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Phosphate is mined from phosphate rock, which is a limited resource on a human time scale. For a sustainable phosphate supply, strategies for efficient use and recycling of phosphate must be developed. A German chemical company produces annually wash water containing phosphate and other inorganic substances (e.g., sodium, potassium, sulfate, and chloride) at a ton scale. Chemical precipitation is mostly used for phosphate removal. In this study, a biotechnological process utilizing Saccharomyces cerevisiae to upcycle phosphate-containing wastewater into pure sodium polyphosphate in powder form was developed. The process comprises fermentation and downstream processing (polyphosphate yields: 25% and 36%, respectively). The polyphosphate quality was independent of the wash water composition. Polyphosphate with a purity of 23% molar ratio Na to Na, K, and Mg of > 90%, and with an average chain length of 12.5 phosphate subunits was produced. The upcycled polyphosphate can be reused compared to phosphate fertilizer in many different applications. Overall, the here developed process can contribute to truly slowing down phosphate mining and finally enable a sustainable utilization of phosphate. Thereby, the benefit of the process is the cascade use of phosphate, reducing the need for phosphate rock before the phosphate ends up in the soil and ultimately in the sea., (© 2022 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals LLC.)

Inorganic polyphosphate (polyP) is the polymer of phosphate. Water-soluble polyPs with average chain lengths of 2-40 P-subunits are widely used as food additives and are currently synthesized chemically. An environmentally friendly highly scalable process to biosynthesize water-soluble food-grade polyP in powder form (termed bio-polyP) is presented in this study. After incubation in a phosphate-free medium, generally regarded as safe wild-type baker's yeast (Saccharomyces cerevisiae) took up phosphate and intracellularly polymerized it into 26.5% polyP (as KPO 3 , in cell dry weight). The cells were lyzed by freeze-thawing and gentle heat treatment (10 min, 70°C). Protein and nucleic acid were removed from the soluble cell components by precipitation with 50 mM HCl. Two chain length fractions (42 and 11P-subunits average polyP chain length, purity on a par with chemically produced polyP) were obtained by fractional polyP precipitation (Fraction 1 was precipitated with 100 mM NaCl and 0.15 vol ethanol, and Fraction 2 with 1 final vol ethanol), drying, and milling. The physicochemical properties of bio-polyP were analyzed with an enzyme assay, 31 P nuclear magnetic resonance spectroscopy, and polyacrylamide gel electrophoresis, among others. An envisaged application of the process is phosphate recycling from waste streams into high-value bio-polyP., (© 2020 The Authors. Biotechnology and Bioengineering published by Wiley Periodicals, Inc.)

Due to the limited solubility of phosphorus (P) in soil, understanding its binding in fine colloids is vital to better forecast P dynamics and losses in agricultural systems. We hypothesized that water-dispersible P is present as nanoparticles and that iron (Fe) plays a crucial role for P binding to these nanoparticles. To test this, we isolated water-dispersible fine colloids (WDFC) from an arable topsoil (Haplic Luvisol, Germany) and assessed colloidal P forms after asymmetric flow field-flow fractionation coupled with ultraviolet and an inductively coupled plasma mass spectrometer, with and without removal of amorphous and crystalline Fe oxides using oxalate and dithionite, respectively. We found that fine colloidal P was present in two dominant sizes: (i) in associations of organic matter and amorphous Fe (Al) oxides in nanoparticles <20 nm, and (ii) in aggregates of fine clay, organic matter and Fe oxides (more crystalline Fe oxides) with a mean diameter of 170 to 225 nm. Solution P-nuclear magnetic resonance spectra indicated that the organically bound P predominantly comprised orthophosphate-monoesters. Approximately 65% of P in the WDFC was liberated after the removal of Fe oxides (especially amorphous Fe oxides). The remaining P was bound to larger-sized WDFC particles and Fe bearing phyllosilicate minerals. Intriguingly, the removal of Fe by dithionite resulted in a disaggregation of the nanoparticles, evident in higher portions of organically bound P in the <20 nm nanoparticle fraction, and a widening of size distribution pattern in larger-sized WDFC fraction. We conclude that the crystalline Fe oxides contributed to soil P sequestration by (i) acting as cementing agents contributing to soil fine colloid aggregation, and (ii) binding not only inorganic but also organic P in larger soil WDFC particles., (Copyright © by the American Society of Agronomy, Crop Science Society of America, and Soil Science Society of America, Inc.)