Axenic cultivation of anoxygenic phototrophic bacteria, cyanobacteria, andmicroalgae in a new closed tubular glass photobioreactor

A low-cost closed tubular glass photobioreactor allowing axenic cultivation of phototrophic microorganisms was constructed. Standard glass tubes were arranged in a helical array providing a working volume of 80 1. The glass t ubes were connected with a degassing chamber, which also provided ports for measuring and regulating oxygen supply, pH, foam, and optical density and for adding substrates and antifoam agents as well as disposing of vent gas. A pump module allowed agitation of the medium in the bioreactor at a lamin ar flow rate of 1.5 m/s. Upstream of the pump module a gas inlet was locate d, allowing efficient mixing of the used gases with the medium. The tempera ture of the medium was controlled by a Pt-100 sensor and by a heat exchange r with an effective surface of 0.12 m(2) connected to an external thermosta t. Irradiation was provided by three light panels each consisting of ten fl uorescent tubes. The entire photobioreactor - apart from the light panels a nd motor - could be sterilized at 121 degrees C in an autoclave. In additio n to a detailed description of this photobioreactor, we report on first exp eriments to cultivate the anoxygenic phototrophic bacteria Rhodobacter spha eroides and Rhodospirillum rubrum, the oxygenic phototrophic cyanobacterium Synechocystis sp. strain PCC6803, and the microalga Chlorella sp. in this photobioreactor.