Feasibility study on bioreactor strategies for enhanced photohydrogen production from Rhodopseudomonas palustris WP3-5 using optical-fiber-assisted illumination systems

A novel photobioreactor (PBR) was utilized to produce H2 by indigenous purple nonsulfur bacterium Rhodopseudomonas palustris WP3-5 using acetate as the sole carbon source. The PBR was illuminated by combinative light sources including side-light optical fibers (internal light source) as well as external irradiation of halogen lamp and/or tungsten filament lamp. A fill and draw (F/D) operation of PBR was shown to improve the performance of photoH2 production over the performance of batch and continuous cultures under similar operation conditions. For medium improvement, the PBR was conducted under different concentrations of carbon source (acetate) and nitrogen source (glutamic acid). The results show that the highest overall H2 production rate (vH2)(vH2) and H2 yield (YH2)(YH2) occurred when the acetate concentration was 32.5 mmol/l and the glutamic acid concentration was 400 mg/l. The optimal acetate and glutamic acid concentration led to a vH2vH2 and YH2YH2 of 20.9 ml/h l and 2.47 mol H2/mol acetate, respectively. The H2 production rate and yield was further enhanced to as high as 38.2 ml/h l and 3.15 mol H2/mol acetate, respectively, while using a ternary-light-source (TLS) system, combining optical fiber, halogen lamp, and tungsten filament lamp (i.e., the OF/HL/TL system). Meanwhile, the high H2 production efficiency with TLS system was stably maintained for nearly 30 day under the F/D operations.