Microalgae-Based Biorefineries: Challenges and Future Trends to Produce Carbohydrate Enriched Biomass, High-Added Value Products and Bioactive Compounds

Abstract

Microalgae have demonstrated a large potential in biotechnology as a source of various macromolecules (proteins, carbohydrates, and lipids) and high-added value products (pigments, poly-unsaturated fatty acids, peptides, exo-polysaccharides, etc.). The production of biomass at a large scale becomes more economically feasible when it is part of a biorefinery designed within the circular economy concept. Thus, the aim of this critical review is to highlight and discuss challenges and future trends related to the multi-product microalgae-based biorefineries, including both phototrophic and mixotrophic cultures treating wastewater and the recovery of biomass as a source of valuable macromolecules and high-added and low-value products (biofertilizers and biostimulants). The therapeutic properties of some microalgae-bioactive compounds are also discussed. Novel trends such as the screening of species for antimicrobial compounds, the production of bioplastics using wastewater, the circular economy strategy, and the need for more Life Cycle Assessment studies (LCA) are suggested as some of the future research lines.

Enhancing the biochemical growth of Haematococcus pluvialis by mitigation of broad-spectrum light stress in wastewater cultures

“…Different formulas were used for the calculation of different chlorophylls and carotenoids as shown in eqn ( 2)- (5).…”

“…[1][2][3][4] Their biomass is capable to build up a notable quantity of these compounds and can be used in nutraceutical, pharmaceutical, and cosmetics industries besides being a reservoir of biofuel. [4][5][6] They produce astaxanthin, which is known as the 'king of ketocarotenoids' and has stormed the commercial market with its price shooting to 2.57 billion US$ in 2025 which can reach up to 3.4 billion US$ by 2027. 1,[7][8][9] However, the factors that play a role in controlling the growth of H. pluvialis, metabolism, and biochemical composition for producing value-added products are temperature, pH, light intensity, and nutrient availability.…”

Laboratory- and Pilot-Scale Cultivation of Tetraselmis striata to Produce Valuable Metabolic Compounds

“…Microalgae are very important photosynthetic microorganisms that have demonstrated their great biotechnological potential as sources of valuable metabolic compounds, including proteins, carbohydrates, lipids, pigments, polyunsaturated fatty acids (PUFAs) and peptides [ 1 ]. These compounds are mainly used in the food industry as well as in the pharmaceutical, nutraceutical and biofuel sectors [ 2 ].…”

“…(filamentous cyanobacterium), Chlorella sp., Dunaliella sp., Haematococcus sp., Tetraselmis sp. and Nannochloropsis sp., as the production costs are still the main barrier [ 1 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. However, their cultivation can be economically feasible when their growth is part of a biorefinery and biomass is exploited to its full potential [ 1 ].…”

“…and Nannochloropsis sp., as the production costs are still the main barrier [ 1 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 ]. However, their cultivation can be economically feasible when their growth is part of a biorefinery and biomass is exploited to its full potential [ 1 ]. Marine microalgae can further reduce cultivation costs as in scaled-up cultures water requirements are exceptionally high favoring the use of seawater [ 5 ].…”