Nitrate removal by immobilized cells of Phormidium uncinatum in batch culture and a continuous-flow photobioreactor
Gil, J.; Serra, J.
Applied microbiology and biotechnology 39(6): 782-787
Cells of the non-N2-fixing cyanobacterium Phormidium uncinatum were immobilized by adsorption into polyvinyl (PV-50) foam pieces. The effect of inoculum size as well as the initial inoculum/support ratio on the cell immobilization process was investigated. After 2 months of immobilization similar net O2-exchange activity was measured in immobilized and free-living cells. Polyvinyl-adsorbed cells also showed similar nitrate uptake capacity to free-living cells. Nitrogen starvation promoted a remarkable increase in nitrate uptake rate of both free-living and immobilized cells. A lab-scale photobioreactor packed with polyvinyl foam pieces colonized in situ by cells was used for nitrate removal in a continuous mode. In the best working conditions found, nearly 90% of nitrate supplied in the influent (50 mg l(-1)) was removed by cells having a residence time of 3-4 h.