Diverting the carbon flow from GAP by genetic modification to some product, away from the natural flow toward cell synthesis, will usually lower the organisms’ fitness. The living cell contains complex regulatory networks that function in concert to tune metabolic activity to the environmental conditions, and to respond appropriately when conditions change. Therefore, the physiological effects of genetically introducing a metabolic pathway into a microbe are extremely difficult to predict and it should be realized that the introduction of (a set of) genes is only the very first step. Controllable and stable expression demands thorough understanding of the organism’s genetic, regulatory, and metabolic makeup. Only then one can interfere successfully with cellular activities toward optimal biofuel formation. The information
necessary relates to growth demands, adaptive mechanisms, physiology, and regulation at all omics levels. Obviously then, the choice of organism to use as a production platform in a Photanol approach should be guided by our level of knowledge of the organism