Excess CO2 supply inhibits mixotrophic growth of Chlorella protothecoides and Nannochloropsis salina

► Microalgae can grow mixotrophically with substrates cheaper than glucose. ► Glycerol is convenient because is a byproduct of the transesterification reaction in biodiesel production. ► CO2 in excess increases autotrophic microalgae growth, but inhibits the use of organic substrates. ► During night-day light cycle, microalgae exploit glycerol overnight only if CO2 is not in excess. ► Glycerol stimulates a higher lipid accumulation.