Last meeting (9/11/12) we discussed making fluorescent, glowing beer by making yeast that produce one of the common fluorescent tags. I've poked around on the internet some and there a few considerations about the possibility of making this:
1) GFP (green fluorescent protein) is considered non-toxic, and I have expressed (had cells produce) it in human cells without the cells dying off. A quick literature search can double check this. GFP is not all that stable at the lower end of beer pHs (too acidic), but I need to check on eGFP (enhanced GFP, which is what I've used in the past) and other fluorescent proteins (Red FP and Cyan FP) to see their stability at low pH. This might require tweaking the pH of the beer to make it look pretty.
2) The complexity of what we want to do is based completely on what equipment we can get our hands on. For example, if we can get a thermocycler/PCR machine and invest in some restriction enzymes we could cut and paste DNA together to make the plasmid (circular DNA that would carry the GFP gene) exactly how we want it. Otherwise we might need to use a commercially available plasmid, or one that a local lab could give us a small sample of.
3) To keep the temperature lower it might be a good idea to start with a lager, but I think there are some other options (like adding the modified yeast during a second fermentation or when bottle conditioning.
If people are interested I can get together a list of ingredients and equipment we would need to do this (in addition to the brewing equipment, which we already appear to have).