Abstract
With availability of genomic information, it becomes possible to improve photobiological hydrogen productivity by selecting target genes and genetically modifying them based on scientific information about photosynthesis, biochemistry of enzymes and metabolism, and molecular biology. Anabaena PCC 7120 can produce hydrogen as an inevitable by-product of nitrogenase reaction. In order to decrease reabsorption of hydrogen, we created three hydrogenase mutants (ΔhupL, ΔhoxH, ΔhupL/ΔhoxH) and showed that the ΔhupL and ΔhupL/ΔhoxH produced hydrogen at a rate 4-7 times that of wild-type. However, the high activity stage lasts for only about 10 hours. Homocitrate is liganded to the catalytic cluster of nitrogenase, and in other microorganisms inactivation of its synthase decreases efficiency of nitrogen fixation leading to increased hydrogen production. We have created three homocitrate synthase gene disruptants (ΔnifV1, ΔnifV2, ΔnifV1/ΔnifV2) on the ΔhupL background. Some of the mutants show higher and more lasting hydrogen productivity.
