|(Image: Jamie Cate and Susan Jenkins, UC Berkeley & EBI)|
Why should we care what yeast are able to digest? The biofuels industry has been struggling to make cellulosic ethanol economically feasible. Right now the industry is using brewers yeast, the single-celled fungus (Saccharomyces cerevisiae) to turn sugar or other simple carbohydrates into alcohol. So far cellulose has been a bit of a problem as it is a pretty tough molecule; it is composed of glucose (simple sugar) molecules all linked together into long chains. Its a molecule that you can find in abundance in various materials such as corn stalks, leaves and cobs (and the US uses a whole lotta corn!) as well as paper waste or any other plant material. Normally these long chains have to be broken up into smaller cellodextrins by enzymes called cellulases using a method called saccharification. Then another enzyme called beta-glucosidase is added to break down the cellodextrins into their simple sugar components. That's all before the yeast even get introduced to the system! If the N. crassa genes (cellodextrin transporters) can be inserted into the industrial strains of yeast that are currently being used for ethanol production the efficiency of the fermentation process can be greatly improved.
The paper appeared in this weeks ScienceExpress:
Galazka, Jonathan M., et al. (2010) Cellodextrin transport in yeast for improved biofuel production. Science: published online. (DOI: 10.1126/science.1192838)
Here is UC Berkeley's new article about the paper: