Comparison of accumulation by Rhodobacter sphaeroides KD131 and its uptake hydrogenase and PHB synthase deficient mutant

Rhodobacter sphaeroides KD131 and its mutant strain lacking uptake hydrogenase (Hup - ) and PHB synthase (Phb - ) have been studied on H 2 production and cell growth under different culture conditions. Both strains started producing H 2 from the middle of the logarithmic growth phase and continued until the cell concentration leveled out. The rates of H 2 production were 1.32 and 3.34 ml H 2 /mg-dcw for the wild-type and Hup - /Phb - mutant strain, respectively, at the optimum conditions. Malate and lactate were better carbon sources than starch, sucrose or glycerol. Approximately 60% of acetic acid was degraded in 48 h by the wild-type strain and pH increased to 9.4. However, the Hup - /Phb - mutant strain did not grow well and degraded only 19% of acetic acid. The pH ranges of 7.0 were the optimum for the cell growth and pH 7.5 for the H 2 production. Both strains grew and produced hydrogen under the irradiance of 12–120 W/m 2 , but cell growth was inhibited over 400 W/m 2 .