I am going to screen a large repository of bacteria and fungi for their ability to produce polyunsaturated fatty acids (PUFAs). We have an assay from Ryan 2010 to use TTC to indicate the putative PUFA producers, but it looks like they had ~50% false positive rates. We are planning to do a larger study on the positive producers, but we would like to know if the organisms are actually producing any Omega-3's before we take the deeper dive.

Are there any (cheap/relatively quick) assays that can qualitatively say if a sample is actually producing any Omega-3?

Much of the literature used some GC-MS (or similar technique) to determine the fatty acid content (we will eventually go down this road) and all the commercial products I have seen look like they can broadly detect free-fatty acids. Unfortunately, while this could be a start, we are particularly interested in the Omega-3 and wish not to use the more labor intensive methods for a secondary screen.