Turn Plants into Biofuel with the Power of Enzymes *
Are biofuels the wave of the future? People often talk about these plant-derived fuels as a way to someday cut down on our dependency on non-renewable carbon-based fuels, like gasoline. Ethanol (a type of alcohol) is a common biofuel used today. In the United States, ethanol is a common biofuel additive to normal gasoline. In fact, some states mandate that when you fill up your gas tank, 10 percent of the total fuel volume be made of ethanol. Brazil, the world's largest user of ethanol-based fuel, has been using ethanol biofuel to power cars since 1975.
Figure 1. The fuel options at this Chevron gas station in California include E85, a gasoline containing 15 percent ethanol by volume. (photo courtesy of Propel Inc., 2011)
There are different types of ethanol-based biofuels, but one that's of growing interest for economic and environmental reasons is cellulosic ethanol. Cellulosic ethanol is made by converting the cellulose found in plant cell walls into ethanol, through a series of chemical reactions, as shown in Figure 2, below. Other types of ethanol use the edible parts of plants that are high in sugar, like corn and sugar cane, but there have been concerns that this is lowering the supply of some foods worldwide. However, cellulosic ethanol has the advantage of being made from the non-edible parts of plants, including corn stalks, citrus peels, and grasses. These are plant parts that are often just thrown away as waste.
Figure 2. Cellulosic ethanol is produced by collecting cellulose from plants (A), isolating the cellulose from the other plant materials (B), using enzymes to break down the cellulose into glucose (C), and then turning that glucose into ethanol through fermentation (D). (Photo courtesy of Bio-Rad Laboratories, Inc.)
One of the challenges has been getting the chemical reactions necessary for cellulosic ethanol production reactions to occur in an efficient manner. This has led scientists to research various enzymes that can help speed up the reactions. One of the enzymes they've discovered is cellulobiase. Cellulobiase (an enzyme in the cellulase family) is used in one of the chemical reaction steps to help convert the cellulose into glucose. The glucose (a type of sugar) can then be fermented to create ethanol. But how does cellulobiase work? How much more efficient is the reaction when the enzyme is added? What conditions are best to maximize the cellulobiase efficiency? Using the Carolina EcoKits®: Ethanol Biofuel kit as a starting place, you can investigate these questions yourself. You can even take the project a step further and look for other naturally occurring enzymes, like others in the cellulose family, and compare their impact on the reaction. Or continue the process and use microbial fermentation to create your own ethanol biofuel. Who knows, you might discover something important to help fuel up today's cars!
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Last edit date: 2018-10-17
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