A review on the progress, challenges and prospects in commercializing microalgal fucoxanthin.

Fucoxanthin, the most abundant but nearly untapped carotenoid resource, is in the spotlight in the last decade from various perspectives due to a wide range of bioactivities and healthy benefits. The exploitation of fucoxanthin for nutraceutical and pharmaceutical purposes encompasses enormous scientific and economic potentials. Traditional production of fucoxanthin from brown algae (macroalgae) is constrained by limited yield and prohibitively high cost. Microalgae, as the most diverse photoautotrophs, hold the promises as sustainable sources and ideal cell factories for commercial fucoxanthin production, owing to their rich fucoxanthin content and excellent biomass productivity. In this work, the recent progress in upstream (microalgae selection, optimization of culture conditions, trophic modes, cultivation strategies and biosynthesis pathway) as well as downstream processes (extraction) of fucoxanthin production has been comprehensively and critically reviewed. The major bottlenecks, such as screening of fucoxanthin-producers, conflict between biomass and fucoxanthin accumulation under high light condition, unclear steps in biosynthesis pathway and limited evaluation of outdoor scale-up cultivation and extraction, have been pinpointed. Most importantly, the applications of emerging and conventional techniques facilitating commercialization of microalgal fucoxanthin are highlighted. The reviewed and evaluated include breeding and high-throughput screening methods of elite strains; flashing light effect inducing concurrent biomass and fucoxanthin accumulation; fucoxanthin biosynthesis and the regulatory mechanisms associating with its accumulation elucidated with the development of genetic engineering and omics techniques; and photobioreactors, harvesting and extraction techniques suitable for scaling up fucoxanthin production. In conclusion, the prospects of microalgal fucoxanthin commercialization can be expected with the joint development of fundamental phycology and biotechnology.