Isolation, Development, and Genomic Analysis ofBacillus megateriumSR7 for Growth and Metabolite Production Under Supercritical Carbon Dioxide

Abstract

AbstractSupercritical 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 scCO2are mainly limited toin vitroprocesses 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 scCO2reservoir in aqueous media under scCO2headspace enabled the isolation of spore-forming strainBacillus megateriumSR7. 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 withL-alanine for chemical induction of spore germination significantly improved growth frequencies and biomass accumulation under scCO2headspace. Detection of endogenous fermentative compounds in cultures grown under scCO2represents the first observation of bioproduct generation and accumulation under this condition. Culturing development and metabolic characterization ofB. megateriumSR7 represent initial advancements in the effort towards enabling exploitation of scCO2as a sustainable solvent forin vivobioprocessing.