Polysaccharides to monosaccharides

The bioconversion of cellulose into ethanol with conventional methods is usually achieved in two steps first being the enzymatic saccharification of the polysaccharide to monosaccharide and secondly the bioconversion of monosaccharides into ethanol. A combination of enzymatic hydrolysis and ethanol production in the same reactor has been attempted using different cellulases and ethanol producing microbial species to improve process efficiency [46-53]. The production of ethanol from cellulose in a simultaneous saccharification and biological conversion process alleviates the problem of end product inhibition, since glucose does not accumulate in this system and is converted to ethanol immediately following saccharification [46]. 

The use of ILs offers a good solution towards a more efficient transformation of polysaccharides to monosaccharide. But certain issues that arise with ILs must be addressed. ILs still remain expensive and the more work has to be done to reduce their costs as well as to improve on their recovery and reuse. After the pretreatment of lignocellulosic cellulose to remove lignin, methods of recovering the lignin should be explored to further tap its potential to be a combustible material and channeled for different usage. 

Extracts of Flavobacterium heparinum that had been induced to grow on heparin-like polysaccharides contain a number of enzymes that may ultimately degrade heparin and heparan sulfate to monosaccharides.137,145 240 The enzymes that cause the primary cleavage of heparinlike chains are heparinase (EC 4.2.2.7) and heparanase (EC 4.2.2.8, formerly called heparitinase241,242). 

Hydrolysis is the process by which a compound is broken down by reaction with water, thus it can be thought of as the opposite reaction of dehydration, where water is of course removed. Hydrolysis is a key reaction type in biomass chemistry, for it is central in the depolymerisation of polysaccharides to simpler monosaccharide building blocks, such as fructose, glucose, and xylose. 

Two nucleic acids, deoxyribonucleic acid (8.1, DNA) and ribonucleic acid (8.2, RNA), constitute, respectively, the molecules that store hereditary information and those that transcribe and translate such hereditary information, thus enabling the directed synthesis of varied but specific proteins throughout the cell and the entire organism. These nucleic acids are biopolymers, composed of monomeric building units called nucleotides (figure 8.2). Just as proteins can be hydrolyzed to amino acids and polysaccharides can be hydrolyzed to monosaccharides, nucleic acids can be hydrolyzed to nucleotides. 

The monosaccharide D-( + )-glucose, an aldohexose, is formed by plants in photosynthesis and is converted to the polysaccharides cellulose and starch. Simple saccharides are called sugars. Polysaccharides are hydrolyzable to monosaccharides e.g., a mol of trisaccharide gives 3 mol of monosaccharides. 

In a discussion of the use of deamination to obtain structural information, it is convenient to consider two different aspects (a) applications to monosaccharide and cyclitol amines, and (b) applications to compounds containing amino sugar and inosamine residues. The latter compounds would include oligosaccharides, polysaccharides, glycolipids, glycoproteins, and antibiotics. 

Dietary Polysaccharides and Disaccharides Undergo Hydrolysis to Monosaccharides... 

Ingested polysaccharides and disaccharides are converted to monosaccharides by intestinal hydrolytic enzymes, and the monosaccharides then enter intestinal cells and are transported to the liver or other tissues. 

Figure 14.11. Construction of biopolymer with HyperChem. Two menus are available for creating 3D structure models in HyperChem. The Build menu provides tools for creating organic molecules. Use the Drawing tool to sketch atoms in a molecule and connect them with covalent bonds. Invoke the Model builder to create a 3D structure from the 2D sketch. The Databases menu offers tools for creating biopolymers from residues with user specified linkages and conformations—that is, polysaccharides from monosaccharides, polypeptides form amino acids, and polynucleotides from nucleotides. A double-stranded DNA chain, for example, is constructed from nucleotide residues in a desired conformation (the inset).

Polysaccharides A class of high-molecular-weight carbohydrates that can be broken down to monosaccharides on hydrolysis... 

Extracellular polysaccharides are produced by some species of the genus Rhodella, but their composition seems to be even more complex than that of Porphyridium. In addition to monosaccharide components just mentioned, rhamnose and 3-O-methyl-xylose were found in the mucilage of R. maculata.723 724 An extremely complex proteoglycan was shown to be produced by Rhodella grisea.725... 

Reaction with acids in acid medium, disaccharides and polysaccharides may be hydrolyzed to monosaccharides, which in turn may be dehydrated and degraded... 

One of the most common hydrolysis reactions is that required to convert polysaccharides into monosaccharides prior to the determination of total carbohydrates in food and environmental samples. The use of highly acid media (e.g. 12 M sulphuric acid) and elevated temperatures ( 100°C) for 20 min produced partial oxidation of carbohydrates [80]. Using room temperature to avoid oxidation resulted in incomplete hydrolysis [81], and so did lowering the concentration of sulphuric acid to 0.5 M while keeping the temperature at 100°C for 8 h [82-84]. One of the most accurate ways of determining total carbohydrates is by using 1 M HCI at 100°C for 20 h [85,86]. 

The carbohydrate class, polysaccharide, represents compounds in which the molecules contain many units of monosaccharides joined together by glycoside links. Upon complete hydrolysis, a polysaccharide delds monosaccharides. Starch is the most valuable polysaccharide. The starch molecules (amylose and anylopectin) are tree-like, containing 250 to 1000 or more glucose units per molecule joined together through alpha linkages. 

Polysaccharides may contain, in addition to monosaccharide units, ester, ether, and/or cyclic acetal moieties ( Fig. 2). 

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