Scale-down of microalgae cultivations in tubular photo-bioreactors--a conceptual approach

Rational design of large-scale bioreactors is still suffering from inadequate scale-up of technical parameters from lab to large scale and from missing kinetic information concerning the physiological reactions of the specific strain under cultivation. Therefore, simulations of processes expected in large-scale have to be carried out as far as possible and experiments have to be performed in small-scale reactors mimicking the situation in large scale. This procedure is referred to as scale-down. In this paper a concept to accomplish this task is proposed. Firstly, interactions between light transfer, fluid dynamics, and microbial metabolism are described. Secondly, a procedure is given to decompose the interactions by simulation on the one hand and by finding physiological parameters in model reactors on the other. Light transfer can be calculated by Monte Carlo methods, while fluid dynamics is handled by CFD. Ideally illuminated model photo-bioreactors and pilot reactors with enforced flow field are proposed to measure physiological parameters especially induced by light/dark cycles generated by interaction of turbulences and light attenuation.