Effect of different nutrient decoupling strategies on aerobic polyhydroxybutyrate production and microbial community

초록

Polyhydroxybutyrate (PHB) production by mixed microbial cultures can recover wastewater carbon as a biodegradable polymer, but the effects of nutrient placement in single-stage nutrient-decoupling systems remain unclear. Four sequencing batch reactors were operated for 420 days under control, ammonium-decoupled, phosphate-decoupled, and combined-decoupled conditions at three nutrient concentrations with a fixed feastto-famine ratio of 0.20. Ammonium placement, rather than total dose, primarily controlled feast length, while feast-phase phosphate availability accelerated stabilization. Feast-phase ammonium limitation directed 56-63% of acetate carbon to PHB, whereas phosphate limitation produced similarly high end-of-feast PHB contents partly through residual PHB carry-over. Famine-phase ammonium further promoted biomass growth using stored PHB. Across twelve steady-state conditions, PHB productivity increased with specific acetate uptake rate, whereas PHB yield decreased, indicating a productivity-yield trade-off linked to microbial community shifts. Nitrincola was strongly associated with high acetate uptake and PHB storage rates. Fed-batch accumulation reached 58 wt% PHB, and communities with high storage capacity on synthetic medium largely retained this phenotype on fermented waste activated sludge. These results identify phase-specific ammonium supply as a key operational lever for directing carbon between PHB storage and biomass growth.

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