Phosphate removal and recovery using immobilized phosphate binding proteins

Area of Science:

• Environmental Science
• Biotechnology
• Water Treatment Technologies

Background:

• Achieving a circular phosphorus economy requires advanced water treatment systems capable of reversibly removing inorganic phosphate (Pi) to very low concentrations (<100 μg L⁻¹).
• Current methods often lack efficiency in both removal and subsequent recovery of phosphate for reuse.
• The development of novel, reusable bio-adsorbents is crucial for sustainable phosphorus management.

Purpose of the Study:

• To investigate the potential of immobilized E. coli phosphate binding protein (PBP) as a reusable bio-adsorbent for inorganic phosphate (Pi).
• To evaluate the efficiency of Pi adsorption and desorption under varying pH and temperature conditions.
• To assess the reusability and stability of the PBP bio-adsorbent over multiple cycles.

Main Methods:

• Expression, extraction, purification, and immobilization of E. coli PBP onto NHS-activated Sepharose beads.
• Adsorption of Pi by PBP beads, followed by desorption studies at various pH (4.7–12.5) and temperatures (25–45 °C).
• Assessment of adsorption/desorption capacity over 10 repeated cycles and thermal stability analysis (thermal shift assay).

Main Results:

• High Pi desorption (62% and 86%) was achieved at alkaline pH 11.4 and 12.5, respectively.
• Pi desorption occurred rapidly (<5 min) and the PBP beads maintained adsorption/desorption capacity over 10 cycles without significant loss.
• Average Pi adsorption was 83% ± 5%, with 89% ± 4.1% desorption at pH 12.5 over 10 cycles; PBP remained structurally stable.

Conclusions:

• Immobilized high-affinity PBP is a promising, effective, and reversible bio-adsorbent for Pi recovery from water and wastewater.
• The PBP bio-adsorbent system demonstrates potential for achieving ultra-low Pi levels and facilitating phosphorus reuse.
• The stability and reusability of PBP beads support their application in sustainable water treatment and circular economy initiatives.