  In this paper we study a bilinear optimal control problem associated to a 3D
chemo-repulsion model with linear production. We prove the existence of weak
solutions and we establish a regularity criterion to get global in time strong
solutions. As a consequence, we deduce the existence of a global optimal
solution with bilinear control and, using a Lagrange multipliers theorem, we
derive first-order optimality conditions for local optimal solutions.
