Just need the answers to a few questions that I cant find anywhere on the internet:
How long does it take for protien to be excreted in the form of urea?
Is how much enzyme you use related to the amount of substrate? Would a 1% solution of enzymes per 20cm3 be enough for a 1% solution of substrate per 100cm3?
I can't give a precise figure for how long protein takes to be excreted (it is not that simple) but it would be within than 24 hours for any amino acids that were in excess. You need to use enough enzyme to make sure that enzyme concentration is not a limiting factor, so it is related to substrate.
I don't really understand your last question - you can't have a solution of 1% enzymes per 20cm3 . If its 1% its 1% irrespective of volume! It is generally OK if the enzyme and the substrate are the same concentrations, but the optimum concentrations are usually a matter of trial and error.