The board, acting jointly with the state port authority, is authorized to set aside, or lease all or portions of any lands, roads, docks, sheds, warehouses, elevators, compresses, floating dry docks, graving docks, marine railways, tugboats, or any other necessary or useful improvements constructed or acquired by it to individuals, firms, or corporations, public or private, for port, harbor, commercial or industrial purposes for a period not to exceed ninety-nine years, or to execute a conveyance of sale, except as otherwise limited by law, on such terms and conditions and with such safeguards as would best promote and protect the public interest. Any industrial lease of lands may be executed upon such terms and conditions and for such monetary rental or other consideration as may be found adequate and approved by the board in orders or resolutions authorizing the same. Any covenants and agreements of the lessee to make expenditures in determined amounts, and within such time or times, for improvements to be erected upon the land, by such lessee and to conduct thereon industrial and/or other operations in such aggregate payroll amounts and for such period of time as may be determined and defined in such lease, and to give preference in employment where practical to residents of the State of Mississippi, and to qualified residents of the city and of the county in which such port or harbor is located, shall if included in such lease constitute and be deemed sufficient consideration for the execution of any such lease in the absence of monetary rental or other considerations; and such instrument may contain reasonable provisions giving the lessee the right to remove its or his improvements upon the termination of the lease. All leases theretofore made by any port commission, port authority, or other public agency authorized by law to execute leases for port, harbor, commercial or industrial improvements, which leases are now in effect or which may be hereafter executed by any such public agency or by the board, and all structures and all improvements and other permanent facilities erected, installed or located by such lessees or their successors or assignees within the limits of any port, harbor or part thereof, may be free and exempt from all state, county, and municipal ad valorem taxes if so stipulated in such lease, and for such period as may be fixed in such lease.