Among alternative renewable fuels currently being researched for efficacy, algae has sparked considerable interest. Some of its potential advantages over other biofuels include its ability to be grown in areas unsuitable for either growing typical vegetable food crops such as corn or for raising animals for meat. Switchgrass and wood are both renewable and can be grown on land unsuitable for crops or grazing, but both contain lignin, a polymer made by plants to strengthen their cell walls. The presence of lignin makes it much harder to extract the sugars needed to make alcohol from these plant sources. Algae do not contain lignin but the effort to extract sugars is hampered by the fact that much of their sugar is polymerized to form a complex chemical called alginate which cannot be easily converted into ethanol by current industrial microbes (yeast or bacteria).
This then becomes the bioengineering challenge. Can we genetically alter yeast or bacteria sufficiently to give them the ability to digest alginate and efficiently covert the resulting sugars into ethanol? To date, the story is a fascinating example of our current state of molecular biology and our ability to alter the chemistry and genetics of these micro-organisms without inhibiting their extraordinary ability to multiply.
Researchers in Berkeley, California, began with E. coli, the common (usually harmless) bacteria of our intestinal tract. They extracted a gene from a marine bacterium that makes an enzyme that breaks alginate down into small fragments and put that gene into E.coli. From another micro-organism they obtained a gene that enabled the E. coli to excrete this enzyme into the culture medium, and then another gene was introduced to allow the bacteria to take up the resulting small fragments of alginate. Finally, from a fourth bacterium they had isolated from fermented cane juice, they obtained a gene that, when introduced into their E. coli, turned the alginate fragments into ethanol with high efficiency.
The resulting bacterial Frankenstein, when fed a soup of common brown seaweed, rapidly brewed the mixture to a 5% alcohol concentration. It proved to be twice as good as currently existing algae fermentation procedures for seaweed and achieved more that 80 percent of the theoretical maximum obtainable yield of alcohol. All the wastes from such an operation remain fully biodegradable and, unlike switchgrass, wood or corn, the process does not require land that would otherwise be valuable for growing food crops.
The drawbacks to this process include the following: Growing enough of the appropriate algae would require large areas of the ocean along marine shorelines (in order to allow easy transportation of the fuel stock either by sea or by land). Furthermore, the ocean area required to grow enough algae to supply all the fuel for the United States is reported to be about half the size of the State of Maine, or approximately 15,000 square miles of ocean, enough to remove a significant area from supporting either near-shore fishing or the growing of oysters, clams, mussels and lobsters. However, neither of these drawbacks would seem sufficient to negate using this process altogether.
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