If you just want a simple fermented cheese I use the same ones I make soy yogurt with. 50 billion
If you're looking to do a more fancy, cultured cheese like roquefort then some kind of pennicilin, which I know nothing about
Roquefort is made with any of the blue-green fungi, of the genus penicillium.
Penicillin is a pharmaceutical drug which is also derived from the fungi and it's not used in cheese making.
I've never tasted cultured vegan cheese (too expensive) so have not idea if they taste anything like dairy. However, Roquefort has a very unique salty taste and has quite a crumbly texture.
Cheese making is quite fascinating. I'm going to try and make some as I bought a starter but still have to use it.
Make vegan cheese with our real, but vegan, cheese starters. This starter contains a protective bacterium and gas-forming bacteria.