## 4 Conclusions  
In summary, the present study investigated the impact of red light (R) and a red light shift to full spectrum (RS) on _P. tricornutum_ cell growth, biomass, and lipid production. The introduction of the RS during the beginning of the stationary phase in the cultures of _P. tricornutum_ had a positive impact on both biomass and lipid production. This is due to the favorable light pattern, as red light-acclimated cells during the lag and exponential phases provide better conditions for cellular and development processes and white light during the stationary phase helps in the accumulation of more lipids as compared to a single spectrum of light. It was also discovered that the specific light wavelength R and RS had an impact on regulating the level of polyunsaturated fatty acids (PUFAs), specifically the omega-3 fatty acid eicosapentaenoic acid (20:5 n-3). Moreover, a light shift can be an effective system to reduce the negative effects of self-shading and the proper distribution of light in large-scale photobioreactors. However, more detailed studies on photosystems and metabolite distribution in time-scale patterns are necessary to bring more clarity about wavelength shifts and lipid accumulation. In addition, the experiment is easily replicable and scalable in developing countries with fewer resources. This system has the potential to be used to enhance the productivity while reducing the loss of biomass because of potentially excessive heat generation and self-shading due to high-density cultures. The acclimation and light shift studies for different species of microalgae  
\begin{table}
\begin{tabular}{l c c c c c} \hline \hline
**Physical Properties** & **W** & **R** & **RS** & **EN 14214:2008** & **ASTM D6751** \\ \hline density & 0.749 & 0.728 & 0.719 & 0.860–0.900 & 0.875–0.900 \\ iodine value & 122.5 & 118.4 & 121.6 & \textless{}120 & - \\ cetane number & 49.6 & 51.4 & 51.2 & \textgreater{}51 & \textgreater{}47 \\ viscosity & 2.7 & 2.6 & 2.6 & 3.5–5.0 & 1.9–6.0 \\ \hline \hline \end{tabular}
\end{table}
Table 5: Values of physical properties of biodiesel related to the fatty acid compositions in each culture conditions (W, R, and RS) compared to the International Standard ASTM and EN14214.  
such as diatoms, in both autotrophic and mixotrophic conditions, will open new avenues for algal biotechnology to help produce a wide range of special metabolites.  
Conceptualization, N.S.; F.M.-M.; H.G., and L.D.-P.; methodology, N.S.; F.A.; F.M.-M.; H.G. and I.D.-P.; validation, N.S.; G.F.; F.A.; M.C.; S.M.B.; F.M.-M.; H.G., and I.D.-P.; formal analysis, N.S.; F.A.; F.M.-M. and I.D.-P. investigation, N.S.; G.F.; and F.A.; writing--original draft preparation, N.S.; F.A.; F.M.-M. and I.D.-P.; writing--review and editing, N.S.; G.F.; F.A.; M.C.; F.M.-M.; S.M.B.; H.G. and I.D.-P.; supervision, H.G. and I.D.-P.; project administration, I.D.-P.; funding acquisition, I.D.-P. All authors have read and agreed to the published version of the manuscript.  
This research was funded by the Natural Sciences and Engineering Research Council of Canada--Engage grant reference no CRDPJ/530085-18 to IDP. All students (N.S., G.F., and M.C.) and postdoctoral fellows (F.A.) are supported by Mitacs--Acceleration program grant no IT12310 to IDP.  
The authors wish to thank the industrial collaborator [PERSON], PhD and Algae-C for sample and support. [PERSON] from Western University is acknowledged for providing the diatom culture. Additionally, a very special thanks to [PERSON] and [PERSON] from UQTR for their precious discussion and information on confocal microscopy and photosynthesis respectively.  
The authors declare no conflict of interest.