Microbial Electrosynthesis of Acetate Powered by Intermittent Electricity

Abstract

Microbial electrosynthesis (MES) of acetate is a process using electrical energy to reduce CO2 to acetic acid in an integrated bioelectrochemical system. MES powered by excess renewable electricity produces carbon-neutral acetate while benefitting from inexpensive but intermittent energy sources. Interruptions in electricity supply also cause energy limitation and starvation of the microbial cells performing MES. Here, we studied the effect of intermittent electricity supply on the performance of hydrogen-mediated MES of acetate. Thermoanaerobacter kivui produced acetic acid for more than 4 months from intermittent electricity supplied in 12 h on–off cycles in a semicontinuously-fed MES system. After current interruptions, hydrogen utilization and acetate synthesis rates were severely diminished. They did not recover to the steady-state rates of continuous MES within the 12 h current-on period under most conditions. Accumulating high product (acetate) concentration exacerbated this effect and prolonged recovery. However, supply of a low background current of 1–5% of the maximum current during “off-times” reduced the impact of current interruptions on subsequent MES performance. This study presents sustained MES at a rate of up to 2 mM h–1 acetate at an average concentration of 60–90 mM by a pure thermophilic microbial culture powered by intermittent electricity. We identified product inhibition of accumulating acetic acid as a key challenge to improving the efficiency of intermittently powered MES.

Electrochemistry‐Based CO2 Removal Technologies

“…[51] Microbial electrosynthesis, when coupled to metabolicallydependent microorganisms using renewable electricity is a highly favorable platform for production of multi-carbon compounds from CO 2 . [52] This includes e-fuels and chemical precursors such as of methane, acetate, ethanol, caproate, butyrate, and butanol, to name a few compounds. [53] The bioelectrochemical platform is a promising technology for future production of high-value chemicals from biogenic CO 2 .…”

Tandem Acidic CO2 Electrolysis Coupled with Syngas Fermentation: A Two-Stage Process for Producing Medium-Chain Fatty Acids

“…In MES research, generally, cathodic biofilms with direct microbial attachment to the cathode were predominantly utilized. These biofilms harnessed electrical power through either direct electron transfer or mediated electron transfer using H 2 as an energy carrier. − In the past decade, numerous projects focusing on MES at a high technology readiness level (TRL) have been established . However, owing to the limited characteristic density of bacteria and its electron consumption rate, conventional biofilm-based MES has yielded current densities 1–2 orders of magnitude lower than those achieved in industrial electrochemical production. , Consequently, a hybrid process involving tandem CO 2 electrolysis with fermentation was proposed, incorporating electrocatalysts to enhance CO 2 reduction rates .…”

Unassisted stimulation of autotrophic ethanol bioproduction by visible light

“…[11][12][13][14] Over the years, advanced systems have been described where acetogens gain the energy necessary for biological CO 2 reduction from different sources including reduced gases, organic carbons, and electrical current. [15][16][17][18] Recently, hybrid photosynthesis, coupling non-photosynthetic microbes with abiotic photosystems, was developed with the objective of reaching sunlight conversion efficiency and product specicity beyond the state-ofthe-art. [19][20][21][22] In many of these systems, photoelectrochemical cells or particulate photocatalytic semiconductors are powering the autotrophic metabolism of acetogens with photoelectrons.…”