Poly(3-hydroxybutyrate) as an endogeneous substrate for H 2 evolution in Rhodovulum sulfidophilum

Abstract

In the absence of an external substrate, H 2 was evolved in Rhodovulum sulfidophilum under light-anaerobic conditions, along with degradation of poly(3-hydroxybutyrate) (PHB). Cells grown with succinate as a sole carbon source accumulated only a small amount of PHB compared with that in cells grown with a multiple substrate consisting of a mixture of four organic acids. Unlike PHB-containing cells, PHB-deficient cells did not evolve H in the absence of an external substrate. Nitrogenase activity was expressed while no hydrogenase activity was detected during the incubation of PHB-containing cells. These results suggest that intracellular PHB serves as a substrate for the H evolution catalyzed by nitrogenase when an external substrate is lacking.