Characterization of Lipid Accumulation by Rhodococcus rhodochrous Grown on Waste Substrates

EPA Grant Number: F13A31467
Title: Characterization of Lipid Accumulation by Rhodococcus rhodochrous Grown on Waste Substrates
Investigators: Shields-Menard, Sara
Institution: Mississippi State University
EPA Project Officer: Packard, Benjamin H
Project Period: August 18, 2014 through August 18, 2016
Project Amount: $84,000
RFA: STAR Graduate Fellowships (2013) RFA Text |  Recipients Lists
Research Category: Academic Fellowships , Fellowship - Microbiology


Current biodiesel feedstocks, such as crop oils, account for 60–75 percent of total biodiesel production costs; however, undesired waste streams are plentiful and often contain sources of carbon that can be degraded by bacteria. Oleaginous microbes are those that accumulate more than 20 percent of their biomass as intracellular lipids, which can be converted into biodiesel. This research will investigate the ability of the bacterium R. rhodochrous, known for bioremediation of contaminants, to use waste sources as a feedstock for lipid accumulation.


The growth and lipid accumulation of R. rhodochrous will be investigated when cultivated in a minimal salts medium supplemented with model lignocellulosic sugars and inhibitors, including glucose, xylose, acetic acid, furfural and phenolic lignin compounds. Cell dry weight measurements will determine growth and survival in these substrates, and gas chromatography and sugar analysis will show if the substrate has been consumed by R. rhodochrous. Lipid accumulation will be observed using transmission electron microscopy and quantified by lipid extraction. Genomic sequencing and proteomic analysis of R. rhodochrous will give us further insight at a molecular level into growth and lipid accumulation.

Expected Results:

The potential to couple the utilization of diverse substrates with lipid accumulation in R. rhodochrous offers a promising approach to alternative fuels. Due to the diverse metabolism of R. rhodochrous, growth and survival in the various substrates is expected. Lipid accumulation will be observed in transmission electron microscopy images and is likely to occur in cultures containing glucose. The inhibitors could potentially reduce lipid yields; however, conversion of those inhibitors into less toxic compounds could prove useful for other commercial applications.

Potential to Further Environmental/Human Health Protection

The unstable price of oil, growing environmental concern of fossil fuel overuse and increasing government awareness have brought alternative energy solutions to the forefront of multidisciplined scientific research. Oleaginous microbes offer a unique advantage in producing lipid for biodiesel feedstock because of their ability to grow on diverse substrates in a controlled environment, resulting in a sustainable source of biodiesel feedstock. Characterization of lipid accumulation by R. rhodochrous grown on waste sources is a critical step in repurposing potential environmental contaminants into a sustainable fuel alternative.

Supplemental Keywords:

biofuel, bioremediation, oleaginous microbes

Progress and Final Reports:

  • 2015
  • Final