In the United States, one out of every three corn plants ends in a bio-ethanol plant. Further increases in this share could lead to undesirable competition with food production – unless only non-edible plant waste is converted into bio-ethanol. Professor of Biotechnology Jack Pronk (Applied Sciences) is working on this, in collaboration with the chemical firm DSM. Last September, DSM and an American partner opened their first plant in the USA in which fuel is produced from corn leaves and stalks – the ‘second-generation bio-ethanol’.
The champagne flowed freely, in Delft as well. ‘We had a live feed with the party in Iowa’, recounts Pronk. ‘It was one of the highlights of my career. It is fantastic to see the contributions that our research has made to this achievement.’
Pronk is referring to the yeast cells that his research group has been adapting genetically through years of research, such that they are now able to break down nearly all of the sugars in plant waste. Ordinarily, yeasts convert only sugars that have six carbon atoms (e.g. glucose) into ethanol. The production of second-generation bio-fuels also requires the ability to convert sugars with five carbon atoms, particularly xylose and arabinose.
Ten years ago, Pronk and Prof. Hans van Dijken took the first major step in this direction. A mould that colleagues in Nijmegen detected in elephant manure was found to contain a special gene that would become the key to the conversion of xylose. The TU Delft scientists introduced this gene into the DNA of their yeast cells. Since that time, they have been improving this ‘xylose yeast’ through further genetic modifications and natural selection.