Extremophile microalgae as feedstock for high‐value carotenoids: A review

There are places in our planet where environmental conditions are beyond normal limits for growth but still harbour life. Extremophile microalgae are the candidates for large‐scale production because (i) their extreme growth conditions help to avoid unwanted contaminations, facilitating their production and (ii) in order to survive under harsh environments, these microorganisms synthesise valuable uncommon biomolecules. Extremophile microalgae include Arthrospira platensis, used as a source of phycocyanin and produced under highly alkaline conditions, and Dunaliella salina, which is industrially produced as a source of β‐carotene and can naturally resist salinity conditions exceeding 300 g L−1. Microalgae can be produced on non‐arable lands, using seawater, and within a wide range of environmental conditions, allowing their production in almost any part of the planet. The current paper aimed at highlighting the biotechnological potential of extremophile microalgae as sources for carotenoids, valuable molecules used as pigments and health‐promoters. Microalgae will play a key role in the future food industry because of their exceptional nutritional and bioactive value. Only a limited number of strains achieved commercial succes. Extremophile microalgae are candidates for large‐scale production because (i) their extreme growth conditions help avoiding unwanted contaminations and (ii) in order to survive under harsh environments, these microorganisms synthesise valuable uncommon biomolecules with potential use in varied high‐end applications. Large‐scale production of extremophile strains can be achieved using tubular photobioreactors but also open systems such as thin‐layer cascade and raceway designs, which are cheaper to operate. Among the many valuable bioactive molecules that microalgae produce, carotenoids (including astaxanthin, lutein, and β‐carotene) are especially relevant for food applications. In this sense, the current manuscript summarises microalgae production strategies and the health‐benefits of consuming microalgae derived carotenoids. Moreover, a number of understudied extremophile strains with potential industrial relevance are also discussed.