"I stayed with this project because I thought it was workable, and I was interested in 'green' chemistry," Ho says. "It's a subject that I feel strongly about and that I've always wanted to research something has to be done to solve our waste and pollution problems."
In 1993, after more than 10 years of dedicated research, Ho's group became the first in the world to produce a genetically engineered Saccharomyces yeast that can effectively ferment both glucose and xylose. Ho first determined that the Saccharomyces yeast needed to produce three strong enzymes for it to efficiently convert xylose to ethanol. She then selected a yeast that could ferment xylose, but which was not effective for fermenting glucose, and cloned from that yeast three genes responsible for producing the xylose-fermenting enzymes. Ho also developed a new method to integrate multiple copies of the three xylose-metabolizing genes into the chromosome of the Saccharomyces yeast.
"Our genetically engineered yeast not only can effectively ferment xylose, but also can ferment glucose and xylose simultaneously to ethanol, a property that no other natural microorganism has," Ho says. "This is important for the industrial production of ethanol, because it takes less time while producing more product."
In addition, the yeast does not require expensive antibiotics to keep the cloned genes active, and the yeast produces very few byproducts, which would have to be removed from the ethanol.
Ho also credits the success of the yeast project to LORRE's director, Professor George Tsao, for his foresight nearly 20 years ago in anticipating the importance of gene cloning technology for the future of biotechnology.
"In 1980 he decided to establish a molecular genetics research group at
LORRE, and he had the courage then to put the responsibility for
est
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Contact: Amanda Siegfried
amanda_siegfried@uns.purdue.edu
765-494-4709
Purdue University
20-Aug-1998