Improved phosphate biosorption by bacterial surface display of phosphate-binding protein utilizing ice nucleation protein

Abstract

The conventional enhanced biological phosphorus removal (EBPR) system often deteriorates at low chemical oxygen demand (COD) or under aeration conditions. A new approach that incorporates phosphate-eutrophic wastewater remediation was introduced through immobilization of an intracellular phosphate-binding protein (PBP) onto the surface of Pseudomonas putida or Escherichia coli, using the N-terminal anchor (InaQ-N) of a newly identified ice nucleation protein from Pseudomonas syringae. A green fluorescent protein-fusion protein was expressed and used to confirm surface localization. The PBP was then targeted to the surface of E. coli JM109 and P. putida AB92019. The engineered P. putida and E. coli microorganisms were capable of absolute biosorption of total phosphates at rates of 60 and 80 mg L(-1), respectively, over 5 h. In the recombinant P. putida cells, a surface-immobilized PBP fusion that had three tandemly repeated InaQ-Ns exhibited the maximum increment in phosphate biosorption, at sixfold compared with the control strain. Even heat-killed recombinant cells of either P. putida or E. coli retained substantial biosorptive activities. The current study demonstrates that the bacterial surface display of PBP should be considered as a strong contender for generating organisms capable of functioning in EBPR systems under low COD, resulting in improved removal of eutrophic phosphorus from wastewaters.