Microalgae are photosynthetic microorganisms mostly grown autotrophically, which means that light energy is used to convert CO2 into organic compounds while O2 is released as a by-product. Some microalgae can also be grown heterotrophically, in which organic carbons, such as sugars and organic acids, are used as carbon sources in the absence of light. In this trophic mode, O2 is consumed and CO2 is released as a by-product. Autotrophic and heterotrophic cultivation of microalgae can be combined in mixotrophic cultivation.
In this thesis we designed a novel mixotrophic process called “oxygen balanced mixotrophy” in which there is no net O2 production. This was possible by tuning the supply of organic carbon to the rate of photosynthesis. Oxygen balanced mixotrophy does not require any aeration, about 90% of the organic carbon provided is converted into biomass and only 10% is lost as CO2, and biomass productivity doubled its autotrophic counterpart.