Investigation of the Photoheterotrophic Hydrogen Production of <i>Rhodobacter sphaeroides</i> KCTC 1434 using Volatile Fatty Acids under Argon and Nitrogen Headspace

Abstract

In this study, the photo fermentative H2 production of Rhodobacter sphaeroides KCTC 1434 was investigated using acetate, propionate and butyrate under argon and nitrogen headspace gases. The highest H2 yield and Substrate Conversion Efficiency (SCE) were observed from butyrate (8.84 mol H2/mol butyrate consumed, 88.42% SCE) and propionate (6.10 mol H2/mol propionate consumed, 87.16% SCE) under Ar headspace. Utilization of acetate was associated with low H2 evolution, high biomass yield and high final pH, which suggest that acetate uptake by the strain involves a biosynthetic pathway that competes with H2 production. The use of N2 in sparging resulted to a decreased H2 productivity in propionate (0.49 mol H2/mol propionate consumed, 7.01% SCE) and butyrate (1.22 mol H2/mol butyrate consumed, 1.04% SCE) and was accompanied with high biomass yield and radical pH increase in all acids. High H2 generation had shown to improve acid consumption rate. The use of the three acids in a mixed substrate resulted to a drastic pH rise and lower H2 generation. This suggests that a more refined culture condition such as additional control of pH during fermentation must be kept to enhance the H2 productivity. Overall, the study provided a background on the H2 production using R. sphaeroides KCTC 1434 which might be a good co-culture candidate because of its high SCE on butyrate and propionate.