Ethanol from cellulose, source

For additional information on the production of ethanol, see the essay Biofuels that precedes Experiment 27. In this essay, the production of ethanol from corn for use in automobiles is discussed, along with the production of ethanol from other sources such as plant cellulose. 

Demirbas, A. Bio-ethanol from cellulosic materials a renewable motor fuel from biomass. Energy Source 2005,27, 327-331. 

Most economic evaluations of the saccharification process (21,22,23) conclude that at the present time the cost of production of the most favoured products (glucose, single cell protein, ethanol) is higher than production from non-cellulosic sources. Nyiri (24) made an economic evaluation of cellulose-based single cell protein and ethanol production. He suggested that an economical plant output is between 7 and 20 m /year, and, depending on the size and complexity of the plant, estimated capital costs between 6 and 12 million. 

See alcohol, denatured alcohol, industrial biomass. Note Ethanol from fermentation of biomass and hydrolysis of cellulose is a significant alternate energy source, especially as an automotive fuel. Its use in gasoline will continue to increase. 

Ethanol is the only renewable liquid fuel made in commercial quantities and supplies about 1% of the gasoline type transport fuels used in the USA. Approximately 95% of the commercial production of ethanol in the USA is currently by direct fermentation of com-sourced carbohydrates. However, fermentation of synthesis gas has the advantage over direct fermentation of sugars from cellulose and the hemicelluloses in that all wood components, including lignin and bark, are suitable feedstocks. 

Because of unfavorable sorption effects on paper that cause tailing, materials with lower adsorptivity were sought. Thus, cellulose acetate [35] and nitrocellulose [36,37] membranes were introduced. Cellulose acetate can be either prepared in the laboratory by treating cellulose with acetic anhydride, or it may be purchased from commercial sources. Cellulose acetate membranes are readily soluble in phenol, glacial acetic acid, dichloromethane and acetone. In part they can be solubilized in several solvent mixtures e.g., chloroform/ethanol (9 1 v/v). For detection (optical scanning) the foil can be made translucent by immersion in cottonseed oil, decalin, liquid paraffin or Whitemore oil 120. 

Although no enzyme capable of synthesizing cellulose has as yet been obtained from plant sources, a similar substrate was prepared by extracting pea seedlings with 80% ethanol. When this material was incubated with ultrafiltered supernatant liquor of Acetobacter, cellulose microfibrils were obtained. ... 

Csllobiose and Cellulose Fermentation Although some wild-type strains of E. coli can utilize cellobiose as a sole carbon source, its metabolism has not been careMly examined (Moniruzzaman et al., 1997). To confer the ability to ferment cellobiose, the casAB operon from Klebsiella oxytoca was introduced into E. coli. Klebsiella oxytoca contains a PTS, which enables it to utilize cellobiose. The K. oxytoca casAB operon, which encodes an enzyme II cellobiose and a phospho-p-glucosidase, was expressed in E. coli KOI 1. Unfortunately, expression was very poor. However, spontaneous mutants with 15-fold higher specific activities for cellobiose utilization were isolated. The best mutant produced 45 g/L ethanol with 94% of the theoretical yield. Two of the mutants were tested for their ability to produce ethanol from mixed waste office paper. The engineered strain produced 32.7 g/L ethanol with 72% of the theoretical yield. 

Ethanol can be produced from any source containing appreciable amounts of sugar or materials such as starch and cellulose that can be converted into sugar (Figure 4A.24). 

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