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 H₂ l^{- 1} culture and 2.01 ml H₂ 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.