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 degrees C and 40 degrees 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. (C) 2011 Elsevier Ltd. All rights reserved.