By incorporating one bacterium-gene in yeast, researchers from the TU Delft have realized three important improvements in the production of bio-ethanol from agricultural waste: more ethanol, less acetic acid and the elimination of the side product glycerol. Their findings were published in magazine ‘Applied and Environmental Microbiology’.
Bio-ethanol is produced from sugars in plantmaterial by the yeast ‘Saccharomyces cerevisiae’. The yeast is the same micro-organism that produces alcohol in beer and wine. Bio-ethanol is produced by preference from raw materials that do not compete with the food production, such as wheat straw or corn leafs and stalks. By releasing the sugars from this material, a lot of acetic acid also produces. Acetic acid can restrain the production of bio-ethanol by the yeast. Another difficulty is that around 4 percent of the sugar will be lost due to the development of the side-product glycerol. The forming of glycerol was long regarded as an inevitable consequence of the production process.
Researchers of the TU Delft got round this problem. Starting point was that the damaging acetic acid can also be converted into alcohol by the yeast. It seems, only one gene is missing in the yeast. By transferring this missing gene from the bacterium E-coli into the yeast, the researchers from TU Delft and the Kluyver Centre for Genomics of Industrial Fermentation obtained a yeast that transfers acetic acid into ethanol. Due to this adjustment the function of the production of glycerol expires in the entire process.
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