Apparently almost any strain of lactobacillus should be able to make some type of yogurt (each one with a distinct flavor). I have taken relatively expensive probiotic supplements sold in a very famous supermarket in the US known for this type of thing (yes, that one), which claim to have close to a dozen strains of lactobacillus. It was utterly incapable of even beginning to make yogurt. It was just plain milk at the end of the process, not even a discernible yogurty taste to it. On the other hand, we had great success using a cheap yogurt starter we found sitting around that had expired 5 years ago. I would love to have a full spectrum of probiotics, but can't spend the money to actually find one that works, so I have to stick to homemade yogurt.