Renewable Phytase Biocatalyst to Transform Biorefinery Waste Streams into Phosphorus Resources

Phosphorus (P) recovery is crucial for sustaining the global food supply and preventing freshwater pollution. Biorefinery waste streams have emerged as promising, yet underexplored sources for P recovery. Here, we presented a renewable and robust cell surface-displayed Escherichia coli phytase (SDEcP) biocatalyst to convert organic P into inorganic P, thereby facilitating efficient phosphate recovery from biorefinery waste. This biocatalyst exhibited high enzyme activity (137.6 ± 3.7 U per gram of dry cell weight), maximal phosphate production rate of 75.3 ± 2.3 μM min^-1, consistent full activity after 36 days, and simple regeneration via cell cultivation. We leveraged a machine learning-based approach to obtain SDEcP variants with up to 55% increase in enzyme activity and robustness for phytate conversion from real-world light steepwater. Selective phosphate recovery from SDEcP-treated steepwater was achieved by using agarose beads functionalized with phosphate-binding proteins, thus demonstrating a complete waste-to-value pathway. This study advances the development of new biocatalytic approaches for achieving a circular P economy.