Tailoring of the biochemical profiles of microalgae by employing mixotrophic cultivation

Mixotrophy, in marine microalgae, is the ability to uptake organic nutrients from the environment, in addition to, or as an alternative to, fixation of carbon through photosynthesis. Many microalgae are capable of mixotrophic and heterotrophic growth, which can be used to maximise culture density, while theoretically lowering production costs compared to photoautotrophy. Here we show that, following screening of three microalgal species for mixotrophic and heterotrophic growth, Tetraselmis suecica and Cyclotella cryptica were capable of mixotrophic growth on glycerol, glucose and acetate and heterotrophically on glucose. Phaeodactylum tricornutum could only be cultured mixotrophically, but when cultured on glycerol cell density increased fourfold compared to photoautotrophic culture. Carbon allocation changed dependent upon carbon source and time of harvesting, with mixotrophic culture of P. tricornutum on glycerol resulting in lower cell length and increased total fatty acid content. These changes can be utilised in the development of a ‘designer alga’.