Lipid Accumulation by Rhodococcus rhodochrous Grown on Model Lignocellulosic Sugars

As interest in renewable fuels increases, oleaginous microbes are at the forefront of multi-disciplined research. The characterization of other oleaginous bacteria creates opportunities for the development of alternative feedstocks and technologies. Rhodococcus rhodochrous is a red-pigmented, gram-positive, soil bacterium commonly used for industrial production of acrylamide and for bioremediation of hydrocarbons and aromatic compounds. Despite the widespread use of R. rhodochrous in industry, the understanding of its ability for lipid accumulation is limited. This research aims to determine the lipid accumulation capabilities of Rhodococcus rhodochrous in an effort to offer a unique approach to addressing the need for alternative fuels.  Shake flask experiments were performed using glucose or xylose as a substrate with limited nitrogen conditions to promote lipid accumulation. Glucose experiments were supplemented with acetic acid and furfural to investigate any inhibitory effects of these compounds. Cells from all treatments were harvested daily and lipids were extracted from total cell dry weight using a modified Bligh and Dyer method. R. rhodochrous accumulated 52% of cell dry weight as lipid after 5 days of growth in 20g/L of glucose. Minimal growth was observed when R. rhodochrous was grown in xylose. In the presence of 3g/L of acetic acid (sodium acetate) and glucose, 50% lipid accumulation by cell dry weight was observed in R. rhodochrous. Similar results were observed with the addition of 0.3ml/L furfural suggesting that R. rhodochrous is not inhibited by the addition of furfural or acetic acid in the media.