Surfactant-Induced hydrogen production in cyanobacteria

Addition of Tween 85 to aqueous suspensions of Anabaena variabilis induced photosynthetic evolution of hydrogen over a time span of several weeks: As much as 148 nmol H(2)/h . mg dry weight was produced in the first week by a suspension containing 4.2 mg dry weight of cells and 77 mM Tween 85. The chemical structure of Tween 85 was a necessary prerequisite for inducing hydrogen production, as compounds such as Tween 20, 60, and 80 had a quite different effect. There was a coupling between photosynthetic oxygen evolution and hydrogen evolution: Hydrogen evolution started to be effective only when oxygen evolution subdued. The presence of heterocysts in A. variabilis was also required for the Tween-induced hydrogen production. Based on these observations, possible mechanisms for the photosynthetic effect of Tween 85 are advanced and discussed.