Physiological and technological considerations for optimising mass algal cultures

The successful coupling between physiology and technology is central to the success of algal biotechnology. Imperative is a proper understanding of the variables and their impacts on biomass and/or biocompound production. The crux lies in photosynthesis and the capturing of light energy at the optimal rate for eventual maximal photochemistry (biosynthesis). It is in the hands of algal biotechnologists to understand the dynamics and regulatory mechanisms of especially PSII (photosystem II) activity in order to advance this technology further. Biophysical and technological optimisation and design aimed at maximising photon flux capture are some of the avenues that needs be pursued. This needs to be augmented by molecular, biochemical and physiological inputs. Unfortunately detailed systematic analyses of the variables, their interaction and possible synergism have rarely been done. The debate regarding the merits and productivity in closed, either plate or tubular, vertical or horizontal, and open pond reactors need to be resolved. Exciting developments regarding online measurements and feedback control for optimal productivities are part of the solutions and approaches that need to be followed. Multistage systems that not only utilise autotrophic growth and stress components, but also combined autotrophic/heterotrophic systems could provide solutions to specific production requirements. These and other important issues are addressed in the overview. The challenges facing algal biotechnologists and future research needs are also discussed.