Biopolymers Conference

 Using bacteria to replace plastics derived from fossil oil  This is achieved by bacteria called Ralstonia eutropha or Cupriavidus necator, also known as oxyhydrogen bacteria. We let them sweat away for us,” Riedel jokes. “We place them in a mineral salt solution and feed them with nitrogen, phosphorous, oxygen and carbon. The carbon is added in the form of waste fats. Then we let the bacteria grow. After a certain time, we remove the nitrogen from the bacteria. They react to this deficiency by storing the now excess carbon in the waste fat as an energy reserve in their cells and converting it into PHAs. If after a certain time we were to start adding nitrogen again, the bacteria would start using the PHAs stored within the cells as a source of energy. Of course, we don’t do this because our aim is to harvest the PHAs produced in the cells. This we do by extracting them using solvents which we can partly recover once the process is complete,” explains Riedel.