If you are saying it was some precipitation around colonies, how could it be ethanol (in precipitated form). As the melting point of ethanol is around -140 degree C whereas if it contains some mixtures/impurities still its melting point be around -120 degree C. I mean to say if it was ethanol, for precipitation it needs very very low temperature.

May be the precipitated product is something also a metabolite or the precipitation of some media component due to production of some metabolite. You can google search the possible reason.

I am also excited to see the experts advice and suggestions here.

Best of Luck.

I agree it can not be ethanol, but may be some salt is getting precipitated out. Look after the composition of the media and you may get some idea regarding the precipitates.

The precipitates may contain ethanol,but not the only one ,maybe some compositions of the media that are not dissolved in ethanol. Take out the precipitates,do some analyse,

Precipitation cannot be ethanol but it may be underutilized components of media

Ethanol is used for the precipitation of cellular polysaccarides and glycoproteins so it could be a precipitation of these components by ethanol both of which are being produced by the organism ,or the polysaccharide/proteins from the media (if you using a complex media)

Ethanol is a liquid having boiling point 78C and can be prepared from glucose in the presence of yeast bacteria and water in acidic pH

Precipitation probably is not result of ethanol presence in agar. You can isolate specific parts of agar and try to extract and analyze the compounds present in agar structure (especially ethanol). However, positive fermentation properties of your yeast strain can be only investigated by growing strain in broth and measuring the ethanol production yield and observation of CO2 production.