SURFACE ADSORPTION AND ENZYMATIC HYDROLYSIS OF POLYPHOSPHATES – IMPLICATIONS FOR UNDERSTANDING THE BIOGEOCHEMICAL CYCLING POLYPHOSPHATE

Synthesized and accumulated by a vast variety of bacteria and planktons, polyphosphates (polyP) constitute a significant portion of phosphorus (P) in dissolved phase, sinking particulates and sediments in aquatic environment, making them a key player in global P cycling. Despite their environmental significance, little is known about their transport and fate. This work investigated the mineral adsorption, enzymatic hydrolysis and transformation of linear polyP with different chain lengths. The adsorption of these polyP onto iron and aluminum oxide minerals was studied by quartz crystal microbalance with dissipation (QCM-D) and ³¹P solid state nuclear magnetic resonance spectroscopy (NMR). Results suggested that polyP were irreversibly adsorbed with a “side-on” configuration on the minerals, and the adsorption amount was dependent on chain length and pH. The polyP can be catalytically hydrolyzed by alkaline phosphatase, and most likely through the terminals, as supported by ³¹P liquid NMR. In the presence of Ca²⁺, calcium phosphate precipitate formed and was identified to be amorphous, as suggested by Fourier transform infrared spectroscopy (FTIR) and scanning electron microscopy with X-ray microanalysis. Results from this study provide a mechanistic understanding of reactions governing the mobility and transformation of polyp in aquatic environment, therefore, improves our understanding of the P cycle.