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

Abstract

Abstract:In this study, the photo fermentative H 2 production of Rhodobacter sphaeroides KCTC 1434 was investigated using acetate, propionate and butyrate under argon and nitrogen headspace gases. The highest H 2 yield and Substrate Conversion Efficiency (SCE) were observed from butyrate (8.84 mol H 2 /mol butyrate consumed, 88.42% SCE) and propionate (6.10 mol H 2 /mol propionate consumed, 87.16% SCE) under Ar headspace. Utilization of acetate was associated with low H 2 evolution, high biomass yield and high final pH, which suggest that acetate uptake by the strain involves a biosynthetic pathway that competes with H 2 production. The use of N 2 in sparging resulted to a decreased H 2 productivity in propionate (0.49 mol H 2 /mol propionate consumed, 7.01% SCE) and butyrate (1.22 mol H 2 /mol butyrate consumed, 1.04% SCE) and was accompanied with high biomass yield and radical pH increase in all acids. High H 2 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 H 2 generation. This suggests that a more refined culture condition such as additional control of pH during fermentation must be kept to enhance the H 2 productivity. Overall, the study provided a background on the H 2 production using R. sphaeroides KCTC 1434 which might be a good co-culture candidate because of its high SCE on butyrate and propionate.

Optimization of H2 Production through Minimization of CO2 Emissions by Mixed Cultures of Purple Phototrophic Bacteria in Aqueous Samples

“…However, in the absence of N 2 , nitrogenase exclusively reduces protons towards maximal H 2 production [14]. These findings are in accordance with other studies, reporting that the amount of H 2 produced from propionate and butyrate, decreased under N 2 gas phase growth of R. sphaeroides [19].…”

“…Nevertheless, glutamate is considered an excellent substrate for hydrogen production, since it serves simultaneously as carbon and nitrogen source [18]. Finally, dinitrogen, which serves as the natural substrate of nitrogenase, inhibits the hydrogen production rate, since N 2 fixation and biohydrogen production are two competing processes [19].…”