Optimization of molecular hydrogen production by Rhodobacter sphaeroides O.U.001 in the annular photobioreactor using response surface methodology

Photofermentative H2 production at higher rate is desired to make H2 viable as cheap energy carrier. The process is influenced by C/N composition, pH levels, temperature, light intensity etc. In this study, Rhodobacter sphaeroides strain O.U 001 was used in the annular photobioreactor with working volume 1 L, initial pH of 6.7 ± 0.2, inoculum age 36 h, inoculum volume 10% (v/v), 250 rpm stirring and light intensity of 15 ± 1.1 W m−2. The effect of parameters, i.e. variation in concentration of DL malic acid, L glutamic acid and temperature on the H2 production was noted using three factor three level full factorial designs. Surface and contour plots of the regression models revealed optimum H2 production rate of 7.97 mL H2 L−1 h−1 at 32 °C with 2.012 g L−1 DL malic acid and 0.297 g L−1 L glutamic acid, which showed an excellent correlation (99.36%) with experimental H2 production rate of 7.92 mL H2 L−1 h−1.