EPSCoR Research Fellows: NSF: Unravelling Mechanisms of Simultaneous Growth and Lipid Accumulation in Rhodococcus opacus Using a Systems Biology Approach

This project would provide a fellowship to an Associate Professor and training for a graduate student at the University of Wyoming. This work will be conducted in collaboration with researchers at the National Renewable Energy Laboratory. A long-standing challenge to the economical production of lipid-based biofuels, such as biodiesel, relates to how and when cells accumulate lipids.

Lipid accumulation is triggered upon cell stress severe enough that it also arrests cell growth; therefore, cells must first be grown and then transferred to different conditions to trigger significant lipid accumulation. We have developed a simple system in which the bacterium Rhodococcus opacus PD630 grows on a dilute agricultural by-product with significant lipid accumulation during growth.

This system is unique because it outperforms attempts to engineer microbial lipid accumulation during growth. The goals of this work are to: 1) identify which feature(s) of the agricultural by-product stimulates lipid accumulation during growth for identification of other cheap, abundant feedstocks and 2) understand how cells accumulate lipids during growth so this can be engineered into other microbial systems for economical bioproduction.

To accomplish this, the deep expertise in lipid-accumulating microbes at the National Renewable Energy Laboratory will be leveraged to understand how our unique system works. The results of this project will be used to identify strategies to engineer other microbial systems for a simpler, more economical production of renewable, lipid-based biofuels and biochemicals.

This project directly addresses a long-standing challenge for economical microbial biofuel production.

The overall goal of the project is to identify targets for the forward engineering of other systems to stimulate lipid accumulation during growth for economical microbial lipid production. This research directly addresses a long-standing challenge to economic microbial lipid production with the overall goal of moving to a renewable bioeconomy for fuels and materials.

The PI developed a system in which the bacterium Rhodococcus opacus PD630 grows on a dilute agricultural by-product with significant lipid accumulation during growth, with biomass accumulation to ~3 g/L (dry weight) in 48 hours of batch culture. The collected biomass is 43% fatty acids, which is equal to that observed when R. opacus PD630 is grown on glucose and growth-arrested for ideal lipid accumulation conditions in the laboratory.

This NSF EPSCoR RII EPSCoR Research Fellows project will support the PI and a graduate student to work with an expert in lipid-accumulating microbes at the National Renewable Energy Laboratory. Working together, the PI and collaborator will determine: 1) which characteristics of the dilute agricultural by-product are critical for lipid accumulation during growth and 2) which metabolic pathways are active when cells accumulate lipids during growth.

The dilute agricultural by-product will be characterized by the measurement of total organic carbon, inorganic carbon, total nitrogen, major and minor ions, as well as organic acids and sugars in the by-product before, during, and after growth. Individual components will be added to the medium to assess impacts on lipid accumulation. Metabolic pathways active during simultaneous growth and lipid accumulation will be identified through transcriptomic, lipidomic, and untargeted metabolomic analysis.

This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.