Effect of Substrate pH Value on Hydrogen Production by Photosynthetic Bacteria*

Abstract

For exploring the hydrogen production mechanism of photosynthetic bacteria,hydrogen production by the purple non-sulfur phototrophic bacterium Rhodoseudomonas palustris CQK-01 illuminated by light-emitting diodes with light wavelength of 470 nm was experimentally investigated in batch culture mode under anaerobic conditions,and the effect of initial substrate pH value on hydrogen production performance and energy conversion efficiencies were discussed.Glucose with concentration of 75 mmol/L was used as carbon source in medium,and the initial substrate pH values were set at 5.5,6.0,7.0,8.0 and 9.0.The light intensity was set at 1 000 lx and operation temperature was 30 ℃.The experimental results showed that the weak alkaline condition was favorable for the growth of photosynthetic bacteria,and after 96 hours' operation for hydrogen production,the total hydrogen production and the maximum hydrogen production rate was 8.0 mmol and 3.39 mmol g-1(cell dry weight) h-1 at the optimal pH 7.0,respectively.The produced hydrogen purity was 70%,and the substrate energy conversion efficiency and light energy conversion efficiency were 1.98% and 7.7%,respectively.It was also found that the substrate energy conversion efficiency,light energy conversion efficiency,hydrogen production and hydrogen production rate were higher in acidic substrate than in alkaline substrate,while the hydrogen purity increased with the increase of initial substrate pH value