Influence of Different Substrate and Microorganism Concentrations on Butyric Acid-Derived Biohydrogen Production

This study examines the effect of inoculum (0.5–3 g/L) and substrate concentration (40–200 g/L) on butyric acid and biohydrogen production by batch dark fermentation at 37 °C. Clostridium pasteurianum DSM525 and Cheese Whey Powder (CWP) were used in the experiments. The results showed that biohydrogen and butyric acid production increased with a 1.5 g/L microorganism concentration and 80 g/L CWP. A Cumulative Hydrogen Formation (CHF) of 458 mL, butyric acid (BA) of 1.523 g/L, butyric acid to acetic acid (BA/AA) ratio of 3.07 g BA/g AA, hydrogen production yield (YH2/TS) of 1278.63 mL H2/g TS, and butyric acid production yield (YBA/TS) of 0.37 g BA/g TS at 1.5 g/L inoculum concentration was achieved. The hydrogen (HPR) and butyric acid production rates (BAPR) were similarly the highest at 1.5 g/L. The maximum specific hydrogen (SHPR) and butyric acid rates (SBAPR) were obtained at 2 g/L and 1 g/L organism concentrations, respectively. In variations of substrate concentrations, 651.1 mL of CHF, 1.1 g/L of BA, 3.23 g BA/g AA of BA/AA ratio, 576 mL H2/g TS of YH2/TS, and 27.4 g BA/g TS of YBA/TS were accomplished. HPR and SHPR were the highest at 80 g/L CWP due to no substrate inhibition. The BAPR was at its maximum at 100 g/L, BA accumulation was faster, and the SBAPR was at maximum 40 g/L CWP. The results showed a good adaptation of C. pasteurianum to the butyric acid-derived hydrogen production pathway. This strategy could build a renewable and sustainable process with dual valuable outputs.