Engineering Escherichia coli for succinate production from hemicellulose via consolidated bioprocessing

<p>Abstract</p> <p>Background</p> <p>The recalcitrant nature of hemicellulosic materials and the high cost in depolymerization are the primary obstacles preventing the use of xylan as feedstock for fuel and chemical production. Consolidated bioprocessing, incorporating enzyme-generating, biomass-degrading and bioproduct-producing capabilities into a single microorganism, could potentially avoid the cost of the dedicated enzyme generation in the process of xylan utilization. In this study, we engineered <it>Escherichia coli </it>strains capable of exporting three hemicellulases to the broth for the succinate production directly from beechwood xylan.</p> <p>Results</p> <p>Xylanases were extracellular environment-directed by fusing with OsmY. Subsequently, twelve variant OsmY fused endoxylanase-xylosidase combinations were characterized and tested. The combination of XynC-A from <it>Fibrobacter succinogenes </it>S85 and XyloA from <it>Fusarium graminearum </it>which appeared to have optimal enzymatic properties was identified as the best choice for xylan hydrolysis (0.18 ± 0.01 g/l protein in the broth with endoxylanase activity of 12.14 ± 0.34 U/mg protein and xylosidase activity of 92 ± 3 mU/mg protein at 8 h after induction). Further improvements of hemicellulases secretion were investigated by <it>lpp </it>deletion, <it>dsbA </it>overexpression and expression level optimization. With co-expression of α-arabinofuranosidase, the engineered <it>E. coli </it>could hydrolyze beechwood xylan to pentose monosaccharides. The hemicellulolytic capacity was further integrated with a succinate-producing strain to demonstrate the production of succinate directly from xylan without externally supplied hydrolases and any other organic nutrient. The resulting <it>E. coli </it>Z6373 was able to produce 0.37 g/g succinate from xylan anaerobically equivalent to 76% of that from xylan acid hydrolysates.</p> <p>Conclusions</p> <p>This report represents a promising step towards the goal of hemicellulosic chemical production. This engineered <it>E. coli </it>expressing and secreting three hemicellulases demonstrated a considerable succinate production on the released monosaccharides from xylan. The ability to use lower-cost crude feedstock will make biological succinate production more economically attractive.</p

The theory analysis and design for large parameter weak signal detector based on bistable stochastic resonance

Volume 3 Issue 11 (November 2015

Characterization, dissolution and solubility of the hydroxypyromorphite–hydroxyapatite solid solution [(PbxCa1−x)5(PO4)3OH] at 25 °C and pH 2–9

Additional file 1: Appendix A. Supplementary data—X-ray diffractograms (XRD) of the hydroxypyromorphite–hydroxyapatite solid solution [(PbxCa1−x)5(PO4)3(OH)] after dissolution at 25 ˚C and an initial pH of 5.60 and 9.00 for 300d

Molecular Basis of PIP2-dependent Conformational Switching of Phosphorylated CD44 in binding FERM

Association of the cellular adhesive protein CD44 and the N-terminal (FERM) domain of cytoskeleton adaptors is critical for cell proliferation, migration and signaling. Phosphorylation of the cytoplasmic domain (CTD) of CD44 acts as an important regulator of the protein association, but the structural transformation and dynamics mechanism remain enigmatic. In this study, extensive coarse-grained simulations were employed to explore the molecular details in the formation of CD44-FERM complex under S291 and S325 phosphorylation, a modification path known to exert reciprocal effects on the protein association. We find that phosphorylation of S291 inhibits complexation by causing the CTD of CD44 to adopt a more closed structure. In contrast, S325 phosphorylation liberates the CD44-CTD from the membrane surface and promotes the linkage with FERM. The phosphorylation-driven transformation is found to occur in a PIP2-dependent manner, with PIP2 effecting the relative stability of the closed and open conformation, and a replacement of PIP2 by POPS greatly abrogates this effect. The revealed interdependent regulation mechanism by phosphorylation and PIP2 in the association of CD44 and FERM further strengthens our understanding of the molecular basis of cellular signaling and migration.</p

The genome sequence of the orchid Phalaenopsis equestris

Orchidaceae, renowned for its spectacular flowers and other reproductive and ecological adaptations, is one of the most diverse plant families. Here we present the genome sequence of the tropical epiphytic orchid Phalaenopsis equestris, a frequently used parent species for orchid breeding. P. equestris is the first plant with crassulacean acid metabolism (CAM) for which the genome has been sequenced. Our assembled genome contains 29,431 predicted protein-coding genes. We find that contigs likely to be underassembled, owing to heterozygosity, are enriched for genes that might be involved in self-incompatibility pathways. We find evidence for an orchid-specific paleopolyploidy event that preceded the radiation of most orchid clades, and our results suggest that gene duplication might have contributed to the evolution of CAM photosynthesis in P. equestris. Finally, we find expanded and diversified families of MADS-box C/D-class, B-class AP3 and AGL6-class genes, which might contribute to the highly specialized morphology of orchid flowers. (Résumé d'auteur

ERP Perspective Analysis of PSS Component and Decision-Making

This paper has developed a neuromarketing framework measuring the relationship between products and services in product&#8315;service systems (PSSs), particularly regarding its impact on PSS decision making. We divided the PSSs into different levels of product and service combinations in order to identify the impact of the various elements in PSS on decision making, particularly the key factor that induces significant variation in the purchase rate. The experiments showed the neural mechanisms behind the value perception of PSSs; this has been indicated by the appearance of N170, which is related to the cognition processing of familiarity and similarity. It is concluded that the perceived value of the product-oriented PSS is mainly determined by the product attribute, as the promotional effect of service has been clarified. The results explain the psychological and neurological activities that take place when consumers are browsing product&#8315;service bundles, which may help corporations better understand the relationships among the components in product&#8315;service bundles, providing insight for PSS innovation and service design

THIN SEAM SHEARER RELIABILITY ANALYSIS UNDER COMPLEX COAL SEAM OCCURRENCE CONDITIONS

Based on the rigid-flexible coupling multi-body system dynamics theory,built the rigid-flexible coupling model of shearer’s cutting part,researched the annular gear dynamic behavior during the process of meshing. According to the resistance of coal mining machine drum in the complex coal seam condition,generated the text files of the drum load based on Matlab programming. Simulated the model by Recur Dyn multi-body dynamics software,obtained the stress distribution of the shearer annular gear and contact force and contact moment with planetary gear,verified its correctness compared with the theoretical value. Through the fatigue life calculation,obtained the minimum fatigue cycles of annular gear tooth surface. Put forward improvement methods on the weak area and prolong its service life. Analyze its reliability when design could decrease the cost of research,provides a new method for the study of stress and fatigue life of shearer’s equipment in a wide range of rigid motion and small deformation of flexible component motion