Photobioreactor
The need to achieve biosynthesis of various products on an industrial scale has driven the development of a range of systems, collectively known as photobioreactors. Photobioreactors are containers that support living organisms, allowing them to carry out various chemical processes, resulting in the production of the desired product (Chen, Yeh et al. 2011, Adessi and De Philippis 2014). Photobioreactors, as distinct from traditional bioreactors, rely on the use of light source to cultivate the photosynthesising organisms contained within the vessel.
There are a large number of different photobioreactors that have been developed, with differences in light sources and intensities, working volumes, mixing techniques, or immobilization techniques, each catering to a particular organism for the production of a particular compound (Adessi and De Philippis 2014). The key to a successful and efficient photobioreactor system is achieving even illumination throughout the reactor vessel (Chen, Yeh et al. 2011). Optimal production of the compound of interest requires optimal illumination of all of the photosynthesising organisms, such that these organisms synthesise their compounds with maximal efficiency. However, as there is an upper limit to the photosynthesising ability of all organisms, coupled with economic considerations owing to the required power input, it is insufficient to simply increase the intensity of the light source employed.
To combat this problem, various photobioreactor systems have been developed, relying on effective mixing of the microorganisms in solution, multiple light sources, and small working volumes. Given that the problem of even illumination increases with larger working volumes, there is an inherent trade-off between photobioreactor efficiency and size, hampering the applicability of many systems for industrial-scale biosynthesis. In addition, the costs of the various components used to construct the photobioreactor (e.g. pumps, light sources) and the required power input for the system need to be considered.
