Microbial hydrogen production from phenol in a two-step biological process

• A two-step process to efficiently convert phenol to H2 is proposed and demonstrated.
• In the first step phenol was converted to benzoate by mixed anaerobic cultures in an acidogenic reactor.
• The formed benzoate was further fermented to H2 by Rhodopseudomonas palustris.

Phenol biodegradation is usually limited by a low treatment efficiency due to the microbial inhibition with intermediate accumulation. In this study, we report a two-step process to efficiently convert phenol to H2. In the first step, phenol was converted to benzoate by mixed anaerobic cultures in an acidogenic reactor; subsequently, the formed benzoate was further fermented to H2 by Rhodopseudomonas palustris, an efficient photosynthetic bacterium. The individual steps were simulated by mathematical models. The modified Gompertz model was used to describe the H2 production process from benzoate by R. palustris. The results show that the effluent from the acidogenic reactor treating phenol could be directly used by R. palustris for H2 production. The maximum H2 production rate was estimated to be 0.545 mL/h. The H2 yield and light conversion efficiency were 0.58 and 2.08%, respectively. The results of this study suggest that such a two-step process can efficiently degrade aromatic compounds like phenol with concurrent H2 production.

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