Enzymatic hydrolosis of isolated and fibre-bound galactoglucomannans from pine-wood and pine kraft pulp

Fibre-bound and isolated galactoglumanans from pine-wood and pine kraft pulp were hydrolysed with purified mannanases from Trichoderma reesei and Bacillus subtilis. The isolated galactoglucomannans from both wood and pulp could be hydrolysed fairly extensively with both enzymes. In addition to mixed oligomers, the fungal mannase produced mannobiose as the main hydrolysis product whereas the bacterial mannanase produced mannobiose, mannotriose and mannotetraose. Both enzymes hydrolysed the native galactoglucomannan in finely ground pinewood, whereas galactoglucomannan in pine kraft pulp was only hydrolysed by the T. ressei mannanase. Thus, mannanases exhibit different specificities on fibre-bound, modified substrates. In spite of the high enzyme loading, the degree of hydrolysis of fibre-bound substrates did not exceed 10% of the theoretical, probably due to poor accessibility of the substrates. Correspondence to: M. Rättö     

Simulation of phototaxis in the flagellateEuglena gracilis

A three-dimensional model of the flagellateEuglena gracilis was developed to simulate phototaxis and movement in space. The simulation of the phototactic behavior was compared with thein vivo behavior in order to determine the mechanism of orientation with respect to light. Phototactic behavior with respect to one light source, can be explained by the shading hypothesis as well as by a dichroic orientation of the absorbing vectors of the photoreceptor pigments. In contrast, the behavior of the cells when exposed to two perpendicular light beams is not compatible with the shading hypothesis. Likewise, the phototactic orientation of stigmaless cells cannot be accounted for on the basis of the shading hypothesis. In contrast, simulations andin vivo observations of the behavior under polarized light strongly indicate the validity of the dichroic orientation of the photoreceptor pigments.     

Nutrient-split feeding strategy for dialysis cultivation of Escherichia coli

Reduction in nutrient loss during dialysis cultivation of Escherichia coli on a glycerol medium was investigated. A dialysis reactor with an inner fermentation and an outer dialysis chamber was used. Aerobic condition was maintained by limiting the glycerol feed rate to an optimum value which was estimated from the oxygen requirements for glycerol oxidation and oxygen transfer capacity of the reactor. High reduction in nutrient loss was achieved by using water as the dialyzing fluid. However, osmotic movement of water from the dialysis to the fermentation chamber was observed, and the final cell concentration was low. With a nutrient-split feeding strategy (feeding glycerol directly to the fermentation chamber and dialyzing with salt solution), glycerol loss was small, there was no osmotic flux of water to the fermentation chamber, and the cell concentration was high. Both glycerol and salt loss could be avoided, and a cell concentration of 170 g/L was obtained when the dialysis process was substituted by addition of XAD adsorbents to the dialysis chamber. Application of this nutrient-split feeding strategy to cell cultivation in a stirred tank reactor, coupled with dialysis in external dialyzer modules, resulted in low cell concentrations. (c) 1993 Wiley & Sons, Inc.     

Ribosomal RNA genes in Scots pine (Pinus sylvestris L.): Chromosomal organization and structure

The nuclear 18S, 5.8S and 25S rRNA genes exist as thousands of rDNA repeats in the Scots pine genome. The number and location of rDNA loci (nucleolus organizers, NORs) were studied by cytological methods, and a restriction map from the coding region of the Scots pine rDNA repeat was constructed using digoxigenin-labeled flax rDNA as a probe. Based on the maximum number of nucleoli and chromosomal secondary constrictions, Scots pine has at least eight NORs in its haploid genome. The size of the Scots pine rDNA repeat unit is approximately 27 kb, two- or threefold larger than the typical angiosperm rDNA unit, but similar in size to other characterized conifer rDNA repeats. The intergenic spacer region (IGS) of the rDNA repeat unit in Scots pine is longer than 20 kb, and the transcribed spacer regions surrounding the 5.8S gene (ITS1 and ITS2) span a region of 2.9 kb. Restriction analysis revealed that although the coding regions of rDNA repeats are homogeneous, heterogeneity exists in the intergenic spacer region between individuals, as well as among the rDNA repeats within individuals.     

Genetic mapping of the erythropoietin receptor gene

We describe a novel, highly informative (polymorphism information content, PIC, = 0.86) simple sequence repeat polymorphism at the 5 end of the gene encoding the human erythropoietin receptor (EPOR) previously assigned to 19pl3.2 by in situ hybridization. Fourteen different allelic size variants were identified in 12 families of the CEPH (Centre d'Etude du Polymorphisme Humain) family panel of 40 families. In pairwise linkage 16 of the 65 chromosome 19 markers reported to the CEPH database gave a lod score exceeding 3.0 when tested against EPOR. The most likely location of EPOR within a framework of 10 markers including orientation and information on reported physical assignments was pter-[INSR-D1 9S177-D19S176]-D 19S24-LDLR-EPOR-cen-D-19S7-D19S49-D19S75-D19S47-APOC2-qter, placing EPOR as the most proximal of the tested loci on the short arm. On an 11-point map the position and order for all other loci except INSR were supported by the data with odds exceeding 1,000:1. The polymorphism at the 5 end of EPOR should provide a useful landmark marker for future mapping studies of this region.     

Rate Equations and Product Yields of Serine Proteinase Catalysed Transfer Reactions

The steady state rate equations of transfer reactions catalysed by enzymes that follow the serine proteinase reaction mechanism in their hydrolysis reactions, have been solved and integrated. The integrated equations allow for calculations of maximal yields of product and of the time, t_max, at which that yield is present in a given reaction mixture. These important quantities have not been dealt with in previous theoretical studies of such systems.     

A Simple and Safe Device for Spreading Ultrathin Sections with Chloroform

A simple and safe device for spreading ultrathin sections for electron microscopy is described. The use of this device minimizes the release of chloroform vapor during section spreading.     

Neutral gravitaxis of gliding Loxodes exposed to normal and raised gravity

Summary In the statocystoid-bearing, flat ciliate Loxodes, the peculiar steady locomotion on submersed substrates (called gliding) was investigated between 1 g and 5.4 g under controlled environmental conditions in a centrifuge microscope. Videorecordings of the movements of large cell populations were processed with an automated analysis procedure. At 1 g, possible sedimentation was fully compensated, and vertical shifts of the population were neutralized because upward and downward orientations of the cells occurred at equal proportions (neutral gravitaxis). With rising gravity the resultant velocity of upward-gliding cells remained unchanged, whereas the velocity of downward-gliding cells increased continuously. Long-term exposure to hypergravity did not generate detectable signs of adaptation. The bipolar orientation of Loxodes persisted even under fivefold normal gravity, but the axis of orientation rotated from the gravity axis in the counterclockwise direction. The data suggest that both gravikinesis and graviorientation of gliding Loxodes are instrumental in perfect neutralization of sedimentation at terrestrial conditions.     

Systematics ofPrimula veris (Primulaceae)

Primarily, 50 characters taken from herbarium specimens, cultivated plants, and whole populations ofPrimula veris L. were critically evaluated. Only 24 characters were found to be suitable for taxonomic use. The geographical and multivariate analysis of about 1000 herbarium specimens from the whole area lead to a reduction of the number of subspecies. Only a less restricted subsp.veris (incl. subsp.canescens, subsp.inflata and probably including subsp.macrocalyx) and subsp.columnae (incl. subsp.suaveolens) can be distinguished considering the variability of characters within an individuum, under different culture conditions, and during the growth period. The status of the taxon macrocalyx cannot be cleared presently.