High yield single stage conversion of glucose to hydrogen by photofermentation with continuous cultures of Rhodobacter capsulatus JP91

Photofermentative hydrogen (H2) production from glucose with the photosynthetic bacterium Rhodobacter capsulatus JP91 (hup−) was examined using a photobioreactor operated in continuous mode. Stable and high hydrogen yields on glucose were obtained at three different retention times (HRTs; 24, 48 and 72 h). The H2 production rates, varying between 0.57 and 0.81 mmol/h, and optical densities (OD600nm) were similar for the different HRTs examined. However, the rate of glucose consumption was influenced by HRT being greater at HRT 24 h than HRTs 48 and 72 h. The highest hydrogen yield, 9.0 ± 1.2 mol H2/mol glucose, was obtained at 48 h HRT. These results show that single stage photofermentative hydrogen production from glucose using photobioreactors operated in continuous culture mode gives high, nearly stoichiometric yields of hydrogen from glucose, and thus is considerably more promising than either two stage photofermentation or co-culture approaches.