H2 enrichment from synthesis gas by Desulfotomaculumcarboxydivorans for potential applications in synthesis gas purification and biodesulfurization

Abstract

Desulfotomaculum carboxydivorans, recently isolated from a full-scale anaerobic wastewater treatment facility, is a sulfate reducer capable of hydrogenogenic growth on carbon monoxide (CO). In the presence of sulfate, the hydrogen formed is used for sulfate reduction. The organism grows rapidly at 200 kPa CO, pH 7.0, and 55°C, with a generation time of 100 min, producing nearly equimolar amounts of H 2 and CO 2 from CO and H 2 O. The high specific CO conversion rates, exceeding 0.8 mol CO (g protein) −1 h −1 , makes this bacterium an interesting candidate for a biological alternative of the currently employed chemical catalytic water-gas shift reaction to purify synthesis gas (contains mainly H 2 , CO, and CO 2 ). Furthermore, as D. carboxydivorans is capable of hydrogenotrophic sulfate reduction at partial CO pressures exceeding 100 kPa, it is also a good candidate for biodesulfurization processes using synthesis gas as electron donor at elevated temperatures, e.g., in biological flue gas desulfurization. Although high maximal specific sulfate reduction rates (32 mmol (g protein) −1 h −1 ) can be obtained, its sulfide tolerance is rather low and pH dependent, i.e., maximally 9 and 5 mM sulfide at pH 7.2 and pH 6.5, respectively.

A Post-Genomic View of the Ecophysiology, Catabolism and Biotechnological Relevance of Sulphate-Reducing Prokaryotes

“…From the perspective of energy efficiency, conversion of CO with H 2 O to CO 2 and H 2 is a desired process, which can be accomplished by anaerobic bacteria, including SRB (Sipma et al, 2006). Hydrogen-evolving growth with CO has been exemplified with D. carboxydivorans (Sipma et al, 2007). SRB have furthermore been implicated in biological desulphurization (SO 2 removal) of flue gas, by recycling gypsum produced during adsorption and chemical oxidation of SO 2 (Kaufman, Little, & Selvaraj, 1997) or by reducing sulphate from alkaline adsorption fluid (Zhou, Song, et al, 2014).…”

Diversity and ecophysiological features of thermophilic carboxydotrophic anaerobes

“…Trace levels of CO were observed in methanogenic bioreactors (Hickey et al , 1987; Bae & McCarty, 1993). Some bioreactors are fed with synthesis gas, consisting of H 2 , CO, and CO 2 , as a cheap source of hydrogen used in various biological reductive reactions, but a content of 5–60% CO in the synthesis gas limits its direct industrial application (Sipma et al , 2006, 2007). CO in hydrothermal environments originates from volcanic gases (Menyailov & Nikitina, 1980; Symonds et al , 1994; Allard & Barton, 2004).…”

Carbon Monoxide as an Electron Donor for the Biological Reduction of Sulphate

“…carboxydivorans were not inhibited by the highest tested P CO of 200 and 124 kPa, respectively [14, 56]. Presence of a CO-dehydrogenase in a sulphate reducer does not necessarily mean that it is less sensitive towards CO.…”

“…However, Dtm. carboxydivorans has a pH-dependent sensitivity for sulphide inhibition, that is, 9 mM sulfide at pH 7.2 and 5 mM at pH 6.5 cause complete inhibition [56]. Thus, most likely not toxicity of CO, but of sulphide determines the sulphate reduction capacity of Dtm.…”