Biomass starch

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. 

Phospholylases, as summarized in Table 28.1, catalyze the reversible phospho-rolysis of polysaccharides or oligosaccharides, and produce phosphorylated mono-saccharides. Among such enzymes a-glucan phosphorylase (GP, EC 2.4.1.1), sucrose phosphorylase (SP, EC 2.4.1.7) and cellobiose phosphorylase (CBP, EC 2.4.1.20) are of great interest, since they can produce a-glucose 1-phosphate (a-GlP) from three major biomasses starch, sucrose, and cellulose. Only these three are described in this paper, a comprehensive review of other phosphorylases can be found in Kitaoka and Hayashi (2002). 

Biomass. There are two predominant types of biomass starch and lignocellulosics. Com, wheat, sorghum, and potato are representative of the starch class, whereas agricultural wastes (such as com cobs and stovers, wheat straw, etc.), forestry wastes, and dedicated woody and herbaceous crops comprise the bulk of available and potential lignocellulosics. There is a general consensus that current and future supplies of biomass will not be a limiting factor in the production of organic chemicals (2),... 

The limited quantities of oligomers formed are separated by fractional distillation of n-hexanol. Interestingly, this process competes with the fermentative production of n-hexanol from biomass, starch or cellulose. The third method for the production of n-hexanol is based on the hydrogenation caproic or n-hexanoic acid. 

Recently, however, we have embarked on a programme aimed at developing biodegradable and renewable support materials based on the very abundant sources of biomass such as starch, chitosan and cellulose, in addition to the inorganic materials mentioned above. 

The aim is to produce biomass or a mass of cells such as microbes, yeast and fungi. The commercial production of biomass has been seen in the production of baker s yeast, which is used in the baking industry. Production of single cell protein (SCP) is used as biomass enriched in protein.6 An algae called Spirulina has been used for animal food in some countries. SCP is used as a food source from renewable sources such as whey, cellulose, starch, molasses and a wide range of plant waste. 

Biopolymers derived from biomass such as from agro-resources (e.g., starch, lingo-ceUulosic materials, protein and lipids)... 

Most of the biomass used for energy is burned, either directly to provide heat or in a power station to provide electricity. Although biomass is a complex mixture of starch, cellulose, etc., in simple terms the burning process can be viewed as being represented by Equation 6.1. The CO2 output can be considered as being essentially neutral since a similar amount of CO2 is consumed in growing the biomass. 

Starch and cellulose are potentially important renewable resources for chemical production. Glucose (a component of starch) is relatively easy to obtain from plant material and is used to synthesize existing chemicals. While this is so, the production of such renewable materials, a full fife-cycle assessment of the requirements for their production suggest that much fossil-soiuced energy and material would stiU be employed in the growing, harvesting and processing of biomass. 

Adsorption of azo dyes by the biomass is considered as the first step of their biological reduction [39]. Because of adsorption, the dye is concentrated onto the biomass until its saturation the amount of adsorbed dye is then proportional to the amount of biomass [4CM-2]. Steffan et al. [43] observed that 68% Ethyl Orange was rapidly adsorbed on a microbial consortium immobilized in alginate beads, but only after the addition of glucose or starch the dye was effectively degraded. 

Fermenting grains with yeast produces a grain alcohol. The process also works with other biomass feedstocks. In fermentation, the yeast decomposes carbohydrates which are starches in grains, or sugar from sugar cane juice into ethyl alcohol (ethanol) and carbon dioxide. The process breaks down complex substances into simpler ones. 

Starch and fatty acids are the main food constituents of biomass. Sugar is derived from starch by hydrolysis or directly by extraction from sugar cane or beet. Fermentation converts sugars into alcohol that can be directly used as fuel, or in principle can be used as the raw material of a bioreftnery plant for further upgrading. Triglycerides, derived from oil seeds, are used to be converted into biodiesel through transesterification processes (Fig. 1.14). 

Both in the USA and the EU, the introduction of renewable fuels standards is likely to increase considerably the consumption of bioethanol. Lignocelluloses from agricultural and forest industry residues and/or the carbohydrate fraction of municipal solid waste (MSW) will be the future source of biomass, but starch-rich sources such as corn grain (the major raw material for ethanol in USA) and sugar cane (in Brazil) are currently used. Although land devoted to fuel could reduce land available for food production, this is at present not a serious problem, but could become progressively more important with increasing use of bioethanol. For this reason, it is important to utilize other crops that could be cultivated in unused land (an important social factor to preserve rural populations) and, especially, start to use cellulose-based feedstocks and waste materials as raw material. 

The compactness and complexity of (ligno)cellulose makes it much more difficult to attack by enzymes with respect to starch. Therefore, the cost of bioethanol production is higher [23], To be cost competitive with grain-derived ethanol, the enzymes used for biomass hydrolysis must become more efficient and far less expensive. In addition, the presence of non-glucose sugars in the feedstock complicates the fermentation process, because conversion of pentose sugars into ethanol is less efficient than conversion of the hexose sugars. 

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