Yeast strain development for enhanced polyphosphate production

Phosphate is a crucial finite raw material that is considered to be depleted in the next hundred years. Its polymer polyphosphate can be found in all living organisms and is used for example in food, fertilizer, and industrial applications. Saccharomyces cerevisiae can take up phosphate and accumulate it in high amounts as polyphosphate in its vacuole. This study aimed to improve polyP production by constructing S. cerevisiae strains with enhanced polyP content and an increased average polyP chain length using metabolic engineering. Five genes have been identified in literature that play important roles in polyP degradation. So, these genes were deleted individually and in combinations. Three of the mutant strains with different deletion combinations of the genes coding for the vacuolar phosphatases Ppn1p and Ppn2p, the phosphate exporter Pho91p, and the predicted phosphate exporter Syg1p showed an altered polyP production. The polyP cell content in the yeast with these genetic modifications was increased 3 fold (20.5 % (KPO3) per cell dry weight), while the average chain length was extended 3 fold (30 P subunits) independent of the deletion strain. It was shown that polyP production can be enhanced by genetic engineering without affecting cell growth and viability. By transferring this strategy to industrially relevant strains, it will be possible to make bio polyphosphate synthesis more economical.