BIOLOGICAL HYDROGEN FROM FUEL GASES

Upon adding CO to the gas phase of the photosynthetic bacterium Rubrivivax gelatinosus CBS, a CO oxidation: H2 production water-gas shift pathway is induced. Based on chloramphenicol inhibition studies, CO induces the de novo synthesis of new proteins in the CO shift pathway. When various amounts of CO were added during sub-culturing, a minimal level of 10 % (v/v) is required for the maximal induction of the CO shift activity. Daily feeding of 20 % CO also prolongs the CO shift activity at a higher and constant rate versus a culture fed with CO only during inoculation. After screening a library of transposon mutants, we identified two lines deficient in CO shift activity. Biochemical analysis indicated that mutant GV1214 lacks carbon monoxide dehydrogenase (CODH) activity and mutant GV 1762 lacks hydrogenase activity. Sequence analysis suggests that the mutations occurred in a CODH gene and hydrogenase large subunit gene, respectively. The physiological and molecular biology studies provide insight into the biological CO shift pathway and have significance in producing additional H2 from gasified waste biomass