For the acquiring of rights-of-way, land and property including existing easements, restrictive covenants and reversionary estates necessary for the purposes herein authorized, the board shall have the right and power to acquire the same by purchase, negotiation or condemnation, and should it elect to exercise the right of eminent domain, it may proceed in the manner provided by the general laws of the State of Mississippi for procedure by any county, municipality or corporation organized under the laws of this state, or in any other manner provided by law. The power of eminent domain shall apply not only as to all property of private persons or corporations, but also as to property already devoted to public use including leaseholds, excepting interests in property owned by levee boards, drainage districts, or other flood control agencies. However, the board shall have no authority to acquire without the consent of the owner thereof any property operated and used for port, harbor or industrial purposes or such purposes as the board is authorized to acquire and use property for, unless an actual necessity therefor be alleged and proven. The board is authorized to accept donations of lands, rights therein, monies and materials required for the maintenance or development of any port or harbor. The board may exchange any property or properties acquired under the authority of this chapter for other property or properties usable in carrying out the powers hereby conferred, and also remove from lands needed for its purposes and reconstruct on other locations, buildings, utilities, terminals, railroads or other structures upon the payment of just compensation, if it is necessary so to do in order to carry out any of its plans for port development. The title to all land or property acquired under the authority of this chapter shall vest in the State of Mississippi. Nothing contained in this section shall be construed to authorize the taking by eminent domain of any private property except for necessary public use.