Feasibility studies for a photosynthetic artificial lung. Optimization of parameters affecting photosynthesis

As an alternative to conventional extracorporeal membrane oxygenation (ECMO) hardware, preliminary studies were conducted toward the development of a life support system based on biologic processes for the direct generation of O2 and removal of CO2 by the action of a photosynthetic organism. A high temperature strain of Chlorella pyrenoidosa, which functions optimally at 37 degrees C and pH 7.4, was cultured in a 3 I fermenter with artificial lighting provided with Hg-metal halide lights. The pH, total CO2 and partial pressure of oxygen (PO2) of the system were monitored at regular intervals using flow-through microelectrodes. The degree of importance of light intensity, substrate concentration, and cell density in the photosynthetic ability of Chlorella in batch culture were assessed over a 2 hour period. At high light intensities, the O2 production, CO2 removal, and pH changes were significantly greater than those at low irradiance levels. Over the range of HCO3- concentrations used in these experiments, the initial HCO3- levels did not appear to have a significant effect on the rates of O2 production/CO2 removal. The total amount of O2 produced/CO2 removed and pH changes were found to be greater with higher cell densities. Under more optimal culture conditions, it may be feasible to eventually interface this photobioreactor with blood across a semipermeable membrane and catalytically convert blood CO2 to O2 directly, needing only an adequate light source.