Monitoring dihydrodiol polyaromatic hydrocarbon metabolites produced by the freshwater microalgae Selenastrum capricornutum.
We found that microalgae exposed to a mixture of polycyclic aromatic hydrocarbons (PAHs) did not show growth inhibition. Thus, we assumed that they could metabolize these compounds. In this study, the dihydrodiol-type PAH metabolites of benzo(a)pyrene (BaP), benzo(a)anthracene (BaA), benzo(b)fluoranthene (BbF) and benzo(k)fluoranthene (BkF) produced by the freshwater microalgae Selenastrum capricornutum were monitored and quantified using high-performance liquid chromatography with fluorescence detection (HPLC-FD) techniques. Exposure bioassays with S. capricornutum were performed using a 266 ng mL(-1) mixture of PAHs at different exposure times (0.75, 1, 3, 8, 16, 24 and 48 h) under controlled temperature (25 °C); the dihydrodiol metabolites formed in the liquid medium and the biomass were quantified. Metabolite identities were confirmed using HPLC-mass spectrometry; most of the metabolites formed were derived from BaA degradation. At 48 h after exposure 5,6-dBaA and 8,9-dBaA/10,11-dBaA were present in the liquid medium at 20% and 67% of the initial mass of BaA, respectively. Three metabolites of BaP were monitored in the liquid medium and biomass and, at 24 h, 4,5-dBaP accounted for 19%; , 7,8-dBaP, 5%; and 9,10-dBaP, 5% relative to the initial BaP mass. Microalgae exposed to BbF showed the presence of 1,2-dBbF and 9,10-dBbF (at 0.3% and 0.1% of the initial BbF mass, respectively) and those exposed to BkF produced 8,9-dBkF (6.5% of the initial BkF mass) in the liquid medium. Seven unknown compounds were formed after exposure; two compounds were identified as the metabolites of BaA and BaP. The results could facilitate the elucidation of the controversial biodegradation mechanism in microalgae.
Facultad de Química, Departamento de Química Analítica, Universidad Nacional Autónoma de México, Ciudad Universitaria, México. D. F., 04510, Mexico.
Fernando José
FJ
Hernández Blanco
Facultad de Química, Departamento de Química Analítica, Universidad Nacional Autónoma de México, Ciudad Universitaria, México. D. F., 04510, Mexico. Electronic address: pgcllas@unam.mx.
Martha Patricia
MP
García de Llasera
D001564:Benzo(a)pyrene / Q000032:analysis*; D001673:Biodegradation, Environmental; D001681:Biological Assay; D018533:Biomass; D000460:Chlorophyta / Q000378:metabolism*; D002851:Chromatography, High Pressure Liquid; D004784:Environmental Monitoring / Q000379:methods*; D005449:Fluorenes / Q000032:analysis; D005618:Fresh Water; D058086:Microalgae / Q000378:metabolism*; D009281:Naphthalenes / Q000032:analysis; D011084:Polycyclic Aromatic Hydrocarbons / Q000032:analysis; D015203:Reproducibility of Results; D014871:Water Microbiology
D005449:Fluorenes; D009281:Naphthalenes; D011084:Polycyclic Aromatic Hydrocarbons; C507866:trans-1,2-dihydro-1,2-naphthalenediol; D001564:Benzo(a)pyrene; C006703:benzo(b)fluoranthene; C022921:benzo(k)fluoranthene
Dihydrodiol metabolites; HPLC-FD; PAHs biodegradation; Selenastrum capricornutum