The state of Alabama is authorized to become indebted and to sell and issue interest bearing bonds, in addition to all other bonds of the state, in an aggregate principal amount not exceeding $15,000,000.00, the proceeds derived from the sale of said bonds to be used solely for the purpose of paying the expenses incurred in the sale and issuance thereof and for the acquisition, construction, equipment and improvement of state prisons, facilities for the housing, training, education or rehabilitation of prisoners, and other penal and correctional institutions and facilities (including sites therefor) necessary or useful in connection with such prisons and other facilities. None of the proceeds derived from the sale of said bonds may be used to pay rents for the use of real or personal property or to make payments under any lease with option to purchase or similar contractual arrangement. The state of Alabama is also authorized to become indebted and to sell and issue bonds to refund any of the bonds herein authorized, in the amounts (which may exceed the principal amount of the bonds being refunded) and manner as may be specified by the legislature. The bonds shall be sold only at a duly advertised public sale or sales, upon sealed bids or at auction, to the bidder whose bid reflects the lowest total net interest cost to the state for the bonds offered for sale and shall be sold at not less than their face value plus accrued interest thereon. The bonds shall be direct general obligations of the state, and for the prompt and faithful payment of the principal thereof and the interest thereon the full faith and credit of the state are hereby irrevocably pledged. The bonds issued under this amendment and the income therefrom shall be exempt from all taxation in the state. The legislature shall enact appropriate enabling legislation to carry out the intent and purpose of this amendment.