Tunable production of ethanol and acetate from synthesis gas by mesophilic mixed culture fermentation in a hollow fiber membrane biofilm reactor

Researches on environmentally friendly pathways in mixed culture fermentation (MCF) to convert synthesis gas (syngas), including carbon monoxide (CO) and hydrogen (H-2), to biofuels and chemicals are attracting worldwide attention. The hollow-fiber membrane biofilm reactor (HFMBR) offers a potential technology for in-situ utilization of syngas. In this work, the performance of syngas MCF in the HFMBR at acidic pH 4.5 was studied for the first time. Sole ethanol was produced using an HFMBR in batch mode and the maximum concentration reached 16.9 g/L. The results also showed that the partial pressure of H-2 (P-H2) and CO (P-CO) could tune the acetate and ethanol production in HFMBR, in a manner whereby high P-H2 and P-CO favored ethanol production, while low P-H2 and P-CO benefited acetate production. Microbial analysis revealed that the dominant genus in the HFMBR biofilm was Clostridium (86.3%), which is consistent with the experimental results. Overall, the adjustable production of acetate and ethanol from syngas in an HFMBR would be useful for the utilization of syngas MCF in the future. (C) 2018 Elsevier Ltd. All rights reserved.