Researchers from Delft University of Technology in the Netherlands have overcome three challenges in the production of bioethanol from agricultural waste by inserting a single gene from the bacterium Escherichia coli into the yeast Saccharomyces cerevisiae. The invention is published in this weeks journal of "Applied and Environmental Microbiology".

Long used as a fermenting yeast that produces the ethanol (alcohol) in beer and wine, S. cerevisiae also readily converts the sugars from plant biomass (wheat, corn, etc.) into 'bioethanol' that can used as an alternative fuel source for cars. The trade-off of course is that if these plant crops are used for fuel production, than it decreases the amount available to produce food. So as not to impact traditional food production, manufacturers of bioethanol have turned to using agricultural waste and residues as the source for producing biofuels (known as second generation production) - but this shift has adverse effects on production and quality.

When the sugars from agricultural residues such as wheat straw and corn stover are released, significant quantities of acetate are formed. Acetate slows down and in some cases can even halt the bioethanol production by the yeast. Additionally, during the current bioethanol production process, about 4% of the sugar is lost to the formation of a byproduct, glycerol.

TU Delft researchers have now solved these issues. In theory, yeast should be able to convert the harmful acetate into ethanol as well - it turns out that it is simply missing one gene. By introducing a single gene from the bacterium Escherichia coli, the researchers of the Delft University, working with scientists of the Kluyver Centre for Genomics of Industrial Fermentation enabled this conversion of acetate to ethanol by yeast. This had a two-fold effect - not only did it increase ethanol yields, but it mimicked the normal role of glycerol so efficiently that key genes in glycerol production could be removed, thus completely abolishing glycerol production.

Principal researcher Jack Pronk expresses his excitement; 'In the laboratory, this simple genetic modification kills three birds with one stone: no glycerol formation, higher ethanol yields and consumption of toxic acetate'.

The Delft yeast researchers applied for a patent on their invention and hope to collaborate with industrial partners to accelerate the modified yeasts industrial implementation.

Source: http://www.tudelft.nl/live/pagina.jsp?id=a466a150-8cb1-4f04-8273-f32af61...