Tax liens extinguished when lands revert to state; exception.

Reinstatement of title in the state or its agency shall, by foreclosure or otherwise, operate to extinguish all liens for all taxes or assessments to which the lands would not have been subject had the title been in the state or its agency; provided, however, that any tax certificate or tax deed issued upon such lands or other property in the hands of a person, private firm or private corporation, shall represent a valid obligation against the said lands, and said certificate may be redeemed and paid for by the said state or its agency as provided by law in other cases for the purchase or redemption of tax certificates, and in case of deed, by paying to the holder the amount paid by him or her, plus interest at 6 percent per annum since the date of the said deed.