USE OF LEVULINIC ACID BY RHODOPSEUDOMONAS SP NO-7 FOR PHOTOTROPHIC GROWTH AND ENHANCED HYDROGEN EVOLUTION

A purple nonsulfur bacterium, Rhodopseudomonas sp. No. 7, grew well in a salt medium containing levulinic acid (LA) as a source of carbon an d an electron donor. When strain No. 7 was incubated in a medium conta ining glutamate as a nitrogen source, it continued to evolve hydrogen from 20 mM LA for about 200 h with a yield of hydrogen of more than 75 %. The consumption of LA by resting cells was strongly dependent on li ght. The level of 5-aminolevulinic acid dehydratase (EC 4.2.1.24) in c ells grown in the LA-medium increased about 2 to 5 times over that of cells grown in LA-free media. However, about 50% inhibition of the enz yme activity in cell-free extracts prepared from these cells was obser ved in the presence of 5 mM LA regardless of growth conditions. Rhodop seudomonas palustris and Rhodopseudomonas acidophila could use LA for growth like strain No. 7, but Rhodopseudomonas blastica, Rhodospirillu m rubrum, Rhodobacter sphaeroides, Rubrivivax gelatinosus, and Rhodocy clus tenuis could not.