Novel Phototrophs for Scaleable and Sustainable Bioprocessing

Phototrophs are attractive bioeconomy actors for biofuels and high-value ingredients. Photoheterotrophy with glycerol addition to the new microalgal strain Dactylococcus dissociatus MT1 can simultaneously increase biomass production and reduce or eliminate the need for gas sparging. This behaviour is modelled mechanistically by linking the oxygen exchange between the cells and the medium as a function of glycerol concentration, cellular chlorophyll content, and photosynthetic efficiency to biomass productivity. The latter is greatest when the photosynthetic and respiratory pathways are nearly balanced. This implies that an intracellular recycling of O₂ and CO₂ increases biomass productivity and that a set-point can be reached which eliminates the need for additional O₂ or CO₂. In the same strain, environmental stressors can induce the production of the carotenoids canthaxanthin, adonixanthin and astaxanthin. The growth and carotenogenesis phases can be initiated, reversed and repeated at regular intervals, thus opening the way to a scalable and sustainable bioprocess.