Continuous H2/CO2 fermentation for acetic acid production under transient and continuous sulfide inhibition

• Published in: Chemosphere (Oxford) Vol. 285; p. 131536
• Main Authors: Ntagia, Eleftheria, Chatzigiannidou, Ioanna, Carvajal-Arroyo, Jose M., Arends, Jan B.A., Rabaey, Korneel
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 01-12-2021; Elsevier
• Subjects: Acetogenesis; CO2 utilization; Environmental Sciences; Gas fermentation; Sulfide stress; Acetogenesis; CO2 utilization; Gas fermentation; Sulfide stress
• ISSN: 0045-6535; 1879-1298
• DOI: 10.1016/j.chemosphere.2021.131536

Waste gas fermentation powered by renewable H2 is reaching kiloton scale. The presence of sulfide, inherent to many waste gases, can cause inhibition, requiring additional gas treatment. In this work, acetogenesis and methanogenesis inhibition by sulfide were studied in a 10-L mixed-culture fermenter, supplied with CO2 and connected with a water electrolysis unit for electricity-powered H2 supply. Three cycles of inhibition (1.3 mM total dissolved sulfide (TDS)) and recovery were applied, then the fermenter was operated at 0.5 mM TDS for 35 days. During operation at 0.5 mM TDS the acetate production rate reached 7.1 ± 1.5 mmol C L−1 d−1. Furthermore, 43.7 ± 15.6% of the electrons, provided as H2, were distributed to acetate and 7.7 ± 4.1% to butyrate, the second most abundant fermentation product. Selectivity of sulfide as inhibitor was demonstrated by a 7 days lag-phase of methanogenesis recovery, compared to 48 h for acetogenesis and by the less than 1% electrons distribution to CH4, under 0.5 mM TDS. The microbial community was dominated by Eubacterium, Proteiniphilum and an unclassified member of the Eggerthellaceae family. The taxonomic diversity of the community decreased and conversely the phenotypic diversity increased, during operation. This work illustrated the scale-up potential of waste gas fermentations, by elucidating the effect of sulfide as a common gas impurity, and by demonstrating continuous, potentially renewable supply of electrons.
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•A 10-L scale CO2 fermentation was tested using reducing power obtained by electrolysis.•Sulfide at 1.3 mM inhibits acetogenesis but the effect is reversible.•1.3 mM TDS irreversibly suppressed methanogenesis in H2/CO2 fermentation.•Under sulfide stress acetogenesis shifts towards higher butyrate production.