The carbon partitioning of glucose and DIC in mixotrophic, heterotrophic and photoautotrophic cultures of Tetraselmis suecica

Abstract

Objective Changes in the partitioning of dissolved inorganic (DIC) and glucose were elucidated by utilising ¹³C labelled DIC or glucose, and quantifying the biochemical profile of mixotrophic, heterotrophic and photoautotrophic cultures of the microalga Tetraselmis suecica. Results Mixotrophic cultivation increases microalgal productivity and changes their biochemical profile, due to an alteration in the partitioning of carbon within the cell. When cultured mixotrophically and heterotrophically, there is enhanced incorporation of carbon into shorter chain saturated fatty acids and non-lipid biomass, compared to photoautotrophic cultivation. Autotrophic culture results in increased total fatty acid content of cultures (4.19% dry weight compared to 2.13%) and shifts the fatty acid profile in favour of long-chain unsaturated fatty acids, such as 18:2 n-(9,12), compared to mixotrophic culture. Quantifying the changes in partitioning between DIC and glucose facilitates tailoring of the biochemical profile to develop “designer” algae. Conclusions There is a condition specific shift in carbon partitioning into different fatty acid and biochemical fractions in T. suecica, with more inorganic carbon partitioned into 18:2 n-(9,12) in photoautotrophic rather than mixotrophic cultures.