Metabolic Traits\nof Candidatus Accumulibacter\nclade IIF Strain SCELSE‑1 Using Amino Acids As Carbon Sources\nfor Enhanced Biological Phosphorus Removal

Despite recent evidence from full-scale plants suggesting\nthat Candidatus Accumulibacter may be capable of\nusing amino\nacids, this metabolic trait has never been confirmed in a bioreactor\nexperiment. Here we show that an enriched culture of Ca. Accumulibacter clade IIF strain SCELSE-1 could metabolize 11 of\n20 α-amino acids, with aspartate, glutamate, asparagine, and\nglutamine resulting in the highest phosphorus removal. The anaerobic\nuptake of aspartate and glutamate was achieved through a glutamate/aspartate-proton\nsymporter fully powered by the proton motive force (PMF). Under anaerobic\nconditions aspartate was deaminized and routed into core carbon metabolic\npathways to form polyhydroxyalkanoates (PHA). The lack of genes encoding\nNADH dependent isocitrate dehydrogenase in the Ca. Accumulibacter genome resulted in a kinetic barrier for glutamate\nto be channelled to the TCA cycle. Glutamate was stored as glutamate\npolymer. When amino acids (aspartate or glutamate) and acetate were\nsupplied together, Ca. Accumulibacter took up both\ncarbon sources simultaneously, with the uptake rate of each carbon\nsource largely preserved. Overall energy savings (up to 17%) were\nachieved under mixed carbon scenarios, due to the ability of Ca. Accumulibacter to rearrange its anaerobic carbon metabolism\nbased on the reducing power, PMF and ATP balance.