Doubt filtration would work for emulsions. In any case, the natural lipid/bacterial mixture identified as having potential antimicrobial activity already has a bacterial presence so sterilization by any means would be largely after the fact. You could try other lipid mixtures If the question is just the capability of the microbe, but you really ought to get one of similar composition to the natural if that (assume in situ efficacy) is your primary concern.
Yup - that's what I meant in offering the oleic acid as a source of unsaturated fatty acid - as you say monounsaturated.
i don't see much you can do that's defensible with the bacteria-lipid starting material. From your discussion, can we assume this natural lipid is obtained from skin? There's prob. enough data re. composition of skin lipids that you can assemble a reasonable mixture modeling the system that wouldn't include your isolate. The agar manipulations will be a little awkward but you can figure something out. Be aware that esterase-produced fatty acid can affect pH sufficiently to inhibit. Adding buffered media to test might help disclose if inhibition is seen and you could also include or add after growth Calcium salt to make the fatty acid soap.
btw - did you generate a standard curve that includes these bacterial titers - or were these just 2 isolated observations? You should ensure that you can (by standard curve) differentiate between such high concentrations of cells.
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