Aerobic granular sludge (AGS) is a promising alternative wastewater treatment to the conventional activated sludge system, allowing substantial space, energy and chemichal products savings. Basic understanding of this processes has mainly been obtained in laboratory-scale studies with soluble synthetic wastewaters. Yet, the aspect and performances of granular sludge grown in such model systems are very different from those obtained in reactor treating real wastewater. It is hypothetized that fermentable compounds and hydrolyzable matter can have a major impact on AGS microbial communities. This experiment aims to study the impact of wastewater composition on the AGS microbial communities and their nutrient removal performances. After the first transition from simple to complex soluble synthetic wastewater, the nutrient removal performances were good, but the microbial community shifted from β-proteobacteria to Actinobacteria. In particular, the phosphate accumulating organism (PAO) Candidatus Accumulibacter decreased drastically letting Tetrasphaera be the only PAO present in significant abundance in the sludge.These results confirm the importance of the synthetic wastewater composition on the labscale models for aerobic granular sludge. In particular, Tetrasphaera seems to play an important role in phosphate removal from complex wastewater.