As seen from black beard he absorded, white beard fruit. My theory is that its traps the soul of the person inside his fruit never to get out. You cant eat a too devil fruits wouldnt facing the consequences, there is a 10% percent chance that you will get the devil fruit or smile forever, eating the artificial wont kill you but make you "Smile" and even maybe lose your devil fruit. Because we havent seen an exemple of someone eating too devil fruits.
