They Can Have their Cellulose and Digest it Too
Corn-based ethanol, once the darling of renewable energy enthusiasts, has recently come under heavy criticism from many influential quarters in the science, business and public policy realms for several of its perceived fallacies. Its two main sticking points: low cost-efficiency and upward pressure on food prices.
Indeed, a growing volume of research literature has now shown that more fossil energy is expended to produce ethanol than is actually contained within it, leading many to point to more efficient alternatives such as cellulosic ethanol produced from waste biomass or switchgrass, which are cheap and plentiful. Mariam Sticklen, a professor of crop and soil science at Michigan State University, may have just found the ideal solution to this problem. Cellulose, a complex carbohydrate, requires the presence of enzymes produced by specialized bacteria not typically found in plants to be broken down into usable sugars. Sticklen and her colleagues were able to genetically engineer corn to get it to make the same enzymes that the bacteria normally manufacture. According to Sticklen, the cellulase produced by corn could save about 30 to 50 cents per gallon of ethanol.
To accomplish this, she had to make sure that the enzymes would not break down cellulose in the living plants, a problem she overcame by using an enzyme normally found in bacteria that live in hot springs. Since the enzyme is only active at high temperatures outside the plant's normal physiological threshold, it remains dormant until heated to approximately 50 ºC.
James McMillian, a principal group manager at the National Renewable Energy Laboratory, in Golden, CO, cautions that steps should be taken to ensure that these plants don't have a negative impact on the environment before this scientific breakthrough is implemented on a larger scale. Left-over plant biomass could provide a rich source of easily digestible sugars for microorganisms, whose rapid growth could then lead to changes in ecosystems. ::Technology Review: Cheaper, Cleaner Ethanol from Biotech Corn