Optimization of media components for enhanced carotenoid production by Paracoccus marcusii RSPO1 and assessment of their cytotoxicity against A549 and vero cells.

In this study, we tried to explore the influence of various tricarboxylic acid (TCA) cycle intermediates on carotenoid production and with a focus on enhancing pigment biosynthesis, we conducted two statistical analysis. In case of TCA intermediates influence on pigment production by Paracoccus marcusii RSPO1; fumaric acid, and malic acid were observed as potent enhancers of pigment biosynthesis. Further, to optimize key media components for enhanced carotenoid production, the Plackett-Burman design was employed encompassing carbon, nitrogen sources, TCA cycle intermediates, and metal salts. The selected factors after Plackett Burman were fine-tuned through Response Surface Methodology and the optimal concentrations that have remarkably elevated carotenoid production were starch-2.24 g/l, MgSO ₄ -0.416 g/l, ZnSO ₄ -0.0157 g/l, and fumaric Acid-16 mM. Further, evaluation of pigment cytotoxicity against normal (Vero) and Non-Small Cell Carcinoma (A549) cells was performed. The resultant IC ₅₀ values were quantified as 161.3 µg/ml and 7.623 µg/ml for Vero and A549 cells, respectively. Moreover, a reactive oxygen species (ROS) determination study in A549 cells was done which have shown a noteworthy threefold ROS production in A549 cells through fluorescence spectroscopic observation. This implies that the bacterial carotenoids can act as potent pro-oxidants against cancerous cells while being nontoxic toward normal cells.