A reversible physiological process provides for the temporal separation of oxygen evolution and hydrogen production in a microorganism, which includes the steps of growing a culture of the microorganism in medium under illuminated conditions to accumulate an endogenous substrate, depleting from the medium a nutrient selected from the group consisting of sulfur, iron, and/or manganese, sealing the culture from atmospheric oxygen, incubating the culture in light whereby a rate of light-induced oxygen production is equal to or less than a rate of respiration, and collecting an evolved gas. The process is particularly useful to accomplish a sustained photobiological hydrogen gas production in cultures of microorganisms, such as Chlamydomonas reinhardtii.
CONTRACTUAL ORIGIN OF THE INVENTION
The United States Government has rights in this invention pursuant to Contract No. DE-AC36-99-GO10337 between the United States Department of Energy and the Midwest Research Institute and pursuant to Contract No. DE-FC36-98 G0010278 between the United States Department of Energy and the University of California at Berkley.