Improvement of nitrogenase-based photobiological hydrogen production by cyanobacteria by gene engineering — Genetic engineering and culture conditions towards improved photobiological hydrogen production by cyanobacteria

Abstract

We are proposing large-scale H2 production on the sea surface utilizing nitrogen-fixing cyanobacteria. Their H2 production activity is based on photosynthesis and nitrogenase activity of the cells. The mutant cells in which the hydrogenase activity had been eliminated by genetic engineering (ΔHup of Nostoc sp. PCC 7422) accumulated H2 for several weeks when N2 concentration was low. For economical H2 production in the future, it was pointed out that the reduction of the cost of the bioreactor is very important. We are proposing a bioreactor composed of several layers of plastic film, with at least one having low permeability to H2. We report here that cyanobacteria culture in a transparent plastic bag produced and accumulated H2 for more than 10 days.