Optimization of H2 photo-fermentation from benzoate by Rhodopseudomonas palustris using a desirability function approach

Abstract

The operational conditions of H2 production from benzoate by Rhodopseudomonas palustris was optimized in batch experiments by using the response surface methodology (RSM) and a desirability function approach. The estimated best H2 production performance, i.e., maximum substrate-to-hydrogen conversion efficiency of 0.61 and light conversion efficiency of 3.20%, was achieved at: benzoate concentration 9.97 mM, NH4Cl concentration 0.21 g/L and pH 6.76. These parameters were employed for running a continuous H2 production bioreactor, for which the optimal hydraulic retention time was found to be 6 d. Under a light–dark cycle, R. palustris survived and maintained their H2 production activity in the continuous operating system. The results demonstrate that it is possible to operate an outdoor photo-bioreacror for continuous H2 production by utilizing aromatic compound as substrate. This works offer implications for guiding the design and operation of more energy–productive processes for treatment of aromatic compound-containing wastewater treatment.