Can acknowledgement by a notary public be used instead of a medallion signature guarantee?

No, a medallion signature guarantee is not the same as an acknowledgement by a notary public. The medallion signature guarantee is a certification by the institution that the signature is authentic and that the institution accepts liability for any forgery. An acknowledgment is a certification by a notary public attesting that the signer signed a document voluntarily, signed the document in the presence of the notary, and provided proof of identity.