Simultaneous optimization of the hydrogen production rate and substrate conversion efficiency using a response surface methodology

This study investigated the use of the E. coli ATCC8739 strain for biohydrogen production in the dark-fermentation process, and the optimization of the bioprocess using a Box-Behnken design (BBD) and response surface methodology (RSM). The effects of substrate concentration ( S), pH, and temperature (T) on the biohydrogen production rate (R-H2) and substrate conversion efficiency (SCE) were evaluated. The highest R-H2 of 55.32 +/- 5 ml/ l/h was achieved at initial pH (6.58), S (21.08 g/l), and T (36.6 degrees C), with SCE at 90%. Maximum SCE (100%) was obtained at S (11 g/l), pH (7), and T (33 degrees C), while R-H2 was around 47 ml/l/h. Simultaneous optimization of SCE and RH2 was obtained at S (15.2 g/l), pH (6.9), and T (33.5 degrees C), with SCE at 100% and RH2 of 52.64 +/- 5 ml/l/h. The interactive effects of S, pH, and T on R-H2 and SCE were also analyzed. The predicted models of the R-H2 and SCE were in good agreement with the experimental data with an absolute error of 3% and 1%, respectively.