Short communicationIdentification of negative regulator for phosphate-sensing system in Anabaena sp. PCC 7120: A target gene for developing phosphorus removal

•The ORF all4501 encodes negative regulator for phosphate-sensing system.•Inactivation of all4501 enhanced alkaline phosphatase activity.•Phosphate uptake and cellular phosphorus content were increased in Δall4501 strain.•The Δall4501 strain could remove phosphate from raw RAS water repeatedly.

A negative regulator for phosphate-sensing system in Anabaena sp. PCC 7120 is encoded by all4501. The phosphorus availability and total cellular phosphorus content were enhanced in the Δall4501 strain lacking this negative regulator, while, growth curve was similar to the wild type. The initial rate of phosphate uptake and cellular phosphorus content of the Δall4501 strain were 8-times and 2-times higher than the wild type strain. Increasing of cellular phosphorus content was clearly shown that phosphorus was stored as polyphosphate granules. Phosphorus removal from recirculating aquaculture system using the Anabaena sp. PCC 7120 strain Δall4501 was performed in a 5 L photobioreactor. Separation of treated water and cyanobacterial cells could be achieved spontaneously via simple settle down method. With single starter cell inoculation, the photobioreactor could be repeatedly used for phosphorus removal up to 10 cycles with the average phosphorus removal efficiency of 57.4% and 96.9% for wild type and Δall4501 strains, respectively.