You need to pay attention to the bacteria that you use because the bacteria in the colon tend to be different to the ones higher up in the digestive system. Bifido are the ones that like the colon and they are anaerobic.
It might be worth you reading up on different types of bacteria because there are many and you do need to get it right.
There is a little info on the following site. You might notice the book that they are trying to sell. lol Most of the info can be found on the internet.