Solubilization of beta-carotene in culture media

Several methods were evaluated for the solubilization of supraphysiological concentrations of beta-carotene in culture media. The addition of beta-carotene in ethanol as 0.1% (vol/vol) of culture medium that contained 10% fetal bovine serum and incubation at 37 degrees C for 30 minutes solubilized approximately 50% of the added carotenoid. Solubilized beta-carotene concentrations from 3.06 to 36.4 mumol/l were obtained by this method. Ultracentrifugation studies localized the solubilized beta-carotene to low-density lipoproteins (67.0%) and high-density lipoproteins (24.9%). Other methods utilizing various amounts of fetal bovine serum, ethanol, and hexane as solvents did not significantly improve the solubilization of beta-carotene compared with the use of ethanol as 0.1% (vol/vol) of culture medium that contained 10% fetal bovine serum. Nonetheless, solubilization of supraphysiological concentrations of beta-carotene indicated the feasibility of preparing culture media containing physiological concentrations (approximately 0.5 mumol/l) of beta-carotene.