Letteratura scientifica selezionata sul tema "Hexose sugar"

This chapter contends that bioethanol has received the most attention over other fuels due to less emission of greenhouse gases and production from renewable sources. It is mainly produced from sugar containing feedstocks. Since feedstocks are utilized as food for humans, its consumption in bioethanol production creates a food crisis for the entire world. Bioethanol derived from agriculture waste, which is most abundant at global level, is the best option. Agriculture wastes contain lignin, cellulose and hemicelluloses which creates hindrances during conversion to ethanol. Pretreatment of agriculture wastes remove lignin, hemicelluloses and then enzymatically hydrolyzed into sugars. Both pentose and hexose sugars are fermented to bioethanol. There are still various problems for developing an economically feasible technology but a major one is the resistance to degradation of the agricultural material. Use of two or more pretreatment methods for delignification and the use of genetically modified agricultural biomass can be developed for economically feasible ethanol production.

This chapter contends that bioethanol has received the most attention over other fuels due to less emission of greenhouse gases and production from renewable sources. It is mainly produced from sugar containing feedstocks. Since feedstocks are utilized as food for humans, its consumption in bioethanol production creates a food crisis for the entire world. Bioethanol derived from agriculture waste, which is most abundant at global level, is the best option. Agriculture wastes contain lignin, cellulose and hemicelluloses which creates hindrances during conversion to ethanol. Pretreatment of agriculture wastes remove lignin, hemicelluloses and then enzymatically hydrolyzed into sugars. Both pentose and hexose sugars are fermented to bioethanol. There are still various problems for developing an economically feasible technology but a major one is the resistance to degradation of the agricultural material. Use of two or more pretreatment methods for delignification and the use of genetically modified agricultural biomass can be developed for economically feasible ethanol production.

Bioproducts—chemical substances or combinations of chemical substances that are made by living things—range from methanol to whole cells. They are derived by extraction from whole plants and animals or by synthesis in bioreactors containing cells or enzymes. Bioproducts are sold for their chemical activity: methanol for solvent activity, ethanol for its neurological activity or as a fuel, penicillin for its antibacterial activity, taxol for its anticancer activity, streptokinase (an enzyme) for its blood clot dissolving activity, hexose isomerase for its sugar-converting activity, and whole Bacillus thuringiensis cells for their insecticide activity, to name a few very different examples. The wide variety represented by this tiny list makes it clear that bioseparations must encompass a correspondingly wide variety of methods. The choice of separation method depends on the nature of the product, remembering that purity, yield, and activity are the goals, and the most important of these is activity. This first chapter therefore reviews the chemical properties of bioproducts with themes and examples chosen to heighten awareness of those properties that must be recognized in the selection of downstream processes that result in acceptably high final purity while preserving activity. The final part of this chapter is an introduction to the field of bioseparations, which includes a discussion of the stages of downstream processing, the basic principles of engineering analysis as applied to bioseparations, and the various factors involved in developing a bioproduct for the marketplace. The pharmaceutical, agrichemical, and biotechnology bioproduct industries account for many billion dollars in annual sales—neglecting, of course, commodity foods and beverages. By “bioproduct” we mean chemical substances that are produced in or by a biological process, either in vivo or ex vivo (inside or outside a living organism). Figure 1.1 indicates a clear inverse relationship between bioproduct market size and cost. Owing to intense competition, cost, price, and value are very closely related, except in the case of completely new products that are thoroughly protected by patents, difficult to copy, and of added value to the end user.