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Fucoxanthin is a natural active substance derived from diatoms that is beneficial to the growth and immunity of humans and aquatic animals. Temperature, light and salinity are important environmental factors affecting the accumulation of diatom actives; however, their effects on the production of fucoxanthin in C. weissflogii are unclear. In this study, single-factor experiments are designed and followed by an orthogonal experiment to determine the optimal combination of fucoxanthin production conditions in C. weissflogii. The results showed that the optimum conditions for fucoxanthin production were a temperature of 30 °C, a light intensity of 30 umol m[sup.−2] s[sup.−1] and a salinity of 25. Under these conditions, the cell density, biomass, carotenoid content and fucoxanthin content of C. weissflogii reached 1.97 × 10[sup.6] cell mL[sup.−1] , 0.76 g L[sup.−1] , 2.209 mg L[sup.−1] and 1.372 mg g[sup.−1] , respectively, which were increased to 1.53, 1.71, 2.50 and 1.48 times higher than their initial content. The work sought to give useful information that will lead to an improved understanding of the effective method of cultivation of C. weissflogii for natural fucoxanthin production.

Fucoxanthin (Fx) has been proven to exert numerous biological properties, which makes it an interesting molecule with diverse industrial applications. In this study, the kinetic behavior of Fx was studied to optimize three variables: time (t—3 min to 7 days), temperature (T—5 to 85 °C), and concentration of ethanol in water (S—50 to 100%, v/v), in order to obtain the best Fx yield from Undaria pinnatifida using conventional heat extraction. The Fx content (Y[sub.1] ) was found through HPLC-DAD and expressed in µg Fx/g of algae sample dry weight (AS dw). Furthermore, extraction yield (Y[sub.2] ) was also found through dry weight analysis and was expressed in mg extract (E)/g AS dw. The purity of the extracts (Y[sub.3] ) was found and expressed in mg Fx/g E dw. The optimal conditions selected for Y[sub.1] were T = 45 °C, S = 70%, and t = 66 min, obtaining ~5.24 mg Fx/g AS; for Y[sub.2] were T = 65 °C, S = 60%, and t = ~10 min, obtaining ~450 mg E/g AS; and for Y[sub.3] were T = 45 °C, S = 70%, and t = 45 min, obtaining ~12.3 mg Fx/g E. In addition, for the selected optimums, a full screening of pigments was performed by HPLC-DAD, while phenolics and flavonoids were quantified by spectrophotometric techniques and several biological properties were evaluated (namely, antioxidant, antimicrobial, and cholinesterase inhibitory activity). These results could be of interest for future applications in the food, cosmetic, or pharmaceutical industries, as they show the Fx kinetic behavior and could help reduce costs associated with energy and solvent consumption while maximizing the extraction yields.

Acne vulgaris, a chronic inflammatory skin disorder, represents a pivotal research area in dermatology. Although fucoxanthin, a marine-derived carotenoid, displays potent anti-inflammatory activity, its therapeutic potential in acne pathogenesis remains underexplored. This study investigates fucoxanthin's effects on Propionibacterium acnes (P.acnes)-induced auricular inflammation in mice, focusing on its modulation of the I[kappa]B[alpha]/NF-[kappa]B signaling axis and inhibition of NF-[kappa]B nuclear translocation. Inflammation in the ear of mice was induced using a P.acnes injection model. The anti-inflammatory effects of fucoxanthin were verified by evaluating the levels of erythema, pathological damage, and inflammatory factors in the mice ear. An in vitro model was constructed to explore the regulatory mechanism of IkappaBalpha (I[kappa]B[alpha])/nuclear factor-kappaB (NF-[kappa]B) pathway by fucoxanthin. Fucoxanthin alleviated P. acnes-induced inflammatory pathology, reducing ear erythema. Mechanistically, it preserved I[kappa]B[alpha] stability, suppressed NF-[kappa]B nuclear translocation, and decreased proinflammatory cytokine production. Fucoxanthin exerts anti-acne effects through coordinated inhibition of I[kappa]B[alpha] degradation and NF-[kappa]B nuclear translocation, establishing its potential as a targeted therapeutic agent for inflammatory acne.

A switch from a petroleum-based to a biobased economy requires the capacity to produce both high-value low-volume and low-value high-volume products. Recent evidence supports the development of microalgae-based microbial cell factories with the objective of establishing environmentally sustainable manufacturing solutions. Diatoms display rich diversity and potential in this regard. We focus on Phaeodactylum tricornutum, a pennate diatom that is commonly found in marine ecosystems, and discuss recent trends in developing the diatom chassis for the production of a suite of natural and genetically engineered products. Both upstream and downstream developments are reviewed for the commercial development of P. tricornutum as a cell factory for a spectrum of marketable products. P. tricornutum CCAP 1055/1 is a diatom with a sequenced annotated genome with >100 000 expression sequence tags. Transformation is becoming routine using biolistics, electroporation, and more recently by conjugation with E. coli. There is improved understanding of its biochemical pathways.P. tricornutum is showcased as a microalgal cell factory with a product spectrum including eicosapentaenoic acid, fucoxanthin, neutral lipids, and crysolaminarin, all producible with the chassis, in addition to heterologous recombinant proteins, triterpenoids (lupeol and betulin), and bioplastics precursors.P. tricornutum can be readily harvested with a host of approaches, and relevant products can be recovered using green extraction processes such as microwave-assisted and pressurized liquid extraction, with the potential to develop sustainable cost-effective processes in a biorefinery approach.

Fucoxanthin (FX), a primary carotenoid, is associated with the fucoxanthin-chlorophyll a/c binding protein (FCP) complex integrated into the thylakoid membrane (TM) which functions as a light-harvesting complex in the diatom Phaeodactylum tricornutum. Here, we aimed to elucidate the FX production regulated by different light intensities via the correlation of FX biosynthesis and apoproteins composing of FCP complex. High light (HL) accelerated P. tricornutum growth more than low light (LL). The maximum values of FX content and productivity obtained under LL (1.7 mg g−1 and 2.12 mg L−1 day−1, respectively) were substantially higher than those obtained under HL (0.54 mg g−1 and 0.79 mg L−1 day−1, respectively). Notably, proteome and photosynthetic pigment analyses revealed the enrichment of FCP antennae in the LL culture TM fractions but not the HL culture. Semi-quantification of FCP antenna protein using LC–MS/MS and RNA transcriptome analyses revealed that PtLhcf5 and PtLhcf8 played crucial roles in FCP biosynthesis under LL. P. tricornutum cultured under light transition exhibited FCP formation only in the early growth stage to meet the increased photosynthetic activity requirements under LL. Meanwhile, FCP degradation could be triggered by HL throughout the cultivation period. Therefore, FX production was highly correlated with FCP formation, and LL conditions in the early growth stage were critical for higher FX productivity.

Photosynthetic organisms must balance maximizing productive light absorption and protecting themselves from too much light, which causes damage. Both tasks require pigments—chlorophylls and carotenoids—which absorb light energy and either transfer it to photosystems or disperse it as heat. Wang et al. determined the structure of a fucoxanthin chlorophyll a/c–binding protein (FCP) from a diatom. The structure reveals the arrangement of the specialized photosynthetic pigments in this light-harvesting protein. Fucoxanthin and chlorophyll c absorb the blue-green light that penetrates to deeper water and is not absorbed well by chlorophylls a or b. FCPs are related to the light-harvesting complexes of plants but have more binding sites for carotenoids and fewer for chlorophylls, which may help transfer and disperse light energy. Science , this issue p. eaav0365 Specialized pigments held together by a protein scaffold help diatoms harvest a broad spectrum of light. Diatoms are abundant photosynthetic organisms in aquatic environments and contribute 40% of its primary productivity. An important factor that contributes to the success of diatoms is their fucoxanthin chlorophyll a/c-binding proteins (FCPs), which have exceptional light-harvesting and photoprotection capabilities. Here, we report the crystal structure of an FCP from the marine diatom Phaeodactylum tricornutum , which reveals the binding of seven chlorophylls (Chls) a, two Chls c, seven fucoxanthins (Fxs), and probably one diadinoxanthin within the protein scaffold. Efficient energy transfer pathways can be found between Chl a and c, and each Fx is surrounded by Chls, enabling the energy transfer and quenching via Fx highly efficient. The structure provides a basis for elucidating the mechanisms of blue-green light harvesting, energy transfer, and dissipation in diatoms.

Diatoms are ubiquitous photosynthetic microorganisms with great potential for biotechnological applications. However, their commercialisation is hampered by production costs, requiring hence optimisation of cultivation methods. Phytohormones are plant growth regulators which may be used to influence physiological processes in microalgae, including diatoms. In this study, the model species Phaeodactylum tricornutum ( Phaeodactylaceae ) and two Irish isolates of Stauroneis sp. ( Stauroneidaceae ) and Nitzschia sp. ( Bacillariaceae ) were grown with varying amounts of the phytohormones indoleacetic acid (IAA), gibberellic acid (GA3), methyl jasmonate (MJ), abscisic acid (ABA) or salicylic acid (SA), and their influence on pigment and fatty acid profiles was monitored. The application of GA3 (200 mg/l) stimulated the growth of P. tricornutum which accumulated 52% more dry biomass compared to the control and concomitantly returned the highest eicosapentaenoic acid (EPA) yield (0.6 mg/l). The highest fucoxanthin yield (0.18 mg/l) was obtained for P. tricornutum cultivated with GA3 (2 mg/l) supplementation. In Stauroneis sp., SA (1 mg/l) had the most positive effect on EPA, the content of which was enhanced up to 45.7 μg/mg (4.6% of total dry weight). The SA (1 mg/l) treatment also boosted carotenogenesis in Nitzschia sp., leading to 1.7- and 14-fold increases in fucoxanthin and β-carotene compared to the control, respectively. Of note, MJ (0.5 mg/l) increased the EPA content of all diatom species compared to their controls. These results indicate that phytohormone-based treatments can be used to alter the pigment and lipid content of microalgae, which tend to respond in dose- and species-specific manners to individual compounds. Key points • Response to phytohormones was investigated in diatoms from distinct families . • MJ (0.5 mg/l) caused an increase in EPA cellular content in all three diatoms . • Phytohormones mostly caused dose-dependent and species-specific responses .

We observed differences in lhc classification in Chromista. We proposed a classification of the lhcf family with two groups specific to haptophytes, one specific to diatoms, and one specific to seaweeds. Identification and characterization of the Fucoxanthin and Chlorophyll a/c -binding Protein (FCP) of the haptophyte microalgae Tisochrysis lutea were performed by similarity analysis. The FCP family contains 52 lhc genes in T. lutea . FCP pigment binding site candidates were characterized on Lhcf protein monomers of T. lutea , which possesses at least nine chlorophylls and five fucoxanthin molecules, on average, per monomer. The expression of T. lutea lhc genes was assessed during turbidostat and chemostat experiments, one with constant light (CL) and changing nitrogen phases, the second with a 12 h:12 h sinusoidal photoperiod and changing nitrogen phases. RNA-seq analysis revealed a dynamic decrease in the expression of lhc genes with nitrogen depletion. We observed that T. lutea lhcx2 was only expressed at night, suggesting that its role is to protect \\cells from return of light after prolonged darkness exposure.

The light conditions are of utmost importance in any microalgae production process especially involving artificial illumination. This also applies to a chrysolaminarin (soluble 1,3‐β‐glucan) production process using the diatom Phaeodactylum tricornutum. Here we examine the influence of the amount of light per gram biomass (specific light availability) and the influence of two different biomass densities (at the same amount of light per gram biomass) on the accumulation of the storage product chrysolaminarin during nitrogen depletion in artificially illuminated flat‐panel airlift photobioreactors. Besides chrysolaminarin, other compounds (fucoxanthin, fatty acids used for energy storage [C16 fatty acids], and eicosapentaenoic acid) are regarded as well. Our results show that the time course of C‐allocation between chrysolaminarin and fatty acids, serving as storage compounds, is influenced by specific light availability and cell concentration. Furthermore, our findings demonstrate that with increasing specific light availability, the maximal chrysolaminarin content increases. However, this effect is limited. Beyond a certain specific light availability (here: 5 µmolphotons gDW−1 s−1) the maximal chrysolaminarin content no longer increases, but the rate of increase becomes faster. Furthermore, the conversion of light to chrysolaminarin is best at the beginning of nitrogen depletion. Additionally, our results show that a high biomass concentration has a negative effect on the maximal chrysolaminarin content, most likely due to the occurring self‐shading effects. Here we examine the influence of the amount of light per gram biomass (specific light availability) and the influence of two different biomass densities (at the same amount of light per gram biomass) on the accumulation of the storage product chrysolaminarin and potential co‐products: fucoxanthin, eicosapentaenoic acid, and fatty acids used for energy storage (C16 fatty acids), during nitrogen depletion in artificially illuminated flat panel airlift photobioreactors. Our results show that the time course of C‐allocation between chrysolaminarin and fatty acids as storage compounds depends on specific light availability and cell concentration.

Fucoxanthin and fatty acids are active substances that are beneficial to the growth and immunity of humans and aquatic animals. However, relatively few species have been exploited for fucoxanthin and fatty acids in the industry. At the same time, due to its low extract content, poor stability, high production cost, and serious seasonal and regional limitations, the industry cannot normally meet the greater demand of the international market. Therefore, this experiment seeks to improve the fucoxanthin and fatty acid content of C. weissflogii by adjusting the nitrogen concentration in the culture medium. It was found that when the nitrogen concentration was 150 mg L[sup.−1] , the cell number was 1.5 × 10[sup.6] cell mL[sup.−1] , and the average biomass was 0.75 g L[sup.−1] . The mean value of carotenoid concentration was 2.179 mg L[sup.−1] . The average concentration of fucoxanthin was 1.547 mg g[sup.−1] . When the nitrogen concentration was 75 mg L[sup.−1] , the fatty acid content reached its highest. By adjusting the concentration of nitrogen, the contents of fucoxanthin and fatty acids were increased. The results provided a theoretical basis for commercial extraction of fucoxanthin and fatty acids and further promoted the industrialization of fucoxanthin and fatty acids.