Carbohydrate and lipid yield in Microcystis aeruginosa for biofuel production under different light qualities

Biofuels produced from algae have enormous advantages in replacing fossil fuels, and Microcystis aeruginosa has a great potential for biofuel production, due to growing fast to form large amounts of biomass. Light is essential for algal growth, and the optimum light quality can promote the biomass and lipid accumulation for increasing feedstock for biofuel production.

We investigated the biomass accumulation, photosynthetic ability, carbohydrate, and lipid yield as well as related gene expression in M. aeruginosa under red, blue, purple, and white light to promote biofuel production using this alga under the optimal light quality. Compared with white light, purple light promoted the cell growth during the 5 days, while blue light showed inhibitory effect. Red light had no effect on the cell growth, but improved the biomass content to the highest level. Red light improved the photosynthetic ability by raising chlorophyll level, and up-regulating expression of the genes in chlorophyll biosynthesis, photosynthetic electron transfer, and CO₂ fixation. Among these light qualities, red light showed the maximum effect on soluble, insoluble, and total carbohydrate accumulation by up-regulating the genes in polysaccharide and starch formation, and down-regulating the genes in glycolysis and tricarboxylic acid cycle. Red light also exhibited the maximum effect on lipid accumulation, which might be caused by up-regulating five genes in fatty acid biosynthesis.

Red light can promote M. aeruginosa accumulating carbohydrates and lipids by regulating related gene expression, which should be the optimal light quality for improving feedstock yield for biofuel production.