The present invention provides a process for the production of a microbial oilcomprising culturing a micro-organism in a two stage fermentation processwhere, in a last stage that precedes the end of fermentation, the carbonsource is: consumed by the micro-organisms at a rate greater than it is addedto the medium； added at a rate <；= 0.30 M carbon/kg medium； or is rate limitingon the growth of the micro-organism. The micro-organisms thus have the carbonsource restricted so that they preferentially metabolise fats or lipids otherthan arachidonic acid (ARA), so increasing the proportion of ARA in the cells.A microbial oil is then recovered from the micro-organism, using hexane as asolvent, that has at least 50% ARA and at least 90% triglycerides.
