Fucoxanthin has been receiving ever-increasing interest due to its broad health beneficial effects. Currently, seaweeds are the predominant source of natural fucoxanthin. However, the disappointingly low fucoxanthin content has impeded their use, driving the exploration of alternative fucoxanthin producers. In the present study, thirteen diatom strains were evaluated with respect to growth and fucoxanthin production potential. Cyclotella cryptica (CCMP 333), which grew well for fucoxanthin production under both photoautotrophic and heterotrophic growth conditions, was selected for further investigation. The supply of nitrate and light individually or in combination were all found to promote growth and fucoxanthin accumulation. When transferring heterotrophic cultures to light, fucoxanthin responded differentially to light intensities and was impaired by higher light intensity with a concomitant increase in diadinoxanthin and diatoxanthin, indicative of the modulation of Diadinoxanthin Cycle to cope with the light stress. Taken together, we, for the first time, performed the screening of diatom strains for fucoxanthin production potential and investigated in detail the effect of nutritional and environmental factors on C. cryptica growth and fucoxanthin accumulation. These results provide valuable implications into future engineering of C. cryptica culture parameters for improved fucoxanthin production and C. cryptica may emerge as a promising microalgal source of fucoxanthin.

In recent years, microalgae have drawn increasing attention as a valuable source of functional food ingredients. Intriguingly, Nitzschia laevis is rich in fucoxanthinol that is seldom found in natural sources. Fucoxanthinol, a marine xanthophyll carotenoid, possesses various beneficial bioactivities. Nevertheless, it’s not clear whether fucoxanthinol could exert anti-neuroinflammatory function. In light of these premises, the aim of the present study was to investigate the anti-inflammatory role of fucoxanthinol purified from Nitzschia laevis in Lipopolysaccharide (LPS)-stimulated microglia. The results showed that pre-treatment of fucoxanthinol remarkably attenuated the expression of LPS-induced nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), and the production of tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), prostaglandin E2 (PGE-2), nitric oxide (NO) and reactive oxygen species (ROS) induction. Modulation mechanism studies revealed that fucoxanthinol hampered nuclear factor-kappa B (NF-κB), Akt, and mitogen-activated protein kinase (MAPK) pathways. Meanwhile, fucoxanthinol led to the enhancement of nuclear translocation of NF-E2-related factor 2 (Nrf2), and the upregulation of heme oxygenase-1 (HO-1) and NAD(P)H: quinone oxidoreductase 1 (NQO-1). Taken together, the results indicated that fucoxanthinol obtained from Nitzschia laevis had great potential as a neuroprotective agent in neuroinflammation and neurodegenerative disorders.

Schizochytrium-derived omega-3 polyunsaturated fatty acids (e.g., docosahexaenoic acid (DHA) and eicosapentaenoic acid (EPA)) are proven to be health-beneficial bioactive substances that have been widely applied in the pharmaceutical, nutraceutical, and food industries. In this work, the newly isolated Schizochytrium sp. FJ-1 strain was selected to investigate the effects of salinity on the growth performance, lipid production, DHA yield, and positional distribution of triacylglycerols (TAGs). In addition, Schizochytrium sp. 20888 was used as a control strain. The obtained results showed that Schizochytrium sp. FJ-1 could grow with a low biomass in the absence of sea salt; however, Schizochytrium sp. 20888 did not grow in the medium without sea salt. Moreover, Schizochytrium sp. FJ-1 achieved the highest biomass in 10‰ salinity, whilst Schizochytrium sp. 20888 attained the greatest biomass in 40‰ salinity. In terms of the total lipid content and TAG fraction percentage, Schizochytrium sp. FJ-1 grown in 5–20‰ salinity had high total lipid contents (57.04–60.02%), with TAGs accounting for over 90% of the lipid fraction. The highest DHA contents for total lipids (41.38%) and TAGs (40.18%) were obtained when Schizochytrium sp. FJ-1 was grown under 10‰ salinity conditions. Additionally, under the same culture condition, EPA contents of lipids and TAGs were significantly higher for Schizochytrium sp. FJ-1 compared with Schizochytrium sp. 20888. Furthermore, nuclear magnetic resonance analysis found that the salinity level had a distinct impact on the positional distribution of DHA in TAGs in these two Schizochytrium strains. Schizochytrium sp. FJ-1 grown under 40‰ salinity conditions produced TAGs with the greatest percentage of sn-2 DHA (81.24%). The percentages were higher than those found for the other groups of this microalga and Schizochytrium sp. 20888. Taken together, Schizochytrium sp. FJ-1 could be a potential candidate to produce highly valued DHA lipids or TAG bioproducts by regulating salinity.