CHAPTER 7: Metabolism and Genetics of Algal Hydrogen Production

Algal hydrogenase research continues to provide important new insights into the origin and function of H₂ metabolism in photoautotrophic microorganisms. Additionally, powerful new genetic tools are emerging to manipulate algae, which when combined with the discovery of promising new enzymes are enabling advanced recombinant techniques with the potential to improve H₂ production in photoautotrophic organisms. In recent years, more O₂-tolerant enzymes have been reported, and “clean” backgrounds that have endogenous hydrogenase activity eliminated in the model organism Chlamydomonas reinhardtii have emerged. Recombinant enzymes are now readily expressed and tested in this system and initial results show promise for improved H₂ production. Several algal genomes/transcriptomes have also recently become available, providing important insights into the evolution and function of native hydrogenases in algae. These efforts suggest an evolutionary relationship among algal hydrogenases that implies a single, ancient incorporation of H₂ metabolism in eukaryotic algae. In summary, the algal hydrogenase field has advanced dramatically in recent years and additional important insights are likely in the coming years.