Free fatty acids are merely carboxylic acids with long hydrocarbon chains. They are produced when fats are broken and considered as good fats. Free fatty acids can be used as precursors of fatty acid methyl esters (FAMEs) which are used as diesel. Currently, alternative fuels of which feedstock is originated in the nature or which was made by biological methods have been greatly interested as they do not increase the net carbon dioxide, one of the greenhouse gases that enhance radioactive force and contribute to global warming.
Rhodococcus opacus PD630 is able to accumulate lipids up to 76 or 87% of the cellular dry mass as triacylglycerides (TAG), diacylglycerides (DAG) and wax esters etc. respectively. To produce free fatty acids using these lipids, the genes encoding TAG lipase, monoacylglyceride (MAG) lipase from other organisms were overexpressed in R. opacus PD630 using the R. opacus PD630-Escherichia coli shuttle vectors. For accumulating lipids in R. opacus PD630, mineral salt media (MSM) cultivation was optimized and MSM cultivation without nitrogen source was used. Produced free fatty acids from these cultures were chemically converted into FAMEs by methylation.
As a result, the mutant R. opacus PD630 strain was able to produce free fatty acids with 50% of free ratty acids yield from glucose in contrast with R. opacus PD630 wild strain having ability to produce with 33.5% of free fatty acids yield from glucose. From these fatty acids, FAME ?? diesel was produced by chemical method and the concentration was 5.393g/l using free fatty acids which were produced from fed-batch fermentation.