Structure and chemical composition of bast fibers isolated from developing hemp stem.

Microscopic and chemical changes of hemp bast fibers were studied during the maturation from vegetative to grain maturity stages at both apical and basal regions of the stems. The content of protein was the main factor related to fiber maturation, whereas increased proportions of mannose and glucose and decreasing levels of galactose were also highly significant. Enhanced glucose deposition in apical fibers could be related to the gradual thickening of the fibers, whereas in basal regions the thickness of the fibers nearly reached the maximum at vegetative stages.

Aggregation during coniferyl alcohol polymerization in pectin solution: a biomimetic approach of the first steps of lignification.

Coniferyl alcohol was polymerized in pectin solution in order to mimic the lignification that is the final step of biosynthesis of plant cell wall. Dehydrogenated polymers (DHP = coniferyl alcohol polymers = synthetic lignin) interact with pectin to form hydrophobic clusters as monitored by pyrene fluorescence spectroscopy. The structure of these clusters was studied during the polymerization of synthetic lignin by static and quasielastic light scattering and small angle neutron scattering experiments.

Association behaviour of lignins and lignin model compounds studied by multidetector size-exclusion chromatography.

SEC elution curves of spruce milled wood lignin (MWL) and guaiacyl lignin polymer models (G-DHPs) in N,N-dimethylformamide (DMF) exhibited a bimodal elution profile. Light scattering measurements indicated that these elution profiles were due to association effects between the molecules. This became apparent from the determination of high molar masses in the range 10(5)-10(8) g/mol.

Mechanical, chemical and X-ray analysis of wood in the two tropical lianas Bauhinia guianensis and Condylocarpon guianense: variations during ontogeny.

Mechanical and chemical properties as well as microfibril angles of wood tissues from different ontogenetic stages are determined for the neotropical lianas Bauhinia guianensis and Condylocarpon guianense. The mechanical properties include the elastic moduli under bending and under dynamic torsion. The chemical analyses cover (i) the content of cellulose, lignin and hemicelluloses fractions, (ii) the monomeric composition of the uncondensed lignin, and (iii) the composition of the hemicelluloses with respect to neutral monosaccharides.

Synthesis and characterization of dehydrogenation polymers in Gluconacetobacter xylinus cellulose and cellulose/pectin composite.

To mimic the lignin polymerization process, mats of bacterial cellulose and of a pectin/cellulose composite were used as a host matrix for in vitro polymerization of coniferyl alcohol. A diffusion cell was used to allow the diffusion of both hydrogen peroxide and coniferyl alcohol into the peroxidase impregnated cellulose mats through dialysis membranes. The results indicate that significant polymerization occurs within the mats.