Abstract
The coding region of both the ferrochelatase gene, hemH, from Bradyrhizobium japonicum, and the leghemoglobin gene, lba, from Glycine max, were transferred into chloroplast of Chlamydomonas reinhardtii. As a result, transgenic C. reinhardtii cultures more rapidly consumed O 2 and increased H 2 output compared with controls in both sulfur-free and sulfur-containing medium. H 2 production of the transgenic algal cultures in sulfur-free medium was 4-fold greater than that of control cultures, ∼3.3 ml bottle −1. Maximum expression of the hemH-lba fusion protein on day 5 coincided with the lowest levels of O 2 content and the highest H 2 evolution rate detected over 7 days of anaerobic induction in sulfur-free medium. When the concentration of sulfate in the growth medium was restored to 12.5 or 50 μM, O 2 consumption and H 2 yield decreased more slowly in the transgenic algal cultures than in the control cultures. These results demonstrate that expression of the hemH-lba fusion protein in chloroplast of C. reinhardtii improved their H 2 yield by decreasing O 2 content in the medium, thereby representing the potential for H 2 production in green algae to be improved.
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