Section 15. Notwithstanding any other provision of law of the contrary, the trustees or officers of a state university designated by them shall have the authority to make any purchase or purchases in the amount of five hundred dollars or less, and to purchase without limitation of amount library books and periodicals, educational and scientific supplies and equipment, printing and binding, emergency repairs and replacement parts, and perishable items, without recourse to any other state board, bureau, department or commission; provided, that in so doing the university shall follow modern methods of purchasing and shall, wherever practicable, invite competitive bids. Except as herein provided, the state purchasing agent shall on the certification of availability of funds purchase all items specified on requisitions submitted to him by such university; provided, that the university shall have the right to review all bids received on university requisitions and to make binding recommendation on the award of the contract based on the judgment of the university as to which of the bids best meet the university's specifications on which the bids were received.