We, basically, no.
Brain tanned leather, specifically Buckskin has the grain, ie, epidermus removed so it is a so called "split", the portion between layers of skin. You would have to remove the grain, epidermus, however commercial tanning changes the fiberous make up of the skin by the use of acids and chemicals, rather than just coatng each and every fiber with oils, the brain is 99% fats, of any type of imulsified oils. I'm not sure what you would use to bleach it, chlorine will destroy the hides. Peroxyde might work?