Metabolic engineering of Saccharomyces cerevisiae for improved polyphosphate production

Finite high-grade phosphate rock reserves and rising legislative demand for phosphorus recycling create a need for processes converting phosphorus-containing residual streams into valuable products. Microbial synthesis of inorganic polyphosphate (polyP) could complement its energy-intensive chemical manufacturing while enabling phosphorus recovery in a value-added product with applications ranging from food processing to flame retardants and fertilizer. After orthophosphate (Pi) starvation and refeeding, Saccharomyces cerevisiae naturally accumulates polyP as a cellular Pi reserve, but the current multistage process complicates industrial implementation. Here, we identified metabolic interventions that uncouple polyP accumulation from Pi starvation by systematic evaluation of 57 engineered S. cerevisiae CEN.PK113-7D strains. Constitutive activation of the PHO regulon produced the strongest increase in polyP, whereas disruption of inositol pyrophosphate synthesis, Pi import, or the vacuolar transporter chaperone complex impaired accumulation. This pattern indicates that efficient polyP accumulation depends on coordinated activation of Pi acquisition and vacuolar polymerization. Notably, deletion of PHO80 converted a transient starvation response into a constitutive production phenotype, enabling high polyP accumulation during growth. Optimization of the growth medium increased the polyP content further, and efficient use of the supplied Pi was demonstrated, while electron microscopy paired with energy-dispersive X-ray spectroscopy supported increased vacuolar storage. During aerobic exponential fed-batch cultivation, pho80Δ simultaneously formed biomass and polyP, reaching a polyP content of 22.1% of cell dry weight and a titer of 8.2 g/L, both expressed as KPO3 equivalents. These findings establish S. cerevisiae pho80Δ as a promising platform for biological polyP production and phosphorus recovery.