Fermentation Ethanol

Fermented beverages such as beer and wine have been produced for thousands of years from naturally occurring enzymes and yeasts present in grains and fruit. Ancient China is believed to have been the first civilization to produce a distilled alcoholic beverage. In modern times distillation and fermentation efficiencies have been steadily improved. Since about 1960 the use of microbial enzymes and specially selected yeasts have played a major role in North America producing increasingly larger volumes of ethanol from grain for use in the beverage, industrial and fuel markets. In Brazil, sugar cane, which produces the simple sugar sucrose, has been used to produce ethanol for their fuel market. In cooler climates it is more economical to use starch, usually corn (maize), as a fermentable feedstock. However, unlike sucrose, the starch must first be broken down into simple fermentable sugars, such as maltose and dextrose, using enzymes, preferably those obtained from microbial sources.

Corn (maize) can be simply ground, enzymatically hydrolyzed, and then fermented as a whole mash. This is the least capital intensive process to produce fermentation ethanol for industrial and fuel markets. However, most of the fermentation ethanol being distilled is produced from cornstarch that has been removed from most of the other components present in corn such as gluten, germ and fiber. Either way the starch is usually pressure cooked around 105° C in the presence of thermostable alpha amylase and then liquefied further at 85° C. The dextrinized mash is then cooled and saccharified at either 60° C with glucoamylase or simply cooled to 32° C and simultaneously saccharified with glucoamylase and fermented with yeast. The fermentation usually takes 1 – 3 days. The fermented beer normally contains about 18% ethanol before being distilled and processed into nearly a 100% anhydrous form.

Several companies are working on eliminating the need to cook the grain or starch before fermentation. New enzymes that work efficiently at fermentation temperature are expected to help the ethanol industry improve ethanol yield and further reduce the levels of glycerol and organic acids, thereby increasing the level of ethanol.

The U.S. and Canadian markets for fuel ethanol have grown to over 50 billion liters per year. The industrial and beverage markets are much older and more mature, but have surpassed one billion annual liters. These production volumes of fermentation ethanol require large amounts of alpha amylase, glucoamylase and yeast. The enzyme and yeast producers are actively developing new enzyme and yeast technology through intensive strain selection and other modern improvement techniques. Yield and properties of enzymes and yeast have steadily improved, benefiting the fermentation ethanol producers and ultimately the consumers of industrial and fuel ethanol.

Ethanol is a renewable resource that has a high octane rating and is clean burning. These features have given ethanol producers a significant role in replacing tetraethyl lead and MTBE as an octane booster in gasoline. Ethanol’s clean burning properties have helped major metropolitan areas improve their air quality. Protection of our drinking water has become a concern which has allowed ethanol to find new octane and oxygenate markets. The growth of the ethanol industry from grain has also provided a growing market for agriculture. The use of ethanol in fuel is helping to conserve the diminishing supply of oil and extend the oil refining capacity.

The U.S. Department of Energy is actively encouraging industry and others to develop ethanol production from historically more difficult fermentation feedstocks such as rice straw and corn stover. Cellulose and hemicellulose present in straw and stover are less expensive than starch, but are so far more difficult to store, hydrolyze and ferment. Ethanol, enzyme, yeast producers, and others have taken up the task of finding ways to capitalize on the vast opportunity to convert cellulose and hemicellulose as efficiently as starch into ethanol. When successful the annual volume of distilled ethanol in North America could grow several-fold.

Enzyme Development Corporation provides technical service to the fuel ethanol producers in the U.S.