Sustained photobiological hydrogen production by Chlorella vulgaris without nutrient starvation

Abstract

This article describes the ability of the Chlorella vulgaris BEIJ strain G-120 to produce hydrogen (H2) via both direct and indirect pathways without the use of nutrient starvation. Photobiological H2 production reached a maximum rate of 12 mL H2 L1 h1 , corresponding to a light conversion efficiency (light to H2) of 7.7% (average 3.2%, over the 8-day period) of PAR, (photosynthetically active irradiance). Cells presented a maximum in vivo hydrogenase activity of 25.5 ± 0.2 nmoles H2 mgChl1 h1 and the calculated in vitro hydrogenase activity was 830 ± 61 nmoles H2 mgChl1 h1 . The strain is able to grow either heterotrophically or photo autotrophically. The total output of 896 mL of H2 was attained for illuminated culture and 405 mL for dark cultures. The average H2 production rate was 4.98 mL L1 h1 for the illuminated culture and 2.08 mL L1 h1 for the one maintained in the dark.