The experiments show that I. sakaiensis ferments PET or EG to acetate and ethanol while G. sulfurreducens uses the fermented acetate as the substrate for the electricity production while releasing CO2. Overall, the symbiotic system shows a consumption of 16.7 mM EG after 6 d (Figure ) which is converted via acetate into electricity and CO2 and also serves as the carbon source for cell growth of I. sakaiensis and G. sulfurreducens. In contrast, the monoculture only showed a conversion of 9.7 mM after 6 d (Figure ). This 1.7-fold increase in the EG consumption in the co-culture suggests that the metabolism of EG by I. sakaiensis was enhanced when the strain was grown together with G. sulfurreducens, where acetate is constantly being consumed. A classic example for the enhanced metabolism in a co-culture system is nitrification. In this syntropic process, ammonium-oxidizing bacteria (AOB) oxidize ammonia to nitrite while nitrite-oxidizing bacteria convert nitrite further to nitrate. This concert operation has been shown to accelerate the performance of AOB .