Lipid Accumulation by Rhodococcus Rhodochrous

Oleaginous microbes can accumulate over 20% of their cell dry weight as lipids that are stored as intracellular energy reserves. The characterization of other oleaginous bacteria creates opportunities for the development of alternative feedstocks and technologies. Rhodococcus rhodochrous is a gram-positive bacterium known for its biodegradation capabilities, but little is known about its ability to accumulate lipids. As R. rhodochrous is capable of degrading hydrocarbon gasses and other aromatics, this study aims to investigate any associated lipid production during the conversion of waste and nontraditional carbon sources, such as model lignocellulosic inhibitors. Lignocellulosic biomass is the most abundant and renewable organic material in the world and is composed of cellulose, hemicellulose, and lignin, which can be pretreated to release sugars from the complex, and often recalcitrant, lignin polymer for microbial fermentation. R. rhodochrous was cultivated with various carbon sources, including glucose, xylose, acetic acid, furfural, phenol, vanillic acid, hydroxybenzoic acid, and propane. The results suggest that R. rhodochrous can survive in the presence of these compounds, achieving almost 7g/L cell dry weight after 168 hours and still accumulate up to 40-50% of cell dry weight as lipid in glucose supplemented media. Furthermore, the aromatic compounds are undetected after 48 hours indicating that R. rhodochrous was able to tolerate these compounds and accumulate lipids. Fatty acid methyl ester profiles show a prevalence of palmitic and oleic methyl esters. Overall, these studies are contributing to a better understanding and characterization of another oleaginous Rhodococcus species, Rhodococcus rhodochrous