H2consumption by acetogenic bacteria follows first-order kinetics

Abstract

AbstractAcetogenic bacteria play an important role in various environmental and biotechnological processes, because of their autotrophic metabolism converting carbon dioxide with molecular hydrogen (H2) as electron donor into acetate. The main factor limiting acetogenesis is often H2. Assessing the potential of acetogens in environmental and biotechnological processes thus requires insights into their H2consumption kinetics. In this study, initial H2consumption rates at a range of different initial H2concentrations were measured for three different acetogens. Interesting, for all three strains, H2consumption was found to follow first-order kinetics, i.e. the H2consumption rate increased linearly with the dissolved H2concentration up to almost saturated H2levels. This contradicts Monod kinetics, which is commonly assumed for acetogens. The obtained first-order rate coefficients (k1) were further validated by fitting first-order kinetics on previous time-course experimental results. The latter method was also used to determine thek1value of five additional acetogens strains. Biomass specific first-order rate coefficients were found to vary up to six-fold, with the highestk1forAcetobacterium wieringaeand the lowest forSporomusa sphaeroides. Overall, our results demonstrate the importance of the dissolved H2concentration to understand the rate of acetogenesis in environmental and biotechnological settings.SynopsisAcetogenic bacteria are diverse, although they catalyze the same overall reaction. This study provides insights into their different H2consumption rates, which has implications for their role in the environment and in biotechnological applications.