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Energy security, environmental concerns, and unstable oil prices have been the driving trifecta of demand for alternative fuels in the United States. The United States’ dependence on energy resources, often from unstable oil-producing countries has created political insecurities and concerns. As we try to gain energy security, unconventional oil becomes more common, flooding the market, and causing the major downshift of the usual unstable oil prices. Meanwhile, consumption of fossil fuels and the consequent CO 2 emissions have driven disruptions in the Earth’s atmosphere and are recognized to be responsible for global climate change. While the significance of each of these three factors may fluctuate with global politics or new technologies, transportation energy will remain the prominent focus of multi-disciplined research. Bioenergy future depends on the price of oil. Current energy policy of the United States heavily favors petroleum industry. In this review, the current trend in microbial lipids as a potential biofuel is discussed. [ABSTRACT FROM AUTHOR]

Lignocellulosic biomass is one of the most abundant and renewable organic materials in the world. The lignocellulosic complex is composed of cellulose, hemicellulose, and lignin, which can be pretreated to release sugars that can be utilized for microbial production of valued metabolites. Oleaginous microbes can accumulate over 20% of their cell dry weight as lipids, which are stored as intracellular energy reserves. The characterization of oleaginous bacteria creates opportunities for the development of alternative feedstocks and technologies. Rhodococcus rhodochrous is a bacterium recently determined to be oleaginous when grown in glucose-supplemented media. The purpose of this study was to evaluate model lignin phenolic compounds as substrates for lipid accumulation. Lipid accumulation in R. rhodochrous was evaluated using phenol, 4-hydroxybenzoic acid (HBA) and vanillic acid (VA) as model lignin compounds with and without glucose as a co-substrate. Cell dry weight increased in all treatments, indicating that growth was not impaired in these conditions. However, alterations were observed in the amount of lipids produced. Dry cell weight and lipids were analyzed daily. R. rhodochrous accumulated over 40% of its cell dry weight as lipids when grown in glucose with HBA and VA, but less than 20% when grown in HBA and VA alone. When grown in phenol and glucose, R. rhodochrous accumulated 35% of its dry weight at lipids, but did not accumulate lipids when grown in phenol alone. These data indicate that R. rhodochrous may have the capability to tolerate and utilize lignin-like aromatic compounds for lipid accumulation. [ABSTRACT FROM AUTHOR]