Abstract: A photo-bioreactor and method of operating are described. The photo-bioreactor includes a reactor vessel arranged to contain a fluid medium within which bio-material is grown, and at least one light-emitting rod extending into the reactor vessel, wherein the light-emitting rod has an elongate tubular member characterized by a length along a longitudinal axis and a width along an axis normal to the longitudinal axis, and designed with an outer wall that encloses one or more light-emitting devices arranged along the longitudinal axis, the outer wall being transparent to at least part of the light emitted by the one or more light-emitting devices into the reactor vessel. The photo-bioreactor further includes a drive system coupled to the elongate tubular member, and operatively configured to rotate the light-emitting rod about the longitudinal axis within reactor vessel, and circulate the fluid medium through the reactor.