2.3. Inoculation

A homoacetogenic chemolithoautotrophic cultivated mixed inoculum was obtained from a previous MES setup continuously working in our laboratory for CO₂ sequestration mode [12]. The unwanted methanogenic microbial population was inactivated from anaerobic sludge via two-stage enrichment of chemolithoautotrophic microbes. Mixed consortia pretreatment was conducted via the addition of 2 mL (from 500 mM stock solution, to inhibit growth of methanogens) 2-bromoethanesulfonic acid (BESA), supplemented with H₂ and CO₂ in the second stage. Prior to inoculation in MES, pre-treated culture was revived via inoculation of 100 mL of synthetic wastewater with 2 g/L of sodium bicarbonate as a carbon source [5,34].