Biomass polysaccharides

Obtaining a clean fractionation (/) of biomass polysaccharides has been a difficult task. Ultimately, utilization of biomass to produce liquid fuels economically must solve this challenge. Many government agencies (2), national labs (i), industry and academia (4,5,6,7,8) have attempted to solve this problem by almost as many methods and improvements. The reactive nature of... 

Our earlier research established a chemical process (Figure 6) for the production of various hydrocarbon fuels and chemicals ft om biomass polysaccharides (21,22,23). Two steps are required to complete the process from polyols. Polyols are converted into mainly liquid hydrocarbons by reduction with boiling hydriodic acid. Hydrocarbons phase separate and the aqueous acid is recycled. Step 2 converts remaining halocarbons into aikenes. An electrochemical regeneration of the primary reducing solution provides an economically improved process and is e subject of another patent application. 

There are many different routes to organic chemicals from biomass because of its high polysaccharide content and reactivity. The practical value of the conversion processes selected for commercial use with biomass will depend strongly on the availabiUty and price of the same chemicals produced from petroleum and natural gas. 

Hemicellulose [9034-32-6] is the least utilized component of the biomass triad comprising cellulose (qv), lignin (qv), and hemiceUulose. The term was origiaated by Schulze (1) and is used here to distinguish the nonceUulosic polysaccharides of plant cell walls from those that are not part of the wall stmcture. Confusion arises because other hemicellulose definitions based on solvent extraction are often used in the Hterature (2—4). The term polyose is used in Europe to describe these nonceUulosic polysaccharides from wood, whereas hemicellulose is used to describe the alkaline extracts from commercial pulps (4). The quantity of hemicellulose in different sources varies considerably as shown in Table 1. 

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... 

Production of the color involves centrifugal separation of the biomass, cell breakage, and extraction. Use of a salt solution rather than water as an extraction medium increases stability of the color during extraction. Methods for partial exclusion of the polysaccharide from the color extract in order to enhance resolubilization of the dried color were developed. These processes include either microfiltration or co-precipitation of the polysaccharide with an added positively charged polysaccha-... 

Experiments were carried out by varying the amount of inoculum (10, 15 and 20 % v/v) to determine the optimal quantity which ensures a steady growth. The time course of growth of the cell suspensions, inoculated with the corresponding amount of inoculum was traced by day-to-day determining the yield of dry cell biomass (7), while the time course of biosynthesis of extracellular polysaccharides was followed by their daily determination, using the carbazole method (9). 

Isolation of polysaccharide fractions After a growth period of 8 days the cell biomass was separated by filtration and the spent culture medium was used for the isolation of polysaccharides. The following procedures were examined ... 

On the other hand, with cell suspensions synthesizing a considerable amount of polysaccharides, the excessive quantity of inoculum can lead to intensive aggregation before the maximum in the biomass synthesis is reached. 

It is sometimes claimed that mucilage and similar gels may help to maintain hydraulic conductivity between root and. soil (52). However, the hydraulic conductivity of soils is often substantially decreased when soils are irrigated with waste water. Apart from the inducement of sodicity, which is real in many cases, the decreases in hydraulic conductivity are attributed largely to the production of microbial biomass, particularly extracellular polysaccharides (e.g.. Ref. 53). These extracellular polysaccharides form gels that may store large quantities of water and allow water and ions to diffu.se through them at rates not much less than those of free water, but they could be expected to restrict mass flow of water and thus nutrients, to roots (54). 

Upgrading Biomass enzymatic work for non-food uses of the biomass (new lubricants, emulsifiers (biosurfactants), and viscosity agents (polysaccharides)). 

G.R. Ponder and G.N. Richards, A review of some recent studies on mechanisms of pyrolysis of polysaccharides Biomass Bioenerg., 7,1 24 (1994). 

Different routes for converting biomass into chemicals are possible. Fermentation of starches or sugars yields ethanol, which can be converted into ethylene. Other chemicals that can be produced from ethanol are acetaldehyde and butadiene. Other fermentation routes yield acetone/butanol (e.g., in South Africa). Submerged aerobic fermentation leads to citric acid, gluconic acid and special polysaccharides, giving access to new biopolymers such as polyester from poly-lactic acid, or polyester with a bio-based polyol and fossil acid, e.g., biopolymers . 

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