The performance of ordinary bioreactors, i.e. those that handle a three-phase system consisting of gas (O 2 in/exhaust gas out), liquid (medium) and solid (biocatalyst), is defined by the mixing time/energy input required per reactor volume for a growth-limiting substrate and the resulting productivity in g/L reactor volume *t ime .In photobioreactors, the reactor performance depends on a fourth phase, light (i.e. a g, l, l, s system). In solely autotrophic systems, light has to be the only "productivity limiting substrate" for microalgae upgrowth. To achieve high productivities, all the sunlight available under any actual weather condition has to be converted into biomass energy. Since the solar intensity underlies seasonal and diurnal variances between 50 and 2,000 microeinstein per m 2 *sec, problems with both photolimitation and photoinhibition may arise.The only way to overcome these is turbulence, which must be used to avoid limiting (transport of microalgae to light) and inhibitive ("light dilution") light conditions. Subitec's ideally mixed flat-panel-airlift system (FPA) is able to convert all naturally occurring light conditions at its best by adapted turbulence, i.e. adapted light dilution at given microalgae concentrations inside the reactor. Therefore, high productivities at high biomass concentrations within the reactor can be stably realized under quasi-continuous conditions using the FPA system.
Subitec GmbH and the flat-panel-airlift systemSubitec GmbH, situated in Stuttgart, Germany, was founded in 2000 as a spinoff of the Fraunhofer Institute for Interfacial Engineering and Biotechnology (IGB, Stuttgart, Germany). Subitec GmbH acquired two globally granted patent families regarding the design and the manufacturing process of the novel FPA photobioreactor system being incessantly refined, i.e. in terms of alternative materials, fluid dynamics and automation. In order to produce microalgae biomass with FPA reactors, Subitec GmbH developed integrated circulation processes: the CO 2 needed to cultivate the algae is derived from industrial processes, i.e. flue gases from power plants. The closed system allows circulation of water and nutrients, and the con-Brought to you by | New York University Bobst Library Technical Services Authenticated Download Date | 2/6/15 2:05 AM