ratios, but necessitates a high proportion of EG1 (13% to 25%) which cannot be replaced by EG2. Whereas 5% to 10% of the latter enzyme and a xylanase content above 6% are required for highest yields, these enzymes are predicted to be less important in the initial stage of hydrolysis.</p> <p>Conclusions</p> <p>The developed model could reliably predict hydrolysis yields of enzyme mixtures in the studied domain and highlighted the importance of the respective enzyme components in both the initial and the final hydrolysis phase of steam-exploded wheat straw.</p

Non-Invasive Exploration of Neonatal Gastric Epithelium by Using Exfoliated Epithelial Cells

Background &amp; Aims: In preterm infants, exfoliated gastric epithelial cells can be retrieved from aspirates sampled through the naso-gastric feeding tube. Our aims were to determine (1) whether the recovery of exfoliated cells is feasible at any time from birth through the removal of the nasogastric tube, (2) whether they can be grown in culture in vitro, and (3) whether the physiological state of exfoliated cells expressing H+/K+-ATPases reflects that of their counterparts remaining in situ at the surface of the gastric epithelium in neonatal rat pups. Methods: In infants, gastric fluid aspirates were collected weekly after birth or every 3 hours over 24-h periods, and related to clinical parameters (Biocollection PROG/09/18). In rat pups submitted to a single fasting/refeeding cycle, we explored circadian exfoliation with the cellular counter-parts in the gland. All samples were analyzed by confocal imaging and Enzyme-Linked Immunosorbent Assay. Results: Epithelial cells were identified by microscopy using membrane-bound anti-H+/K+ ATPases antibody, assessed for nucleus integrity, and the expression of selected proteins (autophagy, circadian clock). On 34 infants, the H+/K+-ATPasepositive cells were consistently found quiescent, regardless of gestational age and feeding schedule from day-5 of life to the day of removal of the naso-gastric tube. By logistic regression analysis, we did find a positive correlation between the intensity of exfoliation (cellular loss per sample) and the postnatal age (p,0.001). The H+/K+ ATPase-positive cell

Geochemistry and XRD to differentiate oolitic ironstone geological levels from Germany, Belgium and France and application to the archaeological artefacts

Particle Induced X-ray Emission (PIXE) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) have largely demonstrated their capability to analyse trace elements for determining the origin of archaeological materials. Trace elements can in fact be used as fingerprint of the geological origin and thus contribute to provenance investigations. This point is an important question for prehistoric studies, as it provides information on mobility, exchanges and interaction between groups of population. We present experimental PIXE configurations which allow to investigate prehistoric oolithic haematite, at the ppm level without any preparation or sampling. We compare the data obtained with two devices, namely AGLAE (Accélérateur Grand Louvre d'Analyse Elémentaire) in Paris and the cyclotron in the Centre Européen d'archéométrie in Liège and we determined the uncertainties of measures. The geological samples were compared in order to estimate de geochemical variability in stratigraphy and in width of oolithic haematite from the Ordovician in Caen region (France) and from the Devonian in Hesbaye (Belgium). These data were also compared to oolithic haematite used during Mesolithic and LBK (Early Neolithic) in both the regions. Furthermore we looked for mineralogical fingerprints by X-Ray Diffraction on disoriented powders. The mineralogical composition is ubiquitous and no discrimination between the stratigraphical layers was possible

Influence of the gonads and/or of LHRH analogue on gonadotropic function in testosterone-treated or untreated juvenile rainbow trout

International audienceThe influence of the gonads and/or of LHRH on gonadotropic function, and possibly on gonadal development, was studied in juvenile rainbow trout treated with low doses of testosterone or untreated. Whatever the treatment, all fish of both sexes remained sexually immature, although large individual variations in plasma GTH were observed in all experimental and control groups. This dispersion in the individual values of plasma GTH seemed to be the first sign of an increase in the previously low gonadotropic activity and might announce the beginning of a pubertal period several months before the onset of meiosis in males and of vitellogenesis in females. Castration did not change the plasma and pituitary GTH values, suggesting that control of the gonadotropic function did not depend mainly on sexual steroids during this period. In our experimental conditions, LHRH administration did not lead to any change in plasma or pituitary levels of GTH. Only the testosterone treatment (20 μg) had an effect, causing a higher pituitary GTH load in some fish which was not modified either by castration or by LHRH and decreased with time ; neither of these treatments changed the plasma GTH levels. Thus, the fact that the required amount of GTH was not released to initiate early onset of gametogenesis did not seem to be due to a repressive control by the gonads or to the absence of stimulation by an LHRH-like hypothalamic factor. The quantity of GTH accumulated in the pituitary gland and the dose of steroid used have been discussed

Influence of testosterone on precocious sexual development in immature rainbow trout

The influence of testosterone on plasma and pituitary levels of gonadotrophin (GTH) as well as on gonadal development was studied in immature rainbow trout. Among the animals receiving a testosterone-cocoa butter implant (200 μg) at the age of 5 months, gonadal puberty occurred 8 months later in half of the males (opposite to the controls which remained immature) and the beginning of oocyte maturation was observed in only one female. These animals were characterized by a higher pituitary GTH level. Owing to the multivariate statistical analyses made, it was possible to provide evidence for the presence of two populations with different reactions to the same steroid treatment. They also confirmed the existence of a positive testosterone feedback, in the male, leading to a precocious gonadal development. The pituitary GTH load obtained with 200 μg of testosterone seemed to be related to the age at first maturation. The secretion of an appropriate level of GTH resulting in the stimulation of gametogenesis required the availability of a relatively large pituitary GTH level and seemed to be possible because the animals were already in the pubertal period. The fact that the highest pituitary GTH level of the treated lot was found in the only female showing a beginning of sexual maturation suggests that testosterone may also act in females

Uranyl Complexation in Fluorinated Acids (HF, HBF4_4, HPF6_6, HTf2_2N): A Combined Experimental and Theoretical Study

The aim of this work is to characterize the complexation ability of F^-, BF_4^-, PF_6^-, and Tf_2N^- toward uranyl ions in aqueous solution. These anions were chosen as they represent the anionic part of the most studied room-temperature ionic liquids. Time-resolved emission spectroscopy and X-ray absorption spectroscopy were used to retrieve structural data on the complexes formed. The results obtained were compared with computational data. Tf_2N^- does not complex uranyl, even at high concentration. Other fluorinated acids form inner-sphere complexes with U(VI), in a monodentate fashion in the case of BF_4^- and PF_6^-

Identification of antibiotics triggering the dissemination of antibiotic resistance genes by SXT/R391 elements using a dedicated high-throughput whole-cell biosensor assay

International audienceAbstract Background Mobile genetic elements (MGEs) are widely involved in the dissemination of antibiotic resistance genes and some of them, such as the integrative and conjugative element SXT, are even induced by specific antibiotics at sub-lethal concentrations. Objectives This work explores collateral effects of a broad range of antibiotics on the mobility of the SXTMO10 element using a specifically designed high-throughput screening test. Methods Twenty-five promoters involved in the mobility of SXT and six artificial constitutive promoters were transcriptionally fused to luxCDABE bioluminescent genes and introduced into Escherichia coli strains with or without SXT to build whole-cell biosensors for a large-scale screening involving 48 antibiotics. A bioluminescent assay implementing a classical agar diffusion approach was coupled to an automated data processing pipeline developed to extract and analyse luminescence data from over 2000 antibiotic/biosensor combination profiles. Results In addition to quinolones previously reported as inducing the expression of SXT mobility genes, we found that specific antibiotics belonging to other classes, such as imipenem and azithromycin, also behave as inducers. The use of a control set of constitutive biosensors also revealed an unexpected intricate relationship between cell respiration and light production that allowed the identification of antibiotics interfering with the respiration process. Conclusions The effect of antibiotics goes beyond the interaction with their primary cell targets and may lead to adverse effects such as triggering the dissemination of resistance by MGEs, sometimes in unpredictable ways. Identifying such MGE-triggering antibiotics is of prime importance for better controlling collateral effects during therapy

Changes in early intestinal microbiota induced by transfers of vaginal, milk-associated and fecal microbiota from pregnant mothers do not program intestinal microbiota in adult rats

International audienc

Changes in early intestinal microbiota induced by transfers of vaginal, milk-associated and fecal microbiota from pregnant mothers do not program intestinal microbiota in adult rats

International audienc