Abstract
BackgroundMarine diatoms have a higher fucoxanthin content in comparison to macroalgae. Fucoxanthin features many potent bioactive properties, particularly anti-obesity properties. Despite the great potential for harvesting larger amounts of fucoxanthin, the impacts of light quality (light source, intensity, and photoperiod) on fucoxanthin production and the essential proteins involved in fucoxanthin biosynthesis in marine diatoms remain unclear.ResultsIn the present study, Cylindrotheca closterium was selected from four different species of diatoms based on its high fucoxanthin content and productivity. Optimal light conditions (light source, intensity, and regime) were determined by a “Design of Experiment” approach (software MODDE Pro 11 was used). The model indicated that an 18/6 light/darkness regime increased fucoxanthin productivity remarkably as opposed to a 12/12 or 24/0 regime. Eventually, blue light-emitting diode light, as an alternative to fluorescent light, at 100 μmol/m2/s and 18/6 light/darkness regime yielded maximum fucoxanthin productivity and minimal energy consumption. The fucoxanthin production of C. closterium under the predicted optimal light conditions was assessed both in bottle and bag photobioreactors (PBRs). The high fucoxanthin content (25.5 mg/g) obtained from bag PBRs demonstrated the feasibility of large-scale production. The proteomes of C. closterium under the most favorable and unfavorable fucoxanthin biosynthesis light/darkness regimes (18/6 and 24/0, respectively) were compared to identify the essential proteins associated with fucoxanthin accumulation by matrix-assisted laser desorption/ionization-time of flight–mass spectrometry. Six proteins that were up-regulated in the 18/6 regime but down-regulated in the 24/0 were identified as important chloroplastic proteins involved in photosynthesis, energy metabolism, and cellular processes.ConclusionsBlue light-emitting diode light at 100 μmol/m2/s and 18/6 light/darkness regime induced maximum fucoxanthin productivity in C. closterium and minimized energy consumption. The high fucoxanthin production in the bag photobioreactor under optimal light conditions demonstrated the possibility of commercialization. Proteomics suggests that fucoxanthin biosynthesis is intimately associated with the photosynthetic efficiency of the diatom, providing another technical and bioengineering outlook on fucoxanthin enhancement.
Highlights
Marine diatoms have a higher fucoxanthin content in comparison to macroalgae
With 95% confidence interval overlapped, no difference was found between fluorescent light and the two types of Light-emitting diode (LED) lights with respect to fucoxanthin content, as illustrated in Fig. 2a at 100 μmol/m2/s and 18/6 light regime, though different spectra of light were emitted by the three different light sources
A photoperiod of 24 h substantially suppresses the accumulation of fucoxanthin content with blue LED light at 100 μmol/m2/s, whereas 12/12 and 18/6 illumination cycles were favorable for fucoxanthin synthesis in C. closterium (Fig. 2c)
Summary
Marine diatoms have a higher fucoxanthin content in comparison to macroalgae. Diatoms constitute an important autotrophic functional group in the marine food web [2]. Diatoms, besides their ecological and geochemical functions, are receiving increasing attention because of their potential use in biodiesel production [3] and for pharmaceutical purposes [4]. Diatoms are abundant in bioactive metabolites such as antibacterial polyunsaturated fatty acids, i.e. eicosapentaenoic acid [5], and photosynthetic accessory pigments, such as fucoxanthin, both of which have been heavily investigated over the last several decades [6]. Its additional characteristic of rapid sedimentation became beneficial for reducing the harvesting cost
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