Hydrogen and poly-β-hydroxybutyric acid production at various acetate concentrations using Rhodobacter capsulatus DSM 1710

In the present study, Rhodobacter capsulatus DSM 1710 was cultured in media having various concentrations of acetate (10–65 mM) to investigate simultaneous production of hydrogen and PHB. The highest cumulative hydrogen productions were observed using 50 mM (11.7 mmol H2) and 65 mM (11.4 mmol H2) acetate. However, molar productivity values were higher at 25 mM (0.50 mmol/Lc.h) and 50 mM (0.44 mmol/Lc.h) compared to 65 mM (0.35 mmol/Lc.h). Furthermore, the highest PHB production (234.7 mg/L) was attained using 65 mM acetate. At molecular level, the expressions of nifD and phaC genes were analyzed by reverse transcription-polymerase chain reaction using specifically designed tagged primers. Increasing acetate concentrations resulted in an increase in nifD and phaC expressions. Accordingly, the highest transcription levels were obtained at 65 mM acetate. The kinetic studies on hydrogen production and acetate consumption showed that hydrogen production data was in agreement with the Modified Gompertz Model and acetate was consumed through first order kinetics.