Biofilm-based photobioreactor absorbing water and nutrients by capillary action

Cells of the unicellular green alga, "Pseudochoricystis ellipsoidea", were uniformly spread on a cellulosic sheet or on a polytetrafluoroethylene (PTFE) membrane sheet superimposed on a cellulosic sheet at a density of 3.5-5.0gdry weight per m², and the sheet was adhered to an inverted V-shaped acrylic plate of 10cm in height. Several acrylic plates were placed side by side on a tray containing liquid medium at a depth of 0.6cm, and illuminated from above with a light intensity of 300-340μmolm^-2s^-1. Water and nutrients were supplied to cells by capillary action through the cellulosic sheet. Footprint biomass productivities of cells grown in atmospheric CO₂ on this photobioreactor were 8-10gm^-2day^-1. This cultivation system is strongly energy- and labor-saving as it does not require mixing of culture fluid, irrigation of medium, and delivery of CO₂-enriched air.