Hemicelluloses application

In the past, research activities in the field of hemicellulose were aimed mainly at utilizing plant biomass by conversion into sugars, chemicals, fuel and as sources of heat energy. However, hemicelluloses, due to their structural varieties and diversity are also attractive as biopolymers, which can be utilized in their native or modified forms in various areas, including food and non-food applications. 

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]. 

For thousands of years, nature has provided humankind with a large variety of materials for the most diversified applications for its survival, such as food, energy, medicinal products, protection and defense tools, and others. The pharmaceutical industry has benefitted from such diversity of biomaterials and has exploited the use of natural products as sources of both drugs and excipients. One example of a promising biomaterial for pharmaceutical use is xylan, a hemicellulose largely found in nature, being considered the second most abundant polysaccharide after cellulose. 

Ebringerova, A. (2005). Structural diversity and application potential of hemicelluloses. 

Abatzoglou, N. and Chornet, E. (1998) Acid hydrolysis of hemicellulose and cellulose. Theory and Applications, in Polysaccharides, Marcel Dekkes, New York, pp. 1007-1045. 

Further research is directed to the determination of the fine-structure of the pectins and hemicelluloses isolated from soy meal, using chromatography and degradation with specific enzymes. With these results a model of the polysaccharides present in the cell wall of soy will be formulated. Furthermore, application directed experiments will be performed to obtain information about structure-function relationships. 

The second area of application involves the use of cellulase-free xylanases for removal of hemicellulose from pulps (10-20) and plant fibres (21). It is essential that these xylanase preparations are free of contaminating cellulase activity or damage to the cellulose fibres and consequently the product quality will result. 

The pulps listed in Fig. 1 are characterized on an unbleached basis as produced by processes conventionally called pulping processes. In many instances, these pulps must be further treated chemically to remove residual lignin, hemicellulose, and color bodies before they can be considered suitable for use in specific applications. This further treatment is called bleaching, and the bleaching operation is actually an extension of the pulping process. 

In the present study, two mass transfer models were adapted from other applications, and preliminary comparisons were made to conventional reaction-only models to assess their abilities to describe hemicellulose hydrolysis inbatch and flowthrough reactors. Particular attention was paid to including production and diffusion of oligomers in these models with the intent of exploring whether this approach holds promise for explaining the performance of batch and flowthrough systems in a more consistent manner. 

Figures 1 and 2 present some representative results for the application of Eq. 1 to describe data for hydrolysis of hemicellulose in corn stover in only water by batch and flowthrough systems, respectively. In Figs. 1 and 2, xylan conversion is calculated as the initial mass of xylan minus the mass of xylan at a time t all divided by the initial mass of xylan. Although the data are not presented, acid-catalyzed systems behaved similarly.

A branched pore leaching model as applied to release of water-soluble carbon from soil incorporates reaction to soluble compounds coupled with pore diffusion within the solids and leaching into the bulk solution. Application of such a model appears to describe hemicellulose hydrolysis reasonably well but not significantly better than chemical reaction only or simple leaching models. 

Pentoses contained in hemicellulose are used to produce furfural, a useful industrial chemical, used as a solvent for resins and waxes and in petrochemical refining. It is also used as a feedstock for a range of aromatic substances (it has an almond odour) including preservatives, disinfectants and herbicides. Furfural can be converted to furfuryl alcohol and used to make resins for composite applications with fibreglass and other fibres. These are of interest in the aircraft component and automotive brake sectors. Furfural is commercially derived from acid hydrolysis of waste agricultural by-products, such as sugarcane bagasse, com cobs and cereal brans. Around 450 000 tonnes is produced by this method per year. 

Apart from hemicellulose and cellulose, lignin is also a promising raw material for various applications. Huttermann et al. (2001) described various potential technologies for lignin modification for the production of new compounded materials. Pan et al. (2005) demonstrated that lignin extracted during ethanol organosolv... 

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