Lignocelluloses complexity

Corn stover, like lignocellulosic materials in general, is resistant to enzymatic hydrolysis, because of both the tight network in the lignocellulose complex and the crystalline structure of the native cellulose. These difficulties can be overcome by employing a suitable pretreatment (7). 

The breakdown of the swollen fiber cell wall is a process that proceeds from cell layer to cell layer. Apparently the carbohydrates in one cell must be almost totally dissolved before the next cell is attacked. Individual cells or small clusters of cells may remain relatively intact for some time behind the degradation front. This phenomenon could result from small differences in the degree of lignification, packing density of the lignocellulose complex, and content of extractives incrusting the cell wall. 

In deciduous species, swelling of secondary cell walls loosens the ultrastructure of the lignocellulose complex, and hydrolysis of hemicelluloses begins. This process seems either to spread quite rapidly or to occur about simultaneously throughout the piece of wood. In spruce, no swelling was observed. 

Cellulose is closely related to other biopolymers foimd in wood and plants. Together, these compounds are the raw materials used in a number of products encountered in forensic chemistry. For example, paper is made from wood chips derived from soft or hard woods, plants, or recycled paper stocks. Of interest in paper production are the polysaccharides found in wood— lignin, hemicellu-lose, and cellulose, all classified as part of the lignocellulose complex found in biomass such as wood. The lignocellulose compounds impart strength and... 

The macerals in lower rank coals, eg, lignite and subbiturninous coal, are more complex and have been given a special classification. The term huminite has been appUed to the macerals derived from the humification of lignocellulosic tissues. Huminite is the precursor to the vitrinite observed in... 

This conclusion is based on a high char yield and similar rates of mass loss at 300°C for untreated and boric acid treated samples. Boric acid samples also had much higher AH+ s and, consequently, higher Ea s. Our results suggest that certain thermally-stable, weak polybasic acids which can complex with polysaccharides may provide fire-resistant properties to lignocellulosics. The results and conclusions were strongly influenced by the technique used to analyze the TGA data. 

Various solvents are being investigated to dissolve lignocellulosic materials. Some approaches focus on the selective depolymerization and extraction of lignin and hemicellulose as pre-treatment to produce clean cellulose fibers for subsequent fermentation or for pulping. Other approaches attempt to dissolve the whole lignocellulose with or without depolymerization. The liquefaction processes that are carried out at high temperature (>300 °C), and produce a complex oil mixture, are discussed above with the pyrolysis processes. 

T. harzianum IMI 275950 isolated from wheat straw grew better on lignocellulose (Table I). Despite these differences, the enzyme yields of the cellulase/xylanase complexes did not correlate with growth rate. These observations from this empirical study indicate that strains isolated or derived for growth on extracted substances may not necessarily be the most useful strains to exploit natural substrates. 

Synthetic medium containing xylose or arabinose and one or more complex ingredients (unless otherwise indicated). b Mixed sugar hydrolysate of native lignocellulosic substrate lacking complex medium ingredients. Detoxification applied unless otherwise indicated. 

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