MICROALGAE BIOREFINERY FOR A GREENER ECONOMY

Microalgae are photosynthetic microorganisms that can grow quickly while converting carbon dioxide into oxygen and biomass. Notably, they also produce a large variety of metabolites of interest, such as lipids, polyphenols, proteins and vitamins. Moreover, thanks to the presence of an overall negative charge on the surface of the cell wall, microalgae biomass itself is a promising material for the removal of heavy metals from contaminated water. Among microalgae, some groups present unique characteristics: for example, the diatoms produce a porous silica cell wall that is itself a promising material. Thanks to these characteristics, microalgae can be used for different applications for a greener economy, such as feed for aquaculture, as ingredients in beauty products and to produce biostimulants. Interestingly, changes in environmental conditions (light quality and quantity, salinity, nutrient concentration) can lead to a biomass enriched in specific compounds. Changes in light quality and quantity have been reported to affect both pigment profile and growth, with red light having a positive effect on biomass production in some microalgae, while blue light increases lipid production in other species. Moreover, while most algae have an autotrophic metabolism and use carbon dioxide as a carbon source, some microalgae can also use organic matter (such as glucose or glycerol) changing their metabolism to mixotrophy, with positive effects on growth and biomass production. Understanding the effects of these different cultivation parameters and their interactions on microalgae growth and metabolite production is important for finding sustainable solutions for a sustainable future.