If no person shall redeem the lands sold for taxes prior to the expiration of the right to redeem, at the expiration thereof, and on production of the certificate of purchase and upon proof satisfactory to the collector that a purchaser or his or her heirs, successors, or assigns are authorized to acquire the deed, the collector of the county in which the sale of such lands took place shall execute to the purchaser, his or her heirs or assigns, in the name of the state, a conveyance of the real estate so sold, which shall vest in the grantee an absolute estate in fee simple, subject, however, to all claims thereon for unpaid taxes except such unpaid taxes existing at time of the purchase of said lands and the lien for which taxes was inferior to the lien for taxes for which said tract or lot of land was sold.