At the beginning of the 20th century, several kinds of raw materials were
exploited for ethanol production, such as molasses or agricultural production, and the
possibility of hydrolyzing lignocellulosic materials was investigated (Roehr, 2001).
Carbohydrate-rich raw materials suitable for ethanol production can be classified into
three groups of agricultural products: which all sugar, starch and lignocellulose. The
first raw material group, sugar refers to sugar-beet as well as sugarcane and molasses.
The second group, starch from such crops as cassava, cereals and potatoes. The last
group, lignocellulose, covers waste materials from the harvesting of agricultural crops
such as rice straw, corn cob and sugarcane waste (Mogg, 2004).
In general, industrial yeast strains are able to grow and efficiently ferment
ethanol at pH values of 3.5-6.0 and temperatures of 28-30° C, with efficiency
dropping off rapidly at higher temperature. According to Roehr (2001), there are
several potential benefits of thermotolerant yeast for using in the production of
industrial alcohol as follows:
a. Thermotolerant yeast exhibits rapid metabolic activity and a high
fermentation rate with high product output.
b. The solubility of oxygen and other gases in the fermentation broth
decreases with increasing temperature. This phenomenon supports the establishment
and long-term maintenance of anaerobic conditions.
c. The viscosity of the fermentation broth decreases with increasing
temperature. Therefore, the energy required to maintain proper agitation of the growth
media is reduced.
d. The metabolic activity of microbes and frictional effects of agitation serves
to generate large amounts of heat. Thus, additional energy to maintain the vessels at
At the beginning of the 20th century, several kinds of raw materials were
exploited for ethanol production, such as molasses or agricultural production, and the
possibility of hydrolyzing lignocellulosic materials was investigated (Roehr, 2001).
Carbohydrate-rich raw materials suitable for ethanol production can be classified into
three groups of agricultural products: which all sugar, starch and lignocellulose. The
first raw material group, sugar refers to sugar-beet as well as sugarcane and molasses.
The second group, starch from such crops as cassava, cereals and potatoes. The last
group, lignocellulose, covers waste materials from the harvesting of agricultural crops
such as rice straw, corn cob and sugarcane waste (Mogg, 2004).
In general, industrial yeast strains are able to grow and efficiently ferment
ethanol at pH values of 3.5-6.0 and temperatures of 28-30° C, with efficiency
dropping off rapidly at higher temperature. According to Roehr (2001), there are
several potential benefits of thermotolerant yeast for using in the production of
industrial alcohol as follows:
a. Thermotolerant yeast exhibits rapid metabolic activity and a high
fermentation rate with high product output.
b. The solubility of oxygen and other gases in the fermentation broth
decreases with increasing temperature. This phenomenon supports the establishment
and long-term maintenance of anaerobic conditions.
c. The viscosity of the fermentation broth decreases with increasing
temperature. Therefore, the energy required to maintain proper agitation of the growth
media is reduced.
d. The metabolic activity of microbes and frictional effects of agitation serves
to generate large amounts of heat. Thus, additional energy to maintain the vessels at
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