The initial fermentation procedures to generate collagenase or other bacterial enzymes required the use of mammalian meat peptones that contained collagen peptides. As collagenase fermentation methods were refined, gelatin peptones were used in place of meat peptones. You can request a certificate of origin from the manufacturer to determine if animal proteins were used in the fermentation or manufacturing process.
Products labeled AOF means no animal products were used in the fermentation procedure to generate collagenase or neutral protease. The absence of animal products in the manufacturing procedure avoids providing additional explanations to regulatory authorities on the potential threat of an adventitious agent contaminating the product.