Hydrogen photo-evolution by Rhodopseudomonas palustris 6A using pre-treated olive mill wastewater and a synthetic medium containing sugars

Increasing costs of petroleum, associated with the escalating problems of global climate change, require always greater efforts in order to produce an energy carrier as bioH2. In this study, bioH2 production using photofermentative process was investigated. Two culture broths were used: (a) a synthetic medium rich in sugars (glucose and fructose) and (b) a pre-treated fresh olive-mill wastewater (OMWF) diluted with water (30%, v:v). The pre-treatment was carried out using two different vegetable matrices (dry-Azolla and granular active carbon) to decrease both the content of polyphenols and the dark colour of wastewater. Rhodopseudomonas palustris 6A isolated from soil spread with OMW was utilized for batch growth experiments, carried out indoors under continuous light (200 μE/m2/s). When synthetic medium was used, the culture mixing was performed using either (i) a magnetic stir bar, and (ii) an impeller equipped with five turbines. The latter system made it possible to increase the bioH2 photo-evolution by 1.4 times. The specific hydrogen photo-evolution rate was 13.5 mL/g(dw)/h in the broth containing diluted OMWF and 11.8 mL/g(dw)/h in the synthetic medium containing sugars (glucose and fructose).