Spiral tubular bioreactors for hydrogen production by photosynthetic microorganisms - Design and operation

Spiral tubular bioreactors were constructed out of transparent PVC tubing for H-2 production applications. Both a cyanobacterial Anabaena variabilis mutant that lacks uptake hydrogenase activity and the photosynthetic bacterium Rhodobacter sp. CBS were tested in the bioreactors. Continuous H-2 photoproduction at an average rate of 19 mL . min(-2) . h(-1) was observed using the A. variabilis mutant under an air atmosphere (without argon sparging or application of a partial vacuum). The cyanobacterial photobioreactor was run continuously for over one month with an average efficiency of light energy conversion to H-2 of 1.4%. Another H-2-producing approach employed a unique type of activity found in a strain of photosynthetic bacteria that shifts CO (and H2O) into H-2 (and CO2) in darkness. Continuous dark H-2 production by Rhodobacter sp. CBS from CO (in anticipation of using synthesis gas as the future substrate) at rates up to 140 mL . g cdw(-1) . h(-1) was observed in a bubble-train bioreactor for more than 10 d.