Fermentation to produce ethanol

Although the use of fermentation to produce ethanol is an ancient technology, more efficient immobilized-cell, continuous processes have been conceived, and Japan has estabhshed the first demonstration-scale plant. 

Warren, R.K., Hill, G.A. and Macdonald, D.G., Continuous cell recycle fermentation to produce ethanol. Food Bioprod. Proc., 72 (1994) 149-157. 

Some whey has found alternative applications, such as fermentation to produce ethanol. 

By-products of starch refining and HFCS prodnction are significant and rednce HFCS production costs by 30 5% (Table 4.2). This is because the com is 70% starch on a dry weight basis, it also contains 10% protein, 4.5% fat and 2.7% erode fibre. In addition much of the glucose syrup produced is fermented to produce ethanol for fuel use. 

An additional feature is that the glucose syrups can also be fermented to produce ethanol for use in fuels. Obviously HFCS is a more valuable product, but power ethanol production does generate significant revenues. 

In a conventional dry grind process, ground com is mixed with water to produce slurry. The slurry is cooked the slurry starch liquefied, saccharified and fermented to produce ethanol. The remaining nonfermentables (germ, fiber, and protein) are recovered at the end of the dry grind process as an animal food co-product, called distiller dried grains with solubles or DDGS. 

GJ/tonne. In normal operations this would be delivered by fuel oil or gas, but in totally renewable operations this heat input may be by burning waste produced from the production of starches and sugars used in the fermenting to produce ethanol, e.g. bagasse. 

Wood is about 65—75% carbohydrate and has been considered as a potential source of ethanol for fuel. The carbohydrate material can be hydrolyzed to monomer sugars, which in turn can be fermented to produce ethanol. However, wood carbohydrates are expensive to hydrolyze. Hydrolysis with acids and enzymes is impeded by the crystalline structure of cellulose. Lignin interferes with processing, and hydrolytic by-products such as furfural, acetic acid, and derivatives of lignin and extractives can inhibit fermentation. Research is still being conducted on wood hydrolysis to develop a process that is economically sound. Furfural is a useful chemical feedstock and results from the dehydration of pentose sugars. It can be obtained in 9 to 10% yield from the dilute acid hydrolysis of hardwoods (75). 

Based only on market penetration projections, processes that appear to offer minor future contributions include marine crops, catalytic liquefaction, and fermentation to produce ethanol. Missions that appear to have greater near-term commercialization potential include ... 

ANAEROBIC CARBOHYDRATE METABOLISM Yeasts growing in media containing high concentrations of fermentable carbohydrate invariably metabolize it fermentatively to produce ethanol and CO2. If air is present, and when the sugar concentration has been lowered, the ethanol is respired using the metabolic routes described above. Under the anaerobic conditions of a brewery fermentation the hexoses derived from wort fermentable carbohydrates are catabolized by the EMP pathway (Fig. 17.2) to pyruvic acid. The pyruvate produced is decarboxylated by the enzyme pyruvate decarboxylase, with the formation of acetaldehyde and CO2. The enzyme requires the cofactor thiamine pyrophosphate (TPP) for activity and the reaction is shown in Fig. 17.10. The acetaldehyde formed acts (in the absence of the respiratory chain) as an electron acceptor and is used to oxidize NADH with the formation of ethanol ... 

Ultrafiltration (UF) is another membrane separation method used to purify liquids. UF is commonly used for recovery of proteins and in food and pharmaceutical applications. It is useful for separating permanent emulsions since the oil droplets will not pass through the membrane. UF is used for the removal of fine colloidal particles, and for recovery of dyes from wastewater. In many applications such as whey processing UF and RO are used in series. The valuable proteins are recovered by UF, and permeate from the UF system is sent to the RO system. The remaining sugars and salts are concentrated in the RO system by removing water. The concentrated permeate can then be fermented to produce ethanol, lactic acid or other products. 

Fermentation to produce ethanol (from sugar) or methane... 

A related process, Broin Fractionation (BFRAC), announced in 2005, first separates corn into three fractions—fiber, germ, and endosperm. The endosperm is fermented to produce ethanol and the other fractions are converted to animal feed. U.S. Patent Application 20110111085. 

At a winery, glucose (C5H12O5) in grapes undergoes fermentation to produce ethanol (C2H5O) and carbon dioxide. (7.7)... 

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