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

Abstract

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 CO 2 and light, followed by anaerobic H 2 production in the absence of light and sulfur. M. aeruginosa was capable of generating H 2 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 H 2 production rates, total produced volume and the lag time required for cell adaptation prior to H 2 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 H 2 production, at least two days of photosynthesis under conditions with light, CO 2, and sulfur should be allowed for cells to recover H 2 production potential and cell viability.