Abstract

Hydrogen (H2) is a promising clean energy carrier that can be produced from green algae. By screening H2-producing Chlorella species, Chlorella sp. ChiW1, isolated from a rice paddy field in Chai Nat province, Thailand, exhibited the highest H2 production rate and yield. The mid-logarithmic phase cells of Chlorella sp. ChiW1 demonstrated the highest H2 production. Nitrogen deprivation doubled the H2 production compared to normal conditions, due to increased hydrogenase activity resulting from reduced O2 evolution. Furthermore, a high concentration of acetic acid in Tris-acetate phosphate medium, combined with increased light intensity, significantly enhanced H2 production. Under optimal conditions, nitrogen-deprived Chlorella sp. ChiW achieved a maximum H2 production rate of 31.28 ± 1.73 μmol H2 mg chl−1 h−1 and a total H2 production yield of 925.32 ± 19.95 μmol H2 mg chl−1 after 96 hours of light anaerobic incubation. Compared to other reported Chlorella strains, Chlorella sp. ChiW exhibited significantly higher H2 production, underscoring its potential for efficient biohydrogen production.

Key words: H2 production, Chlorella, nitrogen deprivation