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

• Operational conditions of H2 photo-fermentation from benzoate were optimized.
• Response surface methodology and desirability function approach were used.
• Optimized parameters were validated in a continuous H2-producing bioreactor.
• Outdoor photo-bioreactor can apply for H2 production and aromatics degradation.

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.

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