Algaecytes (United Kingdom)

There has been an increasing drive toward better valorising raw biological materials in the context of the sustainability of bio-based industries and the circular economy. As such, microalgae hold the ability to biosynthesise valuable metabolites, which are sought after within the bioenergy, pharmaceuticals, cosmetics or nutrition sectors. Owing to their bioactivities, the xanthophyll pigment fucoxanthin and the omega-3 polyunsaturated fatty acid eicosapentaenoic acid (EPA) have fostered increasing interests in terms of sustainably refining them from natural sources, such as microalgae. Together with the suitability of individual species to industrial cultivation, a key challenge resides in optimizing the yields of these compounds within the microalgal biomass they are retrieved from. The marine diatom Stauroneis sp. LACW24 was batch cultivated into its stationary phase of growth prior to being subjected at high cell density (1 × 106 cells mL-1 ) to seven different regimes of light exposure in replenished medium and under nutritional limitation (silica and nitrate) for 12 days. The highest EPA proportions and yields were obtained under blue LED in f/2 medium (16.5% and 4.8mg g-1 , respectively), double the values obtained under red LED illumination. The fucoxanthin yield was the highest when cells were subjected to blue LEDs (5.9mg g-1 ), a fourfold increase compared to the nitrogen-limited treatment under white LEDs. These results indicate that a two-stage approach to the batch cultivation of this diatom can be used for enhancing the production of the high-value metabolites fucoxanthin and EPA post-stationary phase.

Microalgae accumulate a variety of compounds that form the basis for potential marketable products as whole cell biomass or as fractions after an extraction process. A cascading biorefinery approach aims at recovering and separating multiple algae compounds to valorise the complete biomass and to improve the economics of the value chain. This chapter discusses the extraction, characterisation, and current and potential applications, markets, and legislation surrounding the use of microalgal proteins as food, feed, and functional food products and ingredients.