1 Bioengineering Laboratory, Earth and Life Institute, Catholic University of Louvain, Belgium. Electronic address: Spiros.Agathos@uclouvain.be.
2 Laboratory of Microbial Ecology and Technology, Department of Biochemical and Microbial Technology, Faculty of Bioscience Engineering, Ghent University, Belgium. Electronic address: Nico.Boon@UGent.be.