EMS-Induced Mutagenesis of Clostridium carboxidivorans for Increased Atmospheric CO2 Reduction Efficiency and Solvent Production

Naoufal Lakhssassi; Azam Baharlouei; Jonas Meksem; Scott D Hamilton-Brehm; David A Lightfoot; Khalid Meksem; Yanna Liang

doi:10.3390/microorganisms8081239

EMS-Induced Mutagenesis of Clostridium carboxidivorans for Increased Atmospheric CO₂ Reduction Efficiency and Solvent Production

Microorganisms. 2020 Aug 14;8(8):1239. doi: 10.3390/microorganisms8081239.

Authors

Naoufal Lakhssassi^{1

2}, Azam Baharlouei¹, Jonas Meksem³, Scott D Hamilton-Brehm⁴, David A Lightfoot², Khalid Meksem², Yanna Liang^{1

5}

Affiliations

¹ Department of Civil and Environmental Engineering, 1230 Lincoln Drive, Southern Illinois University Carbondale, Carbondale, IL 62901, USA.
² Department of Plant, Soil, and Agricultural Systems, Southern Illinois University, Carbondale, IL 62901, USA.
³ Trinity College of Arts and Sciences, Duke University, Durham, NC 27708, USA.
⁴ Department of Microbiology, Southern Illinois University, Carbondale, IL 62901, USA.
⁵ Department of Environmental and Sustainable Engineering, 1400 Washington Ave, State University of New York at Albany, Albany, NY 12222, USA.

Abstract

Clostridium carboxidivorans (P7) is one of the most important solvent-producing bacteria capable of fermenting syngas (CO, CO₂, and H₂) to produce chemical commodities when grown as an autotroph. This study aimed to develop ethyl methanesulfonate (EMS)-induced P7 mutants that were capable of growing in the presence of CO₂ as a unique source of carbon with increased solvent formation and atmospheric CO₂ reduction to limit global warming. Phenotypic analysis including growth and end product characterization of the P7 wild type (WT) demonstrated that this strain grew better at 25 °C than 37 °C when CO₂ served as the only source of carbon. In the current study, 55 mutagenized P7-EMS mutants were developed by using 100 mM and 120 mM EMS. Interestingly, using a forward genetic approach, three out of the 55 P7-EMS mutants showed a significant increase in ethanol, butyrate, and butanol production. The three P7-EMS mutants presented on average a 4.68-fold increase in concentrations of ethanol when compared to the P7-WT. Butyric acid production from 3 P7-EMS mutants contained an average of a 3.85 fold increase over the levels observed in the P7-WT cultures under the same conditions (CO₂ only). In addition, one P7-EMS mutant presented butanol production (0.23 ± 0.02 g/L), which was absent from the P7-WT under CO₂ conditions. Most of the P7-EMS mutants showed stability of the obtained end product traits after three transfers. Most importantly, the amount of reduced atmospheric CO₂ increased up to 8.72 times (0.21 g/Abs) for ethanol production and up to 8.73 times higher (0.16 g/Abs) for butyrate than the levels contained in the P7-WT. Additionally, to produce butanol, the P7-EMS_III-J mutant presented 0.082 g/Abs of CO₂ reduction. This study demonstrated the feasibility and effectiveness of employing EMS mutagenesis in generating solvent-producing anaerobic bacteria mutants with improved and novel product formation and increased atmospheric CO₂ reduction efficiency.

Keywords: CO2 reduction efficiency; Clostridium carboxidivorans; EMS mutagenesis; anaerobic bacteria; global warming; increased alcohol production.

Abstract

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