Enhanced hydrogen production by controlling light intensity in sulfur-deprived Chlamydomonas reinhardtii culture

Chlamydomonas reinhardtii is a green alga that can use light energy to produce hydrogen from water under anaerobic conditions. This work reports the enhancement of hydrogen production by controlling the light intensity in sulfur-deprived anaerobic C. reinhardtii cultures. The overall hydrogen production was dependent on light intensity in the range of 60– 200 μ E m - 2 s - 1 . Maximum hydrogen production was obtained at a light intensity of 200 μ E m - 2 s - 1 as a result of the rapid initiation of hydrogen production and the greatest increase of chlorophyll during the initial 24 h after sulfur deprivation. However, the hydrogen production was inhibited at an intensity of 300 μ E m - 2 s - 1 of light owing to photosystem II photodamage by excess light. The maximum hydrogen production and the maximum specific production rate of hydrogen were 225 ml H 2 l - 1 culture and 2.01 ml H 2 g - 1 cells h - 1 , respectively. Thus, hydrogen production by sulfur-deprived C. reinhardtii cultures can be maximized by controlling the light intensity at levels below saturation.