Biomass materials, polysaccharides

The chemical composition of biomass materials is generally discussed in terms of cell wall polysaccharides (cellulose and hemicelluloses), phenolics (lignin and polyphenols), extractives, and ash content. Wood normally contains small amounts of ash (1 percent) and various quantities of extractives... 

Chemical composition, as discussed in the next section, is closely related to the caloric values of biomass, and also affects the efficiency of conversion, particularly when using a biological approach. For example, the presence of phenolics, particularly lignin, presents a major roadblock for enzymatic conversion of polysaccharides to alcohol. The conversion of juvenile biomass has been shown to have a higher moisture content and lower specific gravity than mature wood (47), and may respond more favorably to such a treatment process. The energy conversion of juvenile biomass materials by a thermal or biological methods needs to be explored. 

Hydrothermal technology has emerged as a most powerful tool because of its environmental-friendly approach. Hydrothermally synthesized carbons have been applied in various fields of research including electronics, nanotechnology, mechanical, biotechnology, and biomedical. Conversion of biomass and waste materials into alternative energy sources open new potentials for future research. A considerable amount of research is still required to fully understand the carbonization process of biomass and polysaccharides. 

Bioadsorption can be described as the removal of substances from solution by biomass materials. The biomass materials that have been investigated in bioadsorption studies come under the following categories bacteria, fungi, algae, yeast, waste materials of the food and agricultural industry, lichens and other polysaccharides. 

Polysaccharides. Polysaccharides, also called glycans, are the nutrient and stmctural materials of plants. They are a principle part of the carbohydrate portion of the biomass. The most prevalent monomeric carbohydrate is glucose. Common polysaccharides are all polymers of glucose (Pig. 

Xylan-type polysaccharides are the main hemicellulose components of secondary cell walls constituting about 20-30% of the biomass of dicotyl plants (hardwoods and herbaceous plants). In some tissues of monocotyl plants (grasses and cereals) xylans occur up to 50% [6j. Xylans are thus available in huge and replenishable amoimts as by-products from forestry, the agriculture, wood, and pulp and paper industries. Nowadays, xylans of some seaweed represent a novel biopolymer resource [4j. The diversity and complexity of xylans suggest that many useful by-products can be potentially produced and, therefore, these polysaccharides are considered as possible biopolymer raw materials for various exploitations. As a renewable resource, xylans are... 

Over the past two decades, considerable interest has been directed toward the conversion of cellulosic biomass (such materials as wood wastes, bagasse, and straw) into useful products, notably fuels. Several procedures, including fermentation, gasification, liquefaction, and pyrolysis, have been commercially applied to carbohydrates with various degrees of success. In order to use the polysaccharides present in lignocel-lulosic materials as a substrate in fermentation processes, pretreatments are necessary, such as with steam (under slightly acid conditions) or... 

Estimate the Kihio values (Eq. 10-4) of the two compounds partitioning to the soybean leaves and roots and compare these values with the experimentally determined BAFt values given above. How important are materials contributing to the plant biomass other than the lipids (i.e., proteins, polysaccharides, water) with respect to the accumulation of the two compounds in soybean Use Table 10.2 and Appendix C for solving this problem. 

The present utilization of carbohydrates as a feedstock for the chemical industry is modest, when considering their ready availability, low cost and huge potential [92], The bulk of the annually renewable carbohydrate biomass consists of polysaccharides, but their non-food utilization is still modest. The low-molecular-weight carbohydrates, that is, the constituent units of these polysaccharides, are potential raw materials for several commodity chemicals in fact, glucose (available from cornstarch, bagasse, molasses, wood), fructose (inulin), xylose (hemicelluloses) or the disaccharide sucrose (world production 140 Mtons year-1) are inexpensive and available on a scale of several ten thousands. 

Absorption bands in the typical C—H stretching region at 3000-2870 cm-1 usually showing two maxima at 2925 and 2855 cm-1 related to CH2 and CH3 aliphatic groups. These bands are well defined in the spectra obtained from microbial biomass of soils and there can be assigned to cell wall and capsular polysaccharides (Filip, 1978) 27). But they are also common in spectra of other biological materials. 

The glow electrolysis technique (electrolysis with an anode immersed in the solution and the cathode above the surface) at 600-800 V dc and 300-500 mA converts a solution of starch into ethylene, methane, hydrogen, and both carbon mono- and dioxides.323 Electrochemical methods for converting polysaccharides and other biomass-derived materials have been reviewed briefly by Baizer.324 These methods are mainly oxidations along a potential gradient, which decreases the activation energy of the reactants. Starch in 5 M NaOH solution is oxidized on platinum electrodes to carboxylic acids with an activation energy of about 10 kcal/mol. In acidic media oxidation takes place at C-l followed by decarboxylation and oxidation at the C-2 and C-6 atoms.325... 

Carbohydrates would be the predominant raw materials for future biorefineries. The major polysaccharides found in nature are cellulose, hemicellulose and starch (see Chapter 1). These molecules would be mainly utilised after they are broken down to their respective monomers via enzymatic hydrolysis, thermochemical degradation or a combination of these two. Cellulose and hemicellulose, together with lignin, constitute the main structural components of biomass. Starch is the major constituent of cereal crops. This section would focus on the potential utilisation of carbohydrates and lignocellulosic biomass for chemical production. 

Carbohydrates, in the form of gums, polysaccharides, oligomers, and monomeric sugars, are readily available in large quanitities from renewable biomass resources. Each of these substances, either directly or in a chemically modified form, is a source of intermediates (derivatives) that have potential use in adhesive formulation. Carbohydrates have been utilized historically for and in adhesives and are likely to be used more and more in the future as petroleum-derived chemicals become scarce and prices increase. Appropriate research emphasis can effectively further their use as adhesive raw material. 

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