Cereal grains, ethanol production

More recently, interest has developed in the use of enzymes to catalyze the hydrolysis of cellulose to glucose (25—27). Domestic or forest product wastes can be used to produce the fermentation substrate. Whereas there has been much research on alcohol fermentation, whether from cereal grains, molasses, or wood hydrolysis, the commercial practice of this technology is primarily for the industrial alcohol and beverage alcohol industries. About 100 plants have been built for fuel ethanol from com, but only a few continue to operate (28). 

Starch-containing plants Another potential ethanol feedstock is starch. Starch molecules are made up of long chains of glucose molecules. Hence, starch-containing materials can also be fermented after the starch molecules have been broken down into simple glucose molecules. Examples of starchy materials commonly used around the world for ethanol production include cereal grains, potatoes, sweet potatoes and cassava. Typical cereal grains commonly used for ethanol production in the EET are rye and wheat. 

Ethanol production from cereal grains such as barley, wheat and com is a much easier process than from cellulose material. The process includes several steps, as listed below ... 

Sugars are used as fermentation substrates to yield products such as lactic acid, citric acid, and ethanol. Ethanol can be used as a food product, as a food solvent, or as a source for energy. In very recent times, with rapidly escalating demand for power alcohol, concern over the economic impact of this latter usage has raised serious challenges to the availability of sufficient quantities of some cereal grains for food use [82]. 

The industrial production of biobutanol started in 1916 as a fermentation process using bacteria Clostridia acetobutylicum (39). This type of fermentation has been addressed as acetone-butanol-ethanol (ABE) fermentation and is used with molasses and cereal grains. The materials used for ABE fermentation are detailed in Table 11.2. 

To produce ethanol from starchy materials, such as cereal grains, the starch must first be converted into fermentable sugars, which are formed by starch degradation by amylases and maltases (see Section 4.5.6.1.3). For the production of beer, for example, yeast strains are selected that metabolise maltose and maltotriose (which... 

FERMENTATION. Many carbohydrate sources may be fermented for example fruit juices, palm juice, cactus juice, molasses, sugar, honey, milk, potatoes, or cereal grains. Fermentation is the production of ethanol or ethyl alcohol by the action of yeast on carbohydrate as shown in Fig. C-26. 

FIGURE 14.8 Flowchart of the commercial production of fuel ethanol from cereal grains. 

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