Developing a nonmembrane separation system to enable real-time recovery of acetone-butanol during fermentation

Authors: OKONKWO, CHRISTOPHER - The Ohio State University; DUDUYEMI, ADEMOLA - The Ohio State University; UJOR, VICTOR - University Of Wisconsin; Qureshi, Nasib; EZEJI, THADDEUS - The Ohio State University

Submitted to: Applied Microbiology and Biotechnology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/22/2024
Publication Date: 11/9/2024
Citation: Okonkwo, C.C., Duduyemi, A., Ujor, V.C., Qureshi, N., Ezeji, T.C. 2024. Developing a nonmembrane separation system to enable real-time recovery of acetone-butanol during fermentation. Applied Microbiology and Biotechnology. https://doi.org/10.1007/s00253-024-13340-x.
DOI: https://doi.org/10.1007/s00253-024-13340-x

Interpretive Summary: Butanol is a superior fuel compared to ethanol because it packs more energy and has better fuel properties. Another added advantage of butanol production is that it can be produced from lignocellulosic biomass which is less costly than corn or starch containing crops. However, one of the major hinderance or drawback of butanol production is its energy intensive recovery from fermentation broth. To make its recovery energy efficient, new product recovery methods have been sought with limited success. In the present study, we developed an energy efficient method to recover butanol from fermentation broth. In this method, stainless steel wire meshes with various pore sizes were coated with a thin layer of material to improve their properties for separating butanol and water mixtures. The membrane so developed was effectively used to recover butanol from the reaction mixture. It is anticipated that this development would bring butanol production closer to commercialization which would benefit the biofuel industry and the environment.

Technical Abstract: Methods such as gas stripping and vacuum assisted gas stripping (VAGS) processes result in significant removal of water from the bioreactor, thus requiring continuous water replenishment in the bioreactor. In this study, we developed a nonmembrane hydrophobic stainless steel meshes capable of selectively recovering concentrated ABE stream from the bioreactor during VAGS. Three stainless steel meshes with pore sizes of 180, 300 and 425 µm were made hydrophobic and oleophilic with zinc oxide (ZnO) and polydimethylsiloxane (PDMS). Butanol concentrations in the model solutions range from 3 g/L to 10 g/L which mimic concentrations typically produced during batch ABE fermentation. The meshes were integrated in a 5-L bioreactor containing 2.5 L of operational ABE model solution followed by the evaluation of selective extraction of ABE from both cell-free and Clostridium beijerinckii-rich ABE model solutions. The results show that the 180 µm ZnO/PDMS-coated mesh retained 54 – 64% more water in the bioreactor without C. beijerinckii cells and 61 – 65% more water with cells compared to the uncoated mesh. Furthermore, the butanol concentration of condensates recovered with 180 µm ZnO-PDMS-coated mesh was up to 10.8-fold greater than that of uncoated counterpart. Our data demonstrate that the developed ZnO-PDMS mesh can recover high concentrations of ABE while selectively retaining water in the bioreactor. Additionally, this technology demonstrates the potential of the technology for real-time ABE recovery during the fermentation of lignocellulosic and colloidal materials, without the concern of clogging the separation system.