Impacts of phosphorus availability on lipid production by Chlamydomonas reinhardtii

The high cost of production of algal biofuel raises questions about its practical implementation on an industrial scale. Increasing the oil productivity of algae and using cheap growth medium are good ways of resolving this issue. A large research effort directed into this area shows that limiting the nitrogen source in the media increases cellular lipid levels. Much less attention has been given to the role of phosphorus nutrition in relation to lipid production, and even less focus is given to the role of phosphorus starvation. Our studies show that exposing cultures of the chlorophyte alga Chlamydomonas reinhardtii to phosphorus starvation resulted in elevated levels of lipids, which then decreased when phosphorus was made available again. Respiration rates were higher in the absence of phosphorus starvation and increased further on the resupply of phosphorus. No difference in photosynthetic parameters and lipid productivity was observed due to the absence of phosphorus. The absence of phosphorus increases the lipid content of a cell significantly but decreases the biomass and therefore the overall lipid productivity remains the same. Although P-limitation/starvation may not improve the overall lipid yield it may help reduce the cost of production involved in growth media and downstream processing.