Meme, until OP pops around, in microbiotics class long ago, we performed tests based on pH of the solution to figure out what the organism was. Meaning each organism has an ideal pH in which it will grow, and out of that zone it will not. Solution can be acid or basic to have this effect. Did this help? Or just muddy the waters?? lol

PS. I use the liquid as it is likely to have good stuff. Im not one to waste anything here, so others may do differently. For example I stir the liquid back into the yogurt.