降低生物燃料的成本

One reason that biofuels are expensive to make is that the organisms used to ferment¹（发酵） the biomass cannot make effective use of hemicellulose（半纤维素）, the next most abundant cell wall component² after cellulose. They convert only the glucose³ in the cellulose, thus using less than half of the available plant material. "Here at the EBI and other places in the biofuel world, people are trying to engineer microbes that can use both," said University of Illinois microbiologist Isaac Cann. "Most of the time what they do is they take genes⁴ from different locations and try and stitch all of them together to create a pathway that will allow that microbe to use the other sugar."   Cann and Rod Mackie, also a U of I microbiologist, have been doing research at the Energy Biosciences Institute on an organism that they think could be used to solve this problem.   Mackie, a long-distance runner, found the microbe in the garbage dump of a canning plant while running in Hoopeston, Ill., in 1993. He noticed that the ground was literally⁵ bubbling with microbial activity and took samples. He and his son Kevin, who was in high school at the time, isolated⁶ microbes from the samples.   Among these was a bacterium⁷ that was later named Caldanaerobius polysaccharolyticus. "We found many exciting enzymes⁸ from this organism," said Cann, who joined the project when he came to Mackie's lab as a postdoctoral researcher.   Specifically, the bacterium contains all of the proteins and enzymes needed to break down xylan, which is the most common hemicellulose, and then to transport the fragments into the cell and metabolize them. All of the genes are located in a single cluster on the microbe's genome.   "So instead of taking a piece from here and from there and stitching them together, we can just take this part of the gene," Cann explained. "You can cut this and put it into another microbe."