Biorefining of wood: combined production of ethanol and xylanase from waste fiber sludge

The possibility to utilize fiber sludge, waste fibers from pulp mills and lignocellulose-based biorefineries, for combined production of liquid biofuel and biocatalysts was investigated. Without pretreatment, fiber sludge was hydrolyzed enzymatically to monosaccharides, mainly glucose and xylose. In the first of two sequential fermentation steps, the fiber sludge hydrolysate was fermented to cellulosic ethanol with the yeast Saccharomyces cerevisiae. Although the final ethanol yields were similar, the ethanol productivity after 9.5?h was 3.3?g/l/h for the fiber sludge hydrolysate compared with only 2.2?g/l/h for a reference fermentation with similar sugar content. In the second fermentation step, the spent fiber sludge hydrolysate (the stillage obtained after distillation) was used as growth medium for recombinant Aspergillus niger expressing the xylanase-encoding Trichoderma reesei (Hypocrea jecorina) xyn2 gene. The xylanase activity obtained with the spent fiber sludge hydrolysate (8,500?nkat/ml) was higher than that obtained in a standard medium with similar monosaccharide content (1,400?nkat/ml). Analyses based on deglycosylation with N-glycosidase?F suggest that the main part of the recombinant xylanase was unglycosylated and had molecular mass of 20.7?kDa, while a minor part had N-linked glycosylation and molecular mass of 23.6?kDa. Chemical analyses of the growth medium showed that important carbon sources in the spent fiber sludge hydrolysate included xylose, small aliphatic acids, and oligosaccharides. The results show the potential of converting waste fiber sludge to liquid biofuel and enzymes as coproducts in lignocellulose-based biorefineries.     

Juniper fields in Sogn, Western Norway, a man-made vegetation type

Juniperus communis has been used e.g. as poles (posts), haysticks and wall-coating. In some districts it has even been an important export article. The fields of columnar juniper are the result of a long history of cultivation and grazing. In this article the main types of juniper fields in Sogn, Western Norway are presented, and their relationships to soil conditions and traditional use are discussed. According to structure, utilization and development four main types of juniper fields are recognized: I. Traditional juniper fields, II. Semi-cultural juniper fields, III. Secondary juniper fields and IV. Semi-natural juniper fields. Due to changes in agricultural methods, juniper fields are becoming rare.     

Acute Effect of Ammonia on Branched-Chain Amino Acid Oxidation and Incorporation into Proteins in Astrocytes and in Neurons in Primary Cultures

14CO2 production and incorporation of label into proteins from the labeled branched-chain amino acids, leucine, valine, and isoleucine, were determined in primary cultures of neurons and of undifferentiated and differentiated astrocytes from mouse cerebral cortex in the absence and presence of 3 mM ammonium chloride. Production of 14CO2 from [1-14C]leucine and [1-14C]valine was larger than 14CO2 production from [U-14C]leucine and [U-14C]valine in both astrocytes and neurons. In most cases more 14CO2 was produced in astrocytes than in neurons. Incorporation of labeled branched-chain amino acids into proteins varied with the cell type and with the amino acid. Addition of 3 mM ammonium chloride greatly suppressed 14CO2 production from [1-14C]-labeled branched chain amino acids but had little effect on 14CO2 production from [U-14C]-labeled branched-chain amino acids in astrocytes. Ammonium ion, at this concentration, suppressed the incorporation of label from all three branched-chain amino acids into proteins of astrocytes. In contrast, ammonium ion had very little effect on the metabolism (oxidation and incorporation into proteins) of these amino acids in neurons. The possible implications of these findings are discussed, especially regarding whether they signify variations in metabolic fluxes and/or in magnitudes of precursor pools.     

Similarities of adenosine uptake systems in astrocytes and neurons in primary cultures

Uptake of extracellular adenosine was studied in primary cultures of astrocytes or neurons. Both cell types showed a high affinity uptake. TheK _m values were not significantly different (6.5±3.75 M in astrocytes and 6.1±1.86 M in neurons), but the intensity of the uptake was higher in astrocytes than in neurons (V _max values of 0.16±0.030 and 0.105±0.010 nmol×min^–1×mg^–1 protein, respectively). The temperature sensitivity was similar in the two cell types. Adenosine uptake inhibitors and benzodiazepines inhibited the adenosine uptake systems in both astrocytes and neurons with IC₅₀ values in the high nanomolar or the micromolar range and the rank order of potency was similar in the two cell types. In both cell types the (–) isomers of two sets of benzodiazepine stereoisomers were more potent than the (+) isomers. Dixon analysis showed that dipyridamole, papaverine, hexobendine and chlordiazepoxide inhibited the adenosine uptake competitively and clonazepam noncompetitively in both cell types.     

Functional interactions in vivo between suppressor tRNA and mutationally altered ribosomal protein S4

Summary Ribosomal mutants (rpsD) which are associated with a generally increased translational ambiguity were investigated for their effects in vivo on individual tRNA species using suppressor tRNAs as models. It was found that nonsense suppression is either increased, unaffected or decreased depending on the codon context and the rpsD allele involved as well as the nature of the suppressor tRNA. Missense suppression of AGA and AGG by glyT(SuAGA/G) tRNA as well as UGG by glyT(SuUGG-8) tRNA is unaffected whereas suppression of UGG by glyT(SuUGA/G) or glyV(SuUGA/G) tRNA is decreased in the presence of an rpsD mutation. The effects on suppressor tRNA are thus not correlated with the ribosomal ambiguity (Ram) phenotype of the rpsD mutants used in this study. It is suggested that the mutationally altered ribosomes are changed in functional interactions with the suppressor tRNA itself rather than with the competing translational release factor(s) or cognate aminoacyl tRNA. The structure of suppressor tRNA, particularly the anticodon loop, and the suppressed codon as well as the codon context determine the allele specific functional interactions with these ribosomal mutations.     

Differences in reactivity of confluent and nonconfluent cultures of human endothelial cells toward thrombin-stimulated platelets or heparinized salt solution

Summary This study examined whether nonconfluent endothelial cell cultures reacted differently than confluent ones toward thrombin-stimulated platelets or a heparinized salt solution. The adherence to the endothelial cell cultures of⁵¹Cr-labeled human platelets stimulated at different thrombin concentrations was studied. There was significantly higher adherence of stimulated platelets to nonconfluent cultures compared with confluent ones. This was confirmed by scanning electron microscopy, which also revealed a tendency for the platelets to adhere at the cell periphery. Electron microscopy also showed that thrombin-stimulated platelets induced endothelial cell contraction. Part of the peripheral endothelial cell surface toward the bottom of the culture dish was inverted, facing the lumen of the dish. This phenomenon was particularly seen in nonconfluent cultures. When⁵¹Cr-labeled endothelial cultures were incubated with a mildly injurious fluid as heparinized sodium acetate and 20% serum, at 20° C for 30 min, the nonconfluent cultures showed significantly more cell detachment and release of⁵¹Cr than the confluent ones. We conclude that under the conditions of the present experiments there are differences in the reactivity of confluent and nonconfluent endothelial cell cultures. These differences probably reflect biological dissimilarities. In experiments where properties of cultured endothelium are studied, care should be taken that the degree of confluency is standardized.     

Two-dimensional impedance studies of BSA buoyant density separated human erythrocytes

Combined DC (Coulter Volume) and radio frequency impedance studies were performed on human erythrocytes which had been separated by buoyant density in linear, neutral, isotonic bovine serum albumin gradients. The individual buoyant density fractions showed no reproducible shift in volume with buoyant density but did show a shift with opacity, radio frequency impedance divided by dc impedance. This new electronic parameter of opacity can be related to cell age, since both it and cell age are directly related to buoyant density. This increase in opacity with buoyant density is correlated with a change in shape.     

Resource partitioning of roach Rutilus rutilus and bleak Alburnus alburnus in two eutrophic lakes in SE Norway

In this paper I investigate the resource partitioning of roach Rutilus rutilus and bleak Alburnus alburnus in two eutrophic lakes in SE Norway. Zooplankton was the preferred food item for both species during summer, whereas blue-green algae dominated the diet in September/October. There was no diet overlap in May, with the roach feeding mainly on detritus and the bleak feeding on surface insects. During summer the diet overlap increased, reaching high values in autumn. Habitat overlap was close to unity in spring and early summer. Coinciding with increasing diet overlap during summer and autumn the overlap in habitat decreased.     

Linkage relationships in the bovine MHC region. High recombination frequency between class II subregions

Class II genes of the bovine major histocompatibility complex (MHC) have been investigated by Southern blot analysis using human DNA probes. Previous studies revealed the presence of bovine DO , DQ , DQ , DR and DR genes, and restriction fragment length polymorphisms for each of these genes were documented. In the present study, the presence of three additional class II genes, designated DZ , DY , and DY , are reported. DZ was assumed to correspond to the human DZ gene while the other two were designated DY because their relationship to human class II genes could not be firmly established. The linkage relationships among bovine class II genes and two additional loci, TCP1B and C4, were investigated by family segregation analysis and analysis of linkage disequilibrium. The results clearly indicated that all these loci belong to the same linkage group. This linkage group is divided into two subregions separated by a fairly high recombination frequency. One region includes the C4, DQ , DQ , DR and DR loci and the other one is composed of the DO DY , DY , and TCPIB loci. No recombinant was observed within any of these subregions and there was a strong or fairly strong linkage disequilibrium between loci within groups. In contrast, as many as five recombinants among three different families were detected in the interval between these subregions giving a recombination frequency estimate of 0.17 ± 0.07. The fairly high recombination frequency observed between class 11 genes in cattle is strikingly different from the corresponding recombination estimates in man and mouse. The finding implies either a much larger molecular distance between some of the bovine class II genes or alternatively the presence of a recombinational hot spot in the bovine class II region.