## 4 Conclusions  
In this study, we characterized _Cyclotella meneghiiana_ at morphological and molecular levels and determined the physiological parameters affecting the production of fucoxanthin in _Cyclotella meneghiiana_ under varying light levels and nutrient environments. The findings showed that low light (45 umol photons m\({}^{-2}\) s\({}^{-1}\)) and high trace elements yielded the maximum fucoxanthin contents of 7.76 \(\pm\) 0.30 mg g\({}^{-1}\) DW. Consequently, _Cyclotella meneghiiana_ presents as a potentially fucoxanthin-rich resource for the production of durable and cost-effective fucoxanthin.  
The following supporting information can be downloaded at [[https://www.mdpi.com/article/10.3390/app14135504/s1](https://www.mdpi.com/article/10.3390/app14135504/s1)]([https://www.mdpi.com/article/10.3390/app14135504/s1](https://www.mdpi.com/article/10.3390/app14135504/s1)), Figure S1: Phylogram with closely related species constructed using ITS1 sequences of _Cyclotella meneghiiana_ (_Stephanocyclus meneghiiana_). Phylogram was constructed by the neighbor-joining method using the K2P distance protocol in MEGA ver.5.0. Numerical value at the nodes of the branches indicates bootstrap values and asterisks indicate species studied in this study; Figure S2: Fucoxanthin (a-c), \(\beta\)-carotene (d-f), Chlorophyll-a (g-i), Chlorophyll-c (j-l), and Caroenoid (m-o) contents of _C. meneghiiana_ under three light conditions and different nutritional conditions. The vertical bars represented averages \(\pm\) STDEV (\(n=3\)); Table S1: Different nutritional concentrations treatments were used in this study. All other concentrations not indicated were the same as Control group; Table S2: Fucoxanthin content yields from cell density under three light conditions.  
S.C.: Investigation, Methodology. J.C.: Investigation, Methodology, Writing--original draft. Y.L.: Investigation, Methodology. Z.Y.: Conceptualization, Methodology, Supervision. Y.S.: Investigation, Methodology. K.C.: Investigation, Methodology. H.D.: Conceptualization, Methodology, Supervision. W.L.: Conceptualization, Methodology, Supervision. P.L.: Conceptualization, Methodology, Supervision, Writing--review and editing, Funding acquisition. All authors have read and agreed to the published version of the manuscript.  
This research was funded by [Science and Technology Planning Project of Guangdong Province] and [Department of Education of Guangdong Province] grant number [2021B1212050025] and [2022 zdz4008].  
The data of this study are available from the corresponding author upon reasonable request.  
The authors declare no conflicts of interest.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline
**Microalgae** & \
\begin{tabular}{c} **Fucoxanthin Contents** \\ **(mg g\({}^{-1}\) DW)** \\ \end{tabular} &
\begin{tabular}{c} **Sample** \\ **Condition** \\ \end{tabular} & **References** \\ \hline _Cyclotella meneghiiana_ & 7.76 & Dried & In this study \\ _Saccharina japonica_ & 0.03 & [PERSON] & [PERSON] et al., 2017 [26] \\ _Skeletonema costatum_ & 0.36 & [PERSON] & [PERSON] et al., 2017 [26] \\ _Odentella sinensis_ & 1.18 & [PERSON] & [PERSON] et al., 2017 [26] \\ _Nitzschia laevis_ & 1.68 & [PERSON] & [PERSON] et al., 2019 [87] \\ _Isochrysis galbana_ & 2.19 & [PERSON] & [PERSON] et al., 2017 [26] \\ _Chaetoceros gracilis_ & 2.24 & [PERSON] & [PERSON] et al., 2012 [83] \\ _Chaetoceros calcitrans_ & 2.33 & [PERSON] & [PERSON] et al., 2012 [88] \\ _Nitzschia_ sp. & 4.92 & [PERSON] & [PERSON] et al., 2012 [83] \\ _Cylindotheuca closterium_ & 5.23 & [PERSON] & [PERSON] et al., 2011 [89] \\ _Isochrysis galbana_ & 6.04 & [PERSON] & [PERSON] et al., 2012 [83] \\ _Phaeadxylum tricomutum_ & 8.55 & [PERSON] & [PERSON] et al., 2012 [83] \\ _Isochrysis aff. galbana_ & 18.23 & [PERSON] & [PERSON] et al., 2012 [83] \\ _Odentella aurita_ & 21.67 & [PERSON] & [PERSON] et al., 2013 [56] \\ _Isochrysis zlungjiangensis_ & 23.29 & [PERSON] & [PERSON] et al., 2019 [72] \\ \hline \hline \end{tabular}
\end{table}
Table 1: Comparison with fucoxanthin contents in other microalgae.