Photo-Biological Hydrogen Production by the Uptakehydrogenase and PHB Synthase Deficient Mutant of Rhodobacter Sphaeroides

Abstract

Among various hydrogen (H2) production technologies, biological conversion to H2 has received more attention as a sustainable technology because organic wastes, water, and various gases are cheaper starting materials. Photobiological H2 production by purple non-sulfur bacteria is one of the most promising methods under photoheterotrophic conditions. The highest rate of photobiological H2 production has been achieved with strains belonging to the purple non-sulfur bacteria Rhodospirillaceae, and this method also accumulates useful by-products in addition to H2. This chapter discusses a study that examined a newly isolated Rhodobacter sphaeroides (Rb. spaeroides) KD131 strain and a mutant derived from Rb. spaeroides KD131 by internal deletion of Hup SL and Phb C genes on their properties of growth and H2 evolution using different substrates and under different culture conditions. Both strains produced H2 beginning from the middle of the logarithmic growth phase and continued until the cell concentration leveled out. The rates of H2 production were 1.62 ml H2/ml-broth for the wild-type strain and 2.2 ml H2/ml-broth for the mutant strain in 48 hr under the irradiance of 8 klux/m2 using halogen lamps in the broth containing 30 mM D, L-malate, and 8mM L-glutamate as carbon and nitrogen sources, respectively.