Effect of light intensity and light pattern on hydrogen production by unicellular green alga chlorella sp. LSD-W2

Abstract

Green microalgae can use solar energy and water to produce H2 via hydrogenase enzyme activity. The unicellular green alga Chlorella sp. LSD-W2 has been previously shown to produce high H2 under nitrogen deprivation. This research aimed to examine the effects of light intensity and light pattern on H2 production by Chlorella sp. LSD-W2 under nitrogen deprivation. The result showed that H2 production rate was significantly enhanced when light intensities were increased. The cells could hardly produce H2 in the dark. The highest H2 production rate with 0.956 ± 0.015 mL L-1 h-1 was obtained in cells incubated in TAP-N medium in a 120-mL glass bottle under light intensity of 60 μmol photons m-2 s-1. H2 production by cells incubated under light/dark or dark/light cycles was lower than that under continuous light illumination. In order to reduce O2 which is an inhibitor of hydrogenase enzyme, the PSII inhibitor, 3-(3,4-dichlorophenyl)-1,1-dimethylurea (DCMU) was added to the Chlorella sp. LSD-W2 cell cultures. It was found that O2 was obviously decreased in cells treated with 10 μM DCMU. Unexpectedly, DCMU caused the reduction of H2 production by Chlorella sp. LSD-W2.