Carbon Monoxide Sensitivity to Hydrogen Consumption in Eubacterium limosum KIST612

Abstract

Syngas, a mixture of mostly hydrogen (H2), carbon monoxide (CO), and carbon dioxide (CO2), is used as a carbon and energy source by certain anaerobic microorganisms, called acetogens. Acetogens are strictly anaerobic bacteria which are able to utilize syngas components (H2, CO, and CO2) through the Wood-Ljungdahl pathway (WLP). In this study, we have tested substrate utilization and selectivity of Eubacterium limosum KIST612 when the strain was cultivated in the medium containing H2, CO2, and CO, respectively. The result showed that H2 consumption was completely inhibited when the dissolved CO concentration is over 0.05 ± 0.01. To reveal the reason, the biochemical properties of [FeFe]-hydrogenase would be investigated. We conducted hydrogenase activity and CO inhibition test on whole crude extract of Eubacterium limosum KIST612 that cultivated different type of substrate such as 20mM glucose, 1 atm of CO, and 1 atm of H2CO2. Also the subunits of Hyd were successfully expressed in Escherichia coli DH5α This study suggests the guideline for enhanced productivity by optimizing to consume co-substrate in syngas fermentation.