The yeast strain they made can tolerate ethanol concentrations as high as 18 percent--almost double the concentration that regular yeast can handle without quickly dying. In addition, the new strain makes about 20 percent more ethanol by processing more of the glucose, and it speeds up fermentation by 70 percent.
So far the researchers have only modified a laboratory strain of the yeast, not the type now used in ethanol plants. "The next step is to show that this technology works with industry strains," Stephanopoulos says.
If their approach can modify industrial yeast, it would drive down the cost of ethanol, Ladisch says. And eventually this research could have a wider impact, he says, because the mechanism that the researchers used to make the ethanol-tolerant yeast could be used as a blueprint to develop other wanted traits in microbes. "They now have a handle into fundamental metabolic pathways in how the yeast might be modified," he says.
Stephanopoulos believes that cellulosic-ethanol yields could be improved by tailoring certain traits in microbes using his technique. It might be possible to make microbes that are tolerant of compounds other than ethanol that are created in the fermentation process and toxic to the microbes. He also hopes to produce strains that eat sugars with five carbon atoms, such as xylose, that are produced when cellulose is broken down. The microbes used in today's processes only ferment sugars like glucose that have six carbon atoms.
A combination of things need to be developed to enable environmentally clean transportation.
Far lighter vehicles. Using carbon fiber and/or nanograined metals (aluminum is 10 times stronger with nanograin). Lower the overall demand for fuel for transportation with greater efficiency.
Develop and deploy plug in hybrids. We need better batteries for longer range on electricity. 2008-9 plug in hybrids will start to be deployed by Honda, Nissan and Toyota. 100+mpg. With far lighter vehicles could expand the battery powered range. Get the battery range significantly past regular commute distance and fuel use drops to almost nothing.
Expand clean electrical power sources. In the near-mid term, that is mainly nuclear power.
Use genetic engineering to get higher efficiency from crops or microbes to generate more biofuel as described in this article.
Have government policies geared to accelerate the early retirement of inefficient vehicles and provide support for mass transit. Also, support all electric folding bikes and mopeds which would have less of a technological hurdle for clean transportation.
A recent study says hydrogen is more inefficient than electricity as power storage.