Effects of culture conditions on cell growth and lipid production in the cultivation of Methylomicrobium buryatense with CH4 as the sole carbon source

Methanotrophs have been explored for decades in applications ranging from bioremediation to specialty chemical production to single cell protein production due to the broad substrate range of the enzyme, methane monooxygenase (MMO) and to the abundance and relatively low cost of methane. This class of bacteria is unique in the ability to utilize methane as both sole carbon and energy source in aerobic growth.  A new concept for methanotrophs is the bioconversion of methane to lipids for diesel fuel production via a hydrodeoxygenation process. This concept reflects a changing value proposition based on the low prices of natural gas, increasing amounts of stranded natural gas due to fracking for liquid petroleum, and increasing demands of liquid transportation fuels.  As a result of this situation, significant attention is being focused on methanotropic bacteria for liquid fuel production. In this study, cultivation experiments with the promising methanotrophic production strain, Methylomicrobium buryatense, were performed to study the cell growth and lipid production in a nitrate minimal salts medium under various culture conditions with CH₄ as the carbon source. A safe, continuous sparging system with gas substrates was developed for this work. The effects of the ratio of O₂ and CH₄, agitation rate, gas flow rates, and nutrient feed strategies on the cell growth and lipid production were investigated. We will present our progress towards goals established for a cost-effective liquid fuel production process.