Spiral tubular bioreactors for hydrogen production by photosynthetic microorganisms : design and operation

Spiral tubular bioreactors were constructed out of transparent PVC tubing for H2 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 H2 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 H2 of 1.4%. Another H2-producing approach employed a unique type of activity found in a strain of photosynthetic bacteria that shifts CO (and H2O) into H2 (and CO2) in darkness. Continuous dark H2 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.