It's the strangest list of components I've ever seen, but a lemon is the final thing we need.
Yes, a lemon. No, I'm not joking.
You won't find it in the lunch room, either. ?
Check the various labs again.
Nowhere - you'll find lemon seeds in a very unlikely place, though - the bio lab.
Apparently the hellspawn in the cage poops out lemon seeds.
If we fed the little fella, it might reward us... with poop.
Try finding something to feed it with.
Something edible, but not something you'd eat yourself.
Take the 'cheese puffs' from the lunch room, then put them in the cage's feeder. If Vinny decides to eat them himself, you'll need these hints.
Repeat the feeding process until you have the lemon seeds.
Don't celebrate quite yet - we need to do some science before these seeds become a full-on lemon.