Alcohol biological conversion

Recovery of Riologieal Conversion Products Biological conversion produces that can be derived from solid wastes include compost, methane, various proteins and alcohols, and a variety of other intermediate organic compounds. The principal processes that have been used are reported in Table 25-64. Composting and anaerobic digestion, the two most highly developed processes, are considered further. The recovery of gas from landfills is discussed in the portion of this sec tion dealing with ultimate disposal. 

Biological conversion to protein Protein, alcohol Shredding, air separation Technology on pilot scale only... 

Several different processes have been proposed for the conversion of solid organic wastes to a more usable liquid or gaseous form to be utilized as fuel or petrochemical feedstocks. Principally the commonly discussed processes involve the biological conversion to alcohols, the catalytic chemical conversion to methanol or Fischer-Tropsch liquids via a carbon monoxide and hydrogen synthesis gas, or the thermochemical formation of gases or oxygenated liquids by pyrolysis. Pyrolysis is defined as the decomposition of organic material at elevated temperatures. The process to be described uses a very special case of pyrolysis. 

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. 

Several approaches have been proposed for the production of liquid fuels from biomass. Alcohol production via fermentation is state-of-the-art technology for specific feedstocks (grain etc.). The use of non-food sources (urban refuse, industrial wastes, etc.) is not fully developed. Processing times are on the order of days however for biological conversion. Non-biological methods fall into two categories (1) direct liquefaction, and (2) indirect liquefaction. Both involve a thermal conversion step. Direct liquefaction... 

Cheng Q, Thomas SM, Rouviere P. (2002). Biological conversion of cyclic alkanes and cyclic alcohols into dicarboxylic acids biochemical and molecular basis. Appl Micmbiol Biotechnol, 58, 704—711. 

Lipases are enzymes that catalyze the in vivo hydrolysis of lipids such as triacylglycerols. Lipases are not used in biological systems for ester synthesis, presumably because the large amounts of water present preclude ester formation due to the law of mass action which favors hydrolysis. A different pathway (using the coenzyme A thioester of a carboxylic acid and the enzyme synthase [Blei and Odian, 2000]) is present in biological systems for ester formation. However, lipases do catalyze the in vitro esterification reaction and have been used to synthesize polyesters. The reaction between alcohols and carboxylic acids occurs in organic solvents where the absence of water favors esterification. However, water is a by-product and must be removed efficiently to maximize conversions and molecular weights. 

The separations so far referred to have involved conversion of the polyhydric compounds into volatile derivatives, but polyhydric alcohols may be separated directly on a column of Polypak. 473 This method has been used to determine such compounds in biological media. 

ENZYME. An enzyme is a protein that serves as a catalyst for a particular biological transformation—as, for example, the conversion of sugar into alcohol and water. Because of the make-up of the genetic material, most enzymes are highly specific. As discussed in the article on Industrial Biotechnology, this specificity is very advantageous in bioprocessing. 

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