title: Biotransformation of progesterone and norgestrel by two freshwater microalgae (Scenedesmus obliquus and Chlorella pyrenoidosa): transformation kinetics and products identification.
abstract: Natural and synthetic steroid hormones such as progesterone and norgestrel in the aquatic environment may cause adverse effects on aquatic organisms. This study investigated the biotransformation of progesterone and norgestrel in aqueous solutions by two freshwater microalgae Scenedesmus obliquus and Chlorella pyrenoidosa and elucidated their transformation mechanisms. More than 95% of progesterone was transformed by the two microalgae within 5d. For norgestrel, almost complete transformation by S. obliquus was observed after 5 d, but nearly 40% was remained when incubated with C. pyrenoidosa. The results also showed that these two compounds were not accumulated in the algal cells. Biotransformation was found to be the main mechanism for their loss in the aqueous solutions, and it followed the first-order kinetic model. For progesterone, three main transformation products, i.e. 3β-hydroxy-5α-pregnan-20-one, 3,20-allopregnanedione and 1,4-pregnadiene-3,20-dione, and six minor androgens were identified. For norgestrel, only two transformation products, 4,5-dihydronorgestrel and 6,7-dehydronorgestrel, were identified for the first time. Hydroxylation, reduction and oxidation are proposed to be the main transformation pathways. Among the two microalgae species, S. obliquus was found more efficient in the transformation of the two target compounds than C. pyrenoidosa. The results clearly demonstrated the capability of the two microalgae to transform the two progestogens. The biotransformation and products could have significant environmental implications in the fate and effects of the two steroids.
authors.affiliation: State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
authors.forename: Fu-Qiang
authors.initials: FQ
authors.lastname: Peng
authors.forename: Guang-Guo
authors.initials: GG
authors.lastname: Ying
authors.forename: Bin
authors.initials: B
authors.lastname: Yang
authors.forename: Shan
authors.initials: S
authors.lastname: Liu
authors.forename: Hua-Jie
authors.initials: HJ
authors.lastname: Lai
authors.forename: You-Sheng
authors.initials: YS
authors.lastname: Liu
authors.forename: Zhi-Feng
authors.initials: ZF
authors.lastname: Chen
authors.forename: Guang-Jie
authors.initials: GJ
authors.lastname: Zhou
mesh_terms: D001711:Biotransformation; D002708:Chlorella / Q000378:metabolism*; D005618:Fresh Water / Q000737:chemistry; D007700:Kinetics; D058086:Microalgae; D009644:Norgestrel / Q000378:metabolism*; D011374:Progesterone / Q000378:metabolism*; D044444:Scenedesmus / Q000378:metabolism*; D014874:Water Pollutants, Chemical / Q000378:metabolism*
chemical_list: D014874:Water Pollutants, Chemical; D009644:Norgestrel; D011374:Progesterone
keywords: Algae; Biotransformation; Norgestrel; Progesterone; Transformation products