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Background: Carotenoids are biological antioxidants and play important roles in protecting the body from diseases and aging. Canthaxanthin is one of the most widely used carotenoids in the industry and medicine. This study aimed to investigate the biological properties of canthaxanthin pigment as well as its production optimization in a low-cost medium using a radioresistant microbial strain named Dietzia maris.
Materials and methods: Bacterial carotenoids were extracted and its antibacterial, anti-tumor, and cytotoxicity properties were investigated. Then, the effect of Krebs intermediates and pH on the production of pigment and microbial biomass in the whey medium was investigated using the response surface methodology.
Results: Maximum pigment production was found to be 92/54 mg/l in whey culture medium at pH 8 and in the presence of 12.5 mM of each of citrate, glutamate, malate, and succinate by the response surface method. The pigment did not show any cytotoxic effect on Hela, HFB, and MCF-7 cell lines. Besides, the pigment did not have any antibacterial properties.
Conclusion: Radioresistant microbial strains are better candidates for microbial pigment production due to their stability and high antioxidant activity. In this study, a whey culture medium was used to reduce the production cost of canthaxanthin. The addition of Krebs intermediaries in the fermentation medium increased the pigment production by Dietzia maris significantly.

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This study showed the potential of the electrospinning (in this case electrospraying) technique to produce whey protein concentrate (WPC) micro and nanocapsules for applications in the encapsulation of canthaxanthin. The results showed that the solution concentration, feed solution flow rate and applied voltage had a direct effect  on the encapsulation efficiency. by increasing of the solution concentration, feed solution flow rate and applied voltage, the encapsulation efficiency increased. The results showed that solution concentration was the most effective factor in electrospraying, because its scale estimate was highest. According to the results of analysis of variance (ANOVA) for this model, the regression model suggested a significant value for both linear and quadratic terms at P < 0.05. Also in order to obtain 0.93% encapsulation efficiency, optimum  point was found at the emulsion concentration of 39.4%, feed solution flow rate of 12.2 ml/min, applied voltage of 17.5 kV, and 17.1cm distance between needle tip and collector.