Improved hydrogen production with expression of hemH and lba genes in chloroplast of Chlamydomonas reinhardtii

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.