It is sold in a dehydrated form and requires re-hydration before using. TVP may have a rather high fat content, so check the label. It has a pleasant-tasting, cheesy flavor and can be used directly on vegetables, baked potatoes, popcorn and other foods as a condiment. It is different from brewer's yeast or torula yeast. It can often be used by those sensitive to other yeasts.
Yeasts are part of the group fungii.
They were originally considered to be plants even though they do not produce chlorophyll, now they have their own kingdom. Microbial assays for vitamin B12 are no longer considered reliable due to problems with the cross-reactivity of corrinoids. The package lists gelatin, but it is not animal derived. Unfortunately there is no simple answer to this. Many Companies allow individual stores to decide part of their menu, or the ingredients used.