Saturday, May 20, 2006

"Ethanol Production" - Nancy Ho

Nancy Ho is the leader of the Laboratory of Renewable Resources Engineering at Purdue Univerity and has developed recombinant strains of yeast with 20-30% increases in yield of ethanol fermentation (I think that's how the moderator introduced her).

Plants are abundant across the plaent, and cellulose comprises about 45% of the plant; over 75% of the cellulose can be converted to sugars, which in turn can be converted by yeast into ethanol. "There is no other natural organism better at fermenting sugars into ethanol than yeast." However, Saccharomyces is missing some metabolic machinery needed to utilize xylose, which is a significant componant of those sugars that can be made from cellulose.

I have a hard time understanding the details, but apparently Dr. Ho caused the gene for D-Xylulose (and other genes related to it in the metabolic pathway? KK, AR, KD?) to be greatly overexpressed by transforming industrial strains of yeast with a plasmid. Experiments showed ethanol concentration increased as glucose and xylose decreased as the transformed strains fermented the sugars; it worked. Glucose is almost completely used within the first 10 hours of fermentation, whereas xylose isn't depleted for more than 30 hours. Dr. Ho explained that xylose is transported into the cell by glucose transporters, which bind glucose 100 times more strongly than xylose - this explains the slower usage of xylose.

Dr. Ho mentioned some kind of legal pressures drove them to work with a new strain of yeast to avoid letting a single company control the product of their research.

Dr. Ho's powerpoint consisted of approximitely 400 graphs, capped by intro and thank you slides (and there may have been a couple non-graphs slides sprinkled in between).


churchill said...


I'm trying to find out how recent this is - you published at 12.57 but in which year?

Mike B

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