Conversion of individual and mixed volatile fatty acids to hydrogen by Rhodopseudomonas capsulata

A combination of photosynthetic bacteria, which can utilize volatile fatty acids (VFAs) as a carbon source for growth and production of H-2, with anaerobic acidogenic bacteria is an ideal option for efficient H-2 production from wastewater. In the present work, H-2 production by Rhodopseudomonas capsulata from three individual VFAs, i.e. acetate, propionate and butyrate, and a mixture of the three, was investigated. H-2 yields were 0.65 for acetate, 0.28 for propionate and 0.24 for butyrate, respectively, whereas the corresponding maximum H-2 production rates were 17.7, 16.0 and 5.8 ml l(-1) h(-1). A higher acetate and propionate concentration was beneficial for both cell growth and H-2 production. In contrast, a higher butyrate concentration favoured cell growth, but was detrimental to H-2 production. A mixture of 1.9 g l(-1) acetate, 0.4 g l(-1) propionate and 0.8 g l(-1) butyrate was readily utilized by R. capsulata for H-2 production with a yield of 0.34 and maximum H-2 production rate of 14.5 ml l(-1) h(-1). The consumption rate for individual and mixed VFAs by R. capsulata followed the order acetate > propionate > butyrate. (c) 2006 Elsevier Ltd. All rights reserved.