The starch/lipid switch: stress management in microalgae

Microalgae accumulate lipids and starch in high concentrations under ‘stress’ conditions, caused by depletion of nutrients such as nitrogen. These products are of interest as feedstock for sustainable production of commodities such as food, feed, chemicals, materials and biofuels. Under stress conditions, starch and lipids are generally produced at the same time. In order to increase the specific product yields, it would be preferable to produce only lipids or only starch.


In this project we would like to identify the molecular pathways and genetic ‘switch’ in algal metabolism that determines whether lipids or starch are produced. With the insights obtained and by using both metabolic engineering approaches and specific cultivations conditions, we aim to control which compounds are accumulated.


To get insight in the algal nutritional stress response and the specific interaction between starch and lipid accumulation mechanisms, three types of microalgal strains are being studied: a starch producer (Chlamydomonas reinhardtii), a neutral lipid producer (Nannochloropsis sp.) and two hybrid strains (Neochloris oleoabundans and Scenedesmus obliquus) that accumulate both compounds. These species are cultivated in flat panel photobioreactors under lipid-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.

In this project, genetic engineering and bioprocess engineering are used in a complementary way to develop an effective strategy to reliably and accurately control the production and interconversion of starch and lipids.

Thesis Projects

There are various possibilities for doing a BSc or MSc thesis, ranging from projects that involve (photo)bioreactor operation and cultivation strategies, to metabolic modeling, transcriptomics and even genetic engineering. Please note that the minimal prerequisite courses are Process Engineering (BPE-20806) for a BSc thesis, and Microalgae Biotechnology (BPE-32803) and  Bioreactor Design (BPE-21306) for a MSc thesis. Additionally, Metabolic Modelling and Pathway Analysis (BPE-30303) is a prerequisite in case of metabolic modeling. Finally, we assume basic knowledge of molecular biology techniques when you apply for a thesis that involves genetic engineering.

If you are interested in doing a thesis project with us, please send an email or come by, preferably one to three months prior to the start of your thesis. You can start your thesis all year round.


This project is funded by the Chinese Collaboration - Joint Scientific Thematic Research Programme of NWO.

Neochloris oleoabundans_nitrogen conditions.jpg

Figure 1 Neochloris oleoabundans grown under nitrogen replete (A) and nitrogen starved (B) growth conditions. Neutral lipids are stained with a fluorescent dye and show up green, chloroplasts show red autofluorescence.

process optimisation through genetic and bioprocess engineering.jpg

Figure 2 In this project, genetic engineering and bioprocess engineering are used as complementary strategies in process optimisation