I think the one I buy uses corn starch. So my cheese is GMO.
Its possible, don’t know your brand, but Cellulose is a common anti-caking agent.... Other things can be used, but they can affect taste etc in various ways. Cellulose is very common as an anti-caking agent and pre shredded cheese nearly always has some sort of anti-caking agent added to it.
What percentage of the overall volume is typical I don’t know, but the idea you can get pre shredded cheese to remain shredded while sitting in a bag for days or weeks without adding something to keep it from sticking back together, unless you froze each individual shred and kept them frozen until you used it, which I don’t think most consumers would be game to, is silly.
Its an anti caking agent, nothing nefarious at all.