Both starch (a typical microalgal carbohydrate) and triacylglycerol (TAG, a typical microalgal lipid) can serve as a raw material for the sustainable production of commodities such as food, feed, chemicals, materials and biofuels. Under ‘stress’ conditions, caused by depletion of nutrients such as nitrogen, microalgae accumulate starch and TAG in high concentrations. However, both compounds are often produced at imultaneously. In order to increase the specific product yields, it would be preferable to produce only lipids or only starch.
In this project, Algal Genetic Switches Which Induce Triglycerides and/or Carbohydrates production for Human nutrition, we are identifying the molecular pathways and genetic ‘switches’ in algal metabolism that determines whether and when starch or TAG are produced. With the insights obtained and by using both metabolic engineering approaches and cultivation optimisation, we aim to accurately control the production and interconversion of starch and TAG.
Three types of microalgal strains are being studied in this project: a starch producer (Chlamydomonas reinhardtii), a TAG producer (Nannochloropsis sp.) and two hybrid strains (Neochloris oleoabundans and Scenedesmus obliquus) that accumulate both compounds. These species are cultivated in controlled photobioreactors under TAG and starch accumulation inducing growth conditions. A combination of metabolic modeling and transcriptomics is used to obtain insight in the interaction of the starch and lipid metabolic pathways in these microalgal strains. Metabolic engineering will be applied in these microalgae for over-expression, knockdown or knockout of identified key genes and regulators of lipid and starch accumulation and conversion.
Creating metabolic and genetic insights
We cultivate microalgae under controlled laboratory conditions. Under these conditions, we induce starch and TAG accumulation and measure production and consumption rates of all important metabolites, substrates and products. We develop metabolic models and measure gene expression, to evaluate the effect of cultivation conditions on the algal metabolism.
We create mutant or engineered strains, to obtain insight in the starch and TAG pathways and ultimately, to control the accumulation of these compounds.
We are testing various cultivation strategies under simulated outdoor conditions, that could be used to enhanced the production of starch and/or TAG.