藻源可溶有机质对17β-雌二醇生物降解的影响

Roles of cyanobacterial-derived dissolved organic matter in mediating biodegradation of 17β-estradiol in water column

为探究藻源可溶有机质(COM)及其生物老化过程对湖泊水体中17β-雌二醇(E2)生物降解的影响特征,通过模拟生物老化,得到5种不同生物活性的COM样品:S0(78%)>S1(67%)>S2(36%)>S3(13%)>S4(1%).结果表明,经过60h的避光培养实验,相同浓度(8mgC/L)的COM样品均提高了微生物群落对E2的一级动力学降解速率,大小顺序为:S0>S4>S3>S1>S2.微生物分析表明,新鲜COM中高活性组分既促进了微生物群落的生长,也维持了较高的群落多样性.而培养期间中、低活性COM组分难以作为微生物的有效碳源,导致微生物量和E2降解速率显著降低.其中,S3和S4处理组中大量累积的芳香族和腐殖质结构可能利于潜在E2降解菌的存活并激发污染物降解酶的表达,进而提高生物量标准化E2降解速率.富营养化水体中雌激素的环境行为和归趋与COM的生物活性密切相关.

The effects of cyanobacterial-derived dissolved organic matter(COM) and its microbial processing on the biodegradation of 17β-estradiol(E2) in lake water column were investigated in this study. Through the simulated microbial ageing within a four-stage plug-flow bioreactor, five COM fractions with a gradient of decreasing bioreactivity were separated: S0(78%) > S1(67%)> S0(36%) > S0(13%) > S0(1%). Within the 60 hours of batch incubation at dark, the addition of COM fractions at 8mgC/L exhibited strong acceleration on E2biodegradation, increasing the first-order kinetic rate with the order of S0 > S4 > S3 > S1 > S2.Microbial analysis further showed that the highly labile compounds in COM not only promoted the bacterial growth but also maintained the diverse microbial community in the S0-amended group. In comparsion, the bacterial concentration and E2biodegradation rate in the S1-and S2-amended groups was remarkably lower, meaning that the semilabile and recalcitrant compounds were unable to serve as effective carbon sources. However, the enriched aromatic, humic structure in the S3-and S4-amended groups significantly increased the biomass-normalized E2biodegradation rate, possibly due to the selection of potentially E2-degrading bacteria and the activation of catabolic enzymes under carbon-limited conditions. The environmental behavior and fate of estrogens in eutrophic waters are closely related to the bioreactivity of COM.