## 4 Conclusions  
A novel method was developed for the improved production of carotenoids and other lipids in _Monoraphidium_ sp. by combining multiple abiotic factors. The optimum conditions were identified as 5000 mg:L\({}^{-1}\) N, 250 mg:L\({}^{-1}\) P + K, 70 mg:L\({}^{-1}\) S, 137.5 \(\mu\)mol m\({}^{-2}\) s\({}^{-1}\) LI, and 24 h PP, resulting in a maximum biomass productivity of 75.4 mg:L\({}^{-1}\)d\({}^{-1}\), lipid production of 542.8 mg:L\({}^{-1}\), and total carotenoid production of 16.25 \(\mu\)g:mL\({}^{-1}\). The results suggest that the modulation of abiotic factors has a significant influence on carotenogenesis and lipogenesis, yielding elevated amounts of carotenoids and other lipids, including the five economically significant carotenoids, astaxanthin, violaxanthin, lutein, 9-cis-\(\beta\)-carotene, and \(\beta\)-carotene-5,6-epoxide. These bioactive compounds are valuable to the pharmaceutical and nutraceutical industries. The results showed that lutein content was slightly reduced under optimal conditions while a substantial increase was noted in astaxanthin, violaxanthin, and \(\beta\)-carotene. This study reveals that _Monoraphidium_ sp. is a feasible option for commercial application in the food, feed, and healthcare industries due to its enormous ability to yield carotenoids and other lipids in considerable amounts under optimal conditions. **Supplementary Materials:** The following supporting information can be downloaded at: [[https://www.mdpi.com/article/10.3390/app13106107/s1](https://www.mdpi.com/article/10.3390/app13106107/s1)]([https://www.mdpi.com/article/10.3390/app13106107/s1](https://www.mdpi.com/article/10.3390/app13106107/s1)), Figure S1: Response surface plot with contour lines for biomass productivity (mg L\({}^{-1}\)d\({}^{-1}\)) with varying abiotic stress variable, (a) Nitrogen with Phosphorous and potassium, (b) Nitrogen with Sulphur, (c) Nitrogen with Light Intensity, (d) Nitrogen with Photoperiod, \(\epsilon\) Phosphorous and potassium with Sulphur, (f) Phosphorous and potassium with Light Intensity, (g) Phosphorous and potassium with Photoperiod, (h) Sulphur with Light Intensity, (i) Sulphur with Photoperiod, and (j) Light Intensity with Photoperiod; Figure S2: Response surface plot with contour lines for lipid content (%) with varying abiotic variable, (a) Nitrogen with Phosphorous and potassium, (b) Nitrogen with Sulphur, (c) Nitrogen with Light Intensity, (d) Nitrogen with Photoperiod, (e) Phosphorous and potassium with Sulphur, (f) Phosphorous and potassium with Light Intensity, \begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**S. No.**} & \multicolumn{2}{c}{**Retention Time**} & \multicolumn{2}{c}{**\% Fraction**} & \multicolumn{2}{c}{**Molecular**} & \multirow{2}{*}{**Molecular**} & \multirow{2}{*}{**Abducts**} & \multirow{2}{*}{**Obtained Mass**} \\  & & **(min)** & & & & & **Mass** & & **Formula** & **(Da)** \\ \cline{2-2} \cline{6-9}  & **Control** & **Optimized** & & **Control** & & **Optimized** & & & \\ \hline
1 & 28.07 & 28.07 & 7.8-Didehydroostaxanthin & 14.8 & 17.7 & 594.823 & C\({}_{\mathrm{e}}\)H\({}_{\mathrm{K}}\)O\({}_{\mathrm{A}}\) & M + K\(-\)2H & 631.31 \\
2 & 30.41 & 30.41 & Violaxanthin & 3.61 & 4.85 & 600.870 & C\({}_{\mathrm{e}}\)H\({}_{\mathrm{K}}\)O\({}_{\mathrm{A}}\) & M + H & 599.413 \\
3 & 31.76 & 31.76 & Lutlein \(\beta\)-epoxide & 45.12 & 33.93 & 584.871 & C\({}_{\mathrm{e}}\)H\({}_{\mathrm{K}}\)O\({}_{\mathrm{O}}\) & M + H & 583.41 \\
4 & 33.67 & 33.67 & 9-cis-\(\beta\) caroten & 7.62 & 8.19 & 556.873 & C\({}_{\mathrm{e}}\)H\({}_{\mathrm{K}}\) & M\(-\)H & 599.411 \\
5 & 33.92 & 33.92 & \(\beta\)-carotene-5,6-epoxide & 24.41 & 26.46 & 600.8 & C\({}_{\mathrm{e}}\)H\({}_{\mathrm{K}}\)O\({}_{\mathrm{A}}\) & M\(-\)H & 599.411 \\ \hline \hline \end{tabular}
\end{table}