Characteristics of hydrogen production by immobilized cyanobacterium Microcystis aeruginosa through cycles of photosynthesis and anaerobic incubation

The characteristics of hydrogen production using immobilized cyanobacterium Microcystis aeruginosa were studied through a two-stage cyclic process. Immobilized cells were first grown photosynthetically under CO2 and light, followed by anaerobic H2 production in the absence of light and sulfur. M. aeruginosa was capable of generating H2 under immobilized conditions, and the use of immobilized cells allowed the maintenance of stable production and sped up the changes in culture conditions for cyclic two-stage operation. M. aeruginosa was also capable of utilizing exogenous glucose as a substrate to generate hydrogen and 30 mM concentration proved to be optimal. The externally added glucose improved H2 production rates, total produced volume and the lag time required for cell adaptation prior to H2 evolution. The rate of hydrogen evolution was increased as temperature increased, and the maximum evolution rate was 48 mL/h/L and 34.0 mL/h/L at 42 °C and 37 °C, respectively. The optimal temperature for hydrogen production was 37–40 °C because temperatures higher than 42 °C resulted in cell death. In order to continue repeated cycles of H2 production, at least two days of photosynthesis under conditions with light, CO2, and sulfur should be allowed for cells to recover H2 production potential and cell viability.