Dissolved Organic Carbon in the North Atlantic Meridional Overturning Circulation

The quantitative role of the Atlantic Meridional Overturning Circulation (AMOC) in dissolved organic carbon (DOC) export is evaluated by combining DOC measurements with observed water mass transports. In the eastern subpolar North Atlantic, both upper and lower limbs of the AMOC transport high-DOC waters. Deep water formation that connects the two limbs of the AMOC results in a high downward export of non-refractory DOC (197 Tg-C·yr-1). Subsequent remineralization in the lower limb of the AMOC, between subpolar and subtropical latitudes, consumes 72% of the DOC exported by the whole Atlantic Ocean. The contribution of DOC to the carbon sequestration in the North Atlantic Ocean (62 Tg-C·yr-1) is considerable and represents almost a third of the atmospheric CO 2 uptake in the region

Kongressforum Holz im Rahmen der Internationalen Gruenen Woche in Berlin 1994

Includes 29 articlesAvailable from Bibliothek des Instituts fuer Weltwirtschaft, ZBW, Duesternbrook Weg 120, D-24105 Kiel C 189476 / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekSIGLEDEGerman

Konzeptstudie fuer die energetische Nutzung von Abfaellen in Niedersachsen

SIGLEAvailable from Institut fuer Angewandte Systemforschung und Prognose (ISP), Hannover (DE) / FIZ - Fachinformationszzentrum Karlsruhe / TIB - Technische InformationsbibliothekDEGerman

The hemicellulose-degrading enzyme system of the thermophilic bacterium Clostridium stercorarium: comparative characterisation and addition of new hemicellulolytic glycoside hydrolases

Background: The bioconversion of lignocellulosic biomass in various industrial processes, such as the production of biofuels, requires the degradation of hemicellulose. Clostridium stercorarium is a thermophilic bacterium, well known for its outstanding hemicellulose-degrading capability. Its genome comprises about 50 genes for partially still uncharacterised thermostable hemicellulolytic enzymes. These are promising candidates for industrial applications. Results: To reveal the hemicellulose-degrading potential of 50 glycoside hydrolases, they were recombinantly produced and characterised. 46 of them were identified in the secretome of C. stercorarium cultivated on cellobiose. Xylanases Xyn11A, Xyn10B, Xyn10C, and cellulase Cel9Z were among the most abundant proteins. The secretome of C. stercorarium was active on xylan, beta-glucan, xyloglucan, galactan, and glucomannan. In addition, the recombinant enzymes hydrolysed arabinan, mannan, and galactomannan. 20 enzymes are newly described, degrading xylan, galactan, arabinan, mannan, and aryl-glycosides of beta-D-xylose, beta-D-glucose, beta-D-galactose, alpha-L-arabinofuranose, alpha-L-rhamnose, beta-D-glucuronic acid, and N-acetyl-beta-D-glucosamine. The activities of three enzymes with non-classified glycoside hydrolase (GH) family modules were determined. Xylanase Xyn105F and beta-D-xylosidase Bxl31D showed activities not described so far for their GH families. 11 of the 13 polysaccharide-degrading enzymes were most active at pH 5.0 to pH 6.5 and at temperatures of 57-76 degrees C. Investigation of the substrate and product specificity of arabinoxylan-degrading enzymes revealed that only the GH10 xylanases were able to degrade arabinoxylooligosaccharides. While Xyn10C was inhibited by alpha-(1,2)-arabinosylations, Xyn10D showed a degradation pattern different to Xyn10B and Xyn10C. Xyn11A released longer degradation products than Xyn10B. Both tested arabinose-releasing enzymes, Arf51B and Axh43A, were able to hydrolyse single-as well as double-arabinosylated xylooligosaccharides. Conclusions: The obtained results lead to a better understanding of the hemicellulose-degrading capacity of C. stercorarium and its involved enzyme systems. Despite similar average activities measured by depolymerisation tests, a closer look revealed distinctive differences in the activities and specificities within an enzyme class. This may lead to synergistic effects and influence the enzyme choice for biotechnological applications. The newly characterised glycoside hydrolases can now serve as components of an enzyme platform for industrial applications in order to reconstitute synthetic enzyme systems for complete and optimised degradation of defined polysaccharides and hemicellulose

An essential serotype recognition pocket on phage P22 tailspike protein forces Salmonella enterica serovar Paratyphi A O antigen fragments to bind as nonsolution conformers

Bacteriophage P22 recognizes O-antigen polysaccharides of Salmonella enterica subsp. enterica (S.) with its tailspike protein (TSP). In the serovars S. Typhimurium, S. Enteritidis, and S. Paratyphi A, the tetrasaccharide repeat units of the respective O-antigens consist of an identical main chain trisaccharide but different 3,6-dideoxyhexose substituents. Here, the epimers abequose, tyvelose, and paratose determine the specific serotype. P22TSP recognizes O-antigen octasaccharides in an extended binding site with a single 3,6-dideoxyhexose binding pocket. We have isolated S. Paratyphi A octasaccharides which were not available previously and determined the crystal structure of their complex with P22TSP. We discuss our data together with crystal structures of complexes with S. Typhimurium and S. Enteritidis octasaccharides determined earlier. Isothermal titration calorimetry (ITC) showed that S. Paratyphi A octasaccharide binds P22TSP less tightly, with a difference in binding free energy of approximately 7 kJ/mol at 20 degrees C compared to S. Typhimurium and S. Enteritidis octasaccharides. Individual protein-carbohydrate contacts were probed by amino acid replacements showing that the dideoxyhexose pocket contributes to binding of all three serotypes. However, S. Paratyphi A octasaccharides bind in a conformation with an energetically unfavorable varphi / psi glycosidic bond angle combination. By contrast, octasaccharides from the other serotypes bind as solution-like conformers. Two water molecules are conserved in all P22TSP complexes with octasaccharides of different serotypes. They line the dideoxyhexose binding pocket and force the S. Paratyphi A octasaccharides to bind as non-solution conformers. This emphasizes the role of solvent as part of carbohydrate binding sites