Biohydrogen production by immobilized Chlorella sp. using cycles of oxygenic photosynthesis and anaerobiosis

Abstract

Hydrogen production was studied using immobilized green alga Chlorella sp. through a two-stage cyclic process where immobilized cells were first incubated in oxygenic photosynthesis followed by anaerobic incubation for H 2 production in the absence of sulfur. Chlorella sp. used in this study was capable of generating H 2 under immobilized state in agar. The externally added glucose enhanced H 2 production rates and total produced volume while shortened 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 under 30 mM glucose was 183 mL/h/L and 238 mL/h/L at 37 °C and 40 °C, respectively. In order to continue repeated cycles of H 2 production, at least two days of photosynthesis stage should be allowed for cells to recover H 2 production potential and cell viability before returning to H 2 production stage again.