Brewers yeast is inactive yeast, so it doesn't actually inhibit mold, but it provides nutrients and protein. I've heard of alot of people sprinkling a bit of live active yeast, such as you would use to bake bread at home, on top of the culture and that is supposed to prevent mold.
Sorry Taari, I think you received some misinformation. Baker's yeast = brewer's yeast (although there are different strains for different purposes...I make beer and bread!), and they are definitely active, not inactive. I get both in 'active dry' form that is simply rehydrated (aka proofed) before use. Nutritional yeast (aka nooch) is deactivated (aka inactive, does not 'come back to life') and used as a nutritional ingredient (I like it on salads).
Do you find that your recipe starts to smell after a while? Does it produce lots of flies?
I don't find it smelly; with a good start of maggots or fertile adults (and yeast) it lasts as long and produces as well as any commercial media, IME.