Study on the Behavior of Production and Uptake of Photobiohydrogen by Photosynthetic Bacterium Rhodobacter sphaeroides RV

Abstract

In this study, using a standard GL system and Roux flask of 1 cm width, the growth rate was saturated at 100 W/m² and the production rate of H₂ increased steadily with light energy from 50–150 W/m². The production of H₂ under halogen lamp illumination (155 W/m²) using a Roux flask of 3 cm width was independent of the initial cell concentration in terms of OD₆₆₀ range 0.18–1.04. The photostationary state of growth was reached at 42 h. Simultaneous consumption of lactate and excretion of organic acids were revealed during the course of H₂ production under standard conditions. Fermentation and CO₂ fixation by Rhodobacter sphaeroides RV was possibly revealed by HPLC analysis of the excreted organic acids during the course of H₂ production and the increase of cell concentration as a result of bacterial growth on CO₂/H₂ (16/84) gas mixture under light (300 W/m²) and dark conditions. These results suggest that the RV strain has an inherent property to perform fermentation while under light conditions, a phenomenon that might lead the way to further investigations aimed at developing an effective strain for wastewater H₂ production process.