Biotechnical utilization of wood carbohydrates after steaming pretreatment

Summary Birch wood was used as raw material to study the effect of steaming pretreatment on the characteristics, enzymatic hydrolysis and fermentation of cellulose and hemicellulose. The cellulose remained undissolved in the fibres after steaming, but the degree of polymerization decreased and the surface area increased with increasing steaming temperature. The yield in enzymatic hydrolysis with T. reesei and A. niger cellulases increased from 40 to 75% of theoretical when the pretreatment temperature was increased from 170 to 210°C at a residence time of 10 minutes. The glucose released was fermented to ethanol by yeast without interference of toxic compounds. After steaming, the hemicellulose was mainly in the form of xylo-oligomers. The average chain length decreased with increasing temperature. Only the monomeric sugars were fermented to ethanol by Fusarium oxysporum. After steaming at 210°C toxic decomposition products inhibited the fermentation completely. In aerobic conditions also the xylo-oligomers were metabolized.     

Aetiology and pathogenesis of reactive arthritis: role of non-antigen-presenting effects of HLA-B27

Spondyloarthropathies are inflammatory diseases closely associated with human leukocyte antigen (HLA)-B27 by unknown mechanisms. One of these diseases is reactive arthritis (ReA), which is typically triggered by Gram-negative bacteria, which have lipopolysaccharide as an integral component of their outer membrane. Several findings in vivo and in vitro obtained from patients with ReA and from different model systems suggest that HLA-B27 modulates the interaction between ReA-triggering bacteria and immune cells by a mechanism unrelated to the antigen presentation function of HLA-B27. In this review we piece together a jigsaw puzzle from the new information obtained from the non-antigen-presenting effects of HLA-B27.     

Release of intact and fragmented osteocalcin molecules from bone matrix during bone resorption in vitro

Osteocalcin detected from serum samples is considered a specific marker of osteoblast activity and bone formation rate. However, osteocalcin embedded in bone matrix must also be released during bone resorption. To understand the contribution of each type of bone cell in circulating osteocalcin levels, we used immunoassays detecting different molecular forms of osteocalcin to monitor bone resorption in vitro. Osteoclasts were obtained from rat long bones and cultured on bovine bone slices using osteocalcin-depleted fetal bovine serum. In addition, human osteoclasts differentiated from peripheral blood mononuclear cells were used. Both rat and human osteoclasts released osteocalcin from bovine bone into medium. The amount of osteocalcin increased in the presence of parathyroid hormone, a stimulator of resorption, and decreased in the presence of bafilomycin A1, an inhibitor of resorption. The amount of osteocalcin in the medium correlated with a well characterized marker of bone resorption, the C-terminal telopeptide of type I collagen (r > 0.9, p < 0.0001). The heterogeneity of released osteocalcin was determined using reverse phase high performance liquid chromatography, and several molecular forms of osteocalcin, including intact molecule, were identified in the culture medium. In conclusion, osteocalcin is released from the bone matrix during bone resorption as intact molecules and fragments. In addition to the conventional use as a marker of bone formation, osteocalcin can be used as a marker of bone resorption in vitro. Furthermore, bone matrix-derived osteocalcin may contribute to circulating osteocalcin levels, suggesting that serum osteocalcin should be considered as a marker of bone turnover rather than bone formation.     

Birch PR-10c interacts with several biologically important ligands

PR-10c is a unique member of PR-10 proteins in birch, since it is the only one known to be post-translationally modified by glutathione and is not constitutively expressed in pollen. Both reduced and S-glutathiolated forms of PR-10c show low ribonuclease activity. However, the major function of the protein is apparently not yet resolved. Our protein-ligand interaction studies with saturation transfer difference (STD) NMR revealed that PR-10c interacts with several biologically important molecules, including cytokinin, flavonoid glycosides, sterols and emodin. Competition study with deoxycholate and kinetin revealed no statistically significant binding interference, indicating that these ligands have different binding sites in PR-10c. Ligand docking studies with a molecular model of PR-10c support the STD NMR results of ligand binding and binding epitopes, suggesting that there are three potential binding sites in PR-10c: two in the hydrophobic cavity and one in the glycine-rich loop. Our docking calculations suggested that only kinetin interacts with the glycine-rich loop, the binding occurring through its adenine moiety. Clear ligand specificity could be observed in the binding of nucleotide derivatives. S-glutathiolation of PR-10c did not affect kinetin binding. The present results suggest that birch PR-10c is a multifunctional protein, which has diverse roles in plant stress responses.     

Comparison of Pseudomonas fragi and Gluconobacter oxydans for production of xylonic acid from hemicellulose hydrolyzates

Summary Xylonic acid was produced efficiently from pure xylose by Pseudomonas fragi ATCC 4973 and Gluconobacter oxydans subsp. suboxydans ATCC 621. The yield from 10% xylose was in both cases over 95% of the theoretical. However, the sensitivities of the strains towards the major inhibitors found in hemicellulose hydrolyzates, ie. acetic acid, furfural and two lignin-derived compounds, varied. G. oxydans tolerated all these inhibitors better than P. fragi. In tests using steamed hemicellulose hydrolyzate, G. oxydans was able to utilize the substrate only at dilute xylose concentrations. After ether extraction or mixed bed resin pretreatment, the fermentability of the hydrolyzate was increased significantly.     

Design and evaluation of xanthine based adenosine receptor antagonists: Potential hypoxia targeted immunotherapies

Molecular modeling techniques were applied to the design, synthesis and optimization of a new series of xanthine based adenosine A_2A receptor antagonists. The optimized lead compound was converted to a PEG derivative and a functional in vitro bioassay used to confirm efficacy. Additionally, the PEGylated version showed enhanced aqueous solubility and was inert to photoisomerization, a known limitation of existing antagonists of this class.     

metaxa2: improved identification and taxonomic classification of small and large subunit rRNA in metagenomic data

The ribosomal rRNA genes are widely used as genetic markers for taxonomic identification of microbes. Particularly the small subunit (SSU; 16S/18S) rRNA gene is frequently used for species‐ or genus‐level identification, but also the large subunit (LSU; 23S/28S) rRNA gene is employed in taxonomic assignment. The metaxa software tool is a popular utility for extracting partial rRNA sequences from large sequencing data sets and assigning them to an archaeal, bacterial, nuclear eukaryote, mitochondrial or chloroplast origin. This study describes a comprehensive update to metaxa – metaxa 2 – that extends the capabilities of the tool, introducing support for the LSU rRNA gene, a greatly improved classifier allowing classification down to genus or species level, as well as enhanced support for short‐read (100 bp) and paired‐end sequences, among other changes. The performance of metaxa 2 was compared to other commonly used taxonomic classifiers, showing that metaxa 2 often outperforms previous methods in terms of making correct predictions while maintaining a low misclassification rate. metaxa 2 is freely available from http://microbiology.se/software/metaxa2/ .     

Europe's darker atmosphere in the UV-B

Irradiation in the ultraviolet wavelength range is found to be up to 50% lower in the European summer compared to sites with comparable latitudes in New Zealand. We have developed a method to quantitatively attribute the causes for such differences between sites by analysis of spectra. We conclude that these large differences are caused mainly by differences in total ozone, cloudiness, aerosol loading and Sun-Earth separation. The relative contribution of clouds varies from year to year and it is site dependent. Averaged over several years we find a strong latitudinal gradient of the cloud impact within Europe, with much less cloud attenuation in southern Europe. Due to the differences in total ozone and aerosol loading, the UV-B levels are generally lower in Europe compared to New Zealand. It is likely that inter-hemispheric differences will change in coming decades due to a combination of changes in ozone concentrations, air pollution and cloudiness as a result of climate change. However, since the future evolution of these major parameters is highly uncertain, the magnitude and even the sign of such changes are not known yet.     

The hydrolysis of steamed birchwood hemicellulose by enzymes produced byTrichoderma reesei andAspergillus awamori

Summary The hemicellulase separated from birchwood by steaming and water extraction comprised mainly of acetyl- and 4-O-methyglucurono-substituted xylo-oligomers. The liberation of the acidic side groups affected the rate and yield of the enzymatic hydrolysis of the xylo-oligomers. The hemicellulase ofTrichoderma reesei was superior to that ofAspergillus awamori both with respect to side group cleavage and xylose yield in hydrolysis.