Its kind of a tough area with DIY CO2 as far as inhibiting bacterial growth...generally when making beer and wine, you pitch a large amount right off the bat to give the yeast a strong start. That way, the yeast really takes off and prevents bacterial infections from establishing. However, by doing that, about 90% of the ferment is over within 48-72 hours. Not good when you're trying to make that batch last. The best way would be to sanitize everything that comes in contact with the solution really well to try and prevent bacteria intrusion in the first place.
