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Front. Microbiol. | doi: 10.3389/fmicb.2018.02152

Isolation, Development, and Genomic Analysis of Bacillus megaterium SR7 for Growth and Metabolite Production Under Supercritical Carbon Dioxide

 Adam J. Freedman1, 2, Kyle C. Peet1, 2,  Jason T. Boock2, Kevin Penn1, 2,  Kristala L. Prather2 and  Janelle R. Thompson1, 2*
  • 1Civil and Environmental Engineering, Massachusetts Institute of Technology, United States
  • 2Chemical Engineering, Massachusetts Institute of Technology, United States

Supercritical carbon dioxide (scCO2) is an attractive substitute for conventional organic solvents due to its unique transport and thermodynamic properties, its renewability and labile nature, and its high solubility for compounds such as alcohols, ketones and aldehydes. However, biological systems that use scCO2 are mainly limited to in vitro processes due to its strong inhibition of cell viability and growth. To solve this problem, we used a bioprospecting approach to isolate a microbial strain with the natural ability to grow while exposed to scCO2. Enrichment culture and serial passaging of deep subsurface fluids from the McElmo Dome scCO2 reservoir in aqueous media under scCO2 headspace enabled the isolation of spore-forming strain Bacillus megaterium SR7. Sequencing and analysis of the complete 5.51 Mbp genome and physiological characterization revealed the capacity for facultative anaerobic metabolism, including fermentative growth on a diverse range of organic substrates. Supplementation of growth medium with L-alanine for chemical induction of spore germination significantly improved growth frequencies and biomass accumulation under scCO2 headspace. Detection of endogenous fermentative compounds in cultures grown under scCO2 represents the first observation of bioproduct generation and accumulation under this condition. Culturing development and metabolic characterization of B. megaterium SR7 represent initial advancements in the effort towards enabling exploitation of scCO2 as a sustainable solvent for in vivo bioprocessing.

Keywords: Supercritical carbon dioxide, Bioprospecting, Strain isolation, Bacillus megaterium, bioprocessing, bacterial spore germination, Bacterial Genomics

Received: 19 Jan 2018; Accepted: 22 Aug 2018.

Edited by:

Ivan Mijakovic, Chalmers University of Technology, Sweden

Reviewed by:

JUN LIU, Tianjin Institute of Industrial Biotechnology (CAS), China
Aida Kalantari, Duke University, United States  

Copyright: © 2018 Freedman, Peet, Boock, Penn, Prather and Thompson. This is an open-access article distributed under the terms of the Creative Commons Attribution License (CC BY). The use, distribution or reproduction in other forums is permitted, provided the original author(s) and the copyright owner(s) are credited and that the original publication in this journal is cited, in accordance with accepted academic practice. No use, distribution or reproduction is permitted which does not comply with these terms.

* Correspondence: Prof. Janelle R. Thompson, Massachusetts Institute of Technology, Civil and Environmental Engineering, 15 Vassar Street, Cambridge, 02139, Massachusetts, United States, jthompson@mit.edu