Spruce, acidic hemicelluloses

From recent literature it is known that the disintegration of lignified cell walls can be achieved by steam explosion treatments resulting in solubilization of partially depolymerized hemicelluloses [91,92]. The application of this method on wheat bran yielded feruloylated GAX with different feruUc acid content [93]. Partly depolymerized water-soluble, acetylated AGX was obtained from spruce wood by employing microwave treatment [94]. 

Tritiated Water. Exchange with tritiated water and subsequent scintillation analysis of the tritium content is a very useful method for accessibility measurements when the samples are not transparent to IR and visible light. Thin shives of sapwood from black spruce (a common softwood), and white birch (a common hardwood) where studied before and after delignification by treatment with peracetic acid (17). Also wood cambium from the same softwood was studied. The cambium is the recently formed fiber layer, located close to the bark and not yet lignified. Spruce and birch wood contain about the same amounts of cellulose, 42 and 44%, respectively. Spruce wood has more lignin (28 vs. 18% ), while birch has more hemicellulose (35 vs. 2S% ), in particular more pentosans than spruce (24 vs. 14%). 

Acetic acid, formic acid and ievulinic acid are the most common carboxylic acids found in the hydrolyzates. Acetic acid is not only a by-product of hydrolysis (45) but is also a well-known by-product in fermentation (46). Acetic acid is mainly formed from acetylated sugars in the hemicellulose, which are cleaved off already at mild hydrolysis conditions. Therefore, die acetic acid yield in the hydrolysis does not significantly depend on the severity of the hydrolysis process (2). Hydrolysis of hardwoods (alder, aspen and birch) at 198-234°C, 0.5 g/1 H2SO4, and 33% wood dry materials for 7 min resulted in approximately 10 g/l acetic acid, whereas the hydrolysis of softwoods (pine and spruce) produced 3 g/1 acetic acid at similar conditions (2). 

PMOs are supposed to be active only on (semi)ctystalline polysaccharides and not on short soluble oligosaccharides (DP 2-5). Harris et al. tried a whole variety of substrates and concluded that mixed substrates like PCS (pre-treated corn stover) generate higher activities than pure cellulose substrates like Avicel (microcrystalline cellulose) or PASC (phosphoric acid swollen cellulose).However, hemicellulose substrates do not tend to be more efficiently degraded by PMO addition. The first successful experiments with real pre-treated biomass, namely pre-treated spruce, were recently performed. ... 

C12H22O11 342.299 Structural unit in the glucomannans of plant hemicelluloses. Isol. from the partial acid hydrolysates of the glucomannans from Amorphophallus spp., white spruce (Pinus glauca), western hemlock (Tsuga heterophylla), red maple (Acer rubrum), eastern white pine (Pinus strobus), larch (Larix decidua), jack pine (Pinus bank-siana) and from Narcissus tazetta from hemicelluloses of lobolly pine (Pinus taeda) and in trace amounts from the acetolysates of the a-celluloses from white birch (Betula papyrifera) and slash pine... 

C12H20O11 340.283 Isol. from partial acid hydrolysates of maritime pine Pinus pinaster), birch (Betula verrucosa) and Scandinavian spruce (Picea abies) hemicelluloses. 

Isol. from the partial acid hydrolysates of white spruce (Picea glauca), western hemlock (Tsuga heterophylla), jute fibre, maritime pine (Pinus pinaster), aspen (Populus tremuloides) hemicelluloses. 

Wood pulp (kraft pulp) from a mixture of spruce and pine was supplied from Sddra Cell Tofte, Norway. It is composed of eellulose and hemicellulose. The pulp was dissolved in trifluoroacetie acid (TEA) to a concentration of 1 wt%. The disso-... 

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