Biotransformation and bioconcentration of steroid estrogens by Chlorella vulgaris

Abstract

The biotransformation and bioconcentration of natural and synthetic steroid estrogens by Chlorella vulgaris were investigated using batch shaking experiments with incubation for 48 hours in the light or dark. Estradiol and estrone were inter-convertible in both light and dark conditions, however this biotransformation showed a preference to estrone. In the light, 50% of estradiol was further metabolized to an unknown product. Apart from biotransformation, estrone as well as hydroxyestrone, estriol and ethinylestradiol were relatively stable in the algal culture, while estradiol valerate was hydrolyzed to estradiol and then estrone within 3 hours of incubation. All the tested estrogens exhibited a degree of partitioning to C. vulgaris, however, the concentrations of estriol, hydroxyestrone, ethinylestradiol and estradiol valerate were always below the quantification limits. For estradiol and estrone, the partitioning of these estrogens in the algal extracts to the filtrates was below 6% of the total present. The average concentration factor for estrone was around 27, however the concentration factor for estradiol is not reported since no equilibrium was reached between aqueous solution and that within the cells due to continuing biotransformation.