Baranwal Parul, Kang Dae-Wook, Seo Youngwoo
Department of Civil and Environmental Engineering, University of Toledo, Mail Stop 307, 3006 Nitschke Hall, Toledo, OH 43606, United States.
Department of Civil and Environmental Engineering, University of Toledo, Mail Stop 307, 3006 Nitschke Hall, Toledo, OH 43606, United States; Department of Chemical Engineering, University of Toledo, Mail Stop 307, 3048 Nitschke Hall, Toledo, OH 43606, United States.
Sci Total Environ. 2022 Dec 15;852:157993. doi: 10.1016/j.scitotenv.2022.157993. Epub 2022 Aug 12.
The application of bioaugmentation (i.e., injection of contaminant-degrading microorganisms) has shown its potential to remove harmful cyanotoxins like microcystin-LR (MC-LR) from drinking water sources. However, the natural organic matter (NOM) present in both natural and engineered water systems might affect the bacterial biodegradation of MC-LR. Therefore, for the successful application of bioaugmentation for MC-LR removal in water treatment, it is important to understand NOM effects on MC-LR biodegradation. In this study, the impact of NOM [algal organic matter (AOM) and humic substances (HS)] on MC-LR biodegradation was evaluated in the presence of varying concentrations of NOM by monitoring MC-LR biodegradation kinetics. The changes in NOM composition during MC-LR biodegradation were also characterized by a five-component Parallel factor (PARAFAC) model using 336 excitation-emission matrix (EEM) spectra collected at different sampling points. Our results showed decreases in MC-LR biodegradation rate of 1.6-and 3.4-fold in the presence of AOM and HS, respectively. The expression of the functional mlrA gene exhibited a similar trend to the MC-LR degradation rate at different NOM concentrations. EEM-PARAFAC analyses and NOM molecular size fractionation results indicated a relatively greater production of terrestrial humic-like components (57%) and a decrease of protein-like components. Two-dimensional correlation spectroscopy (2D-COS) analyses further confirmed that low molecular weight protein-like components were initially utilized by bacteria, followed by the formation of higher molecular weight humic-like components, likely due to microbial metabolism.
生物强化（即注入能够降解污染物的微生物）已显示出从饮用水源中去除有害蓝藻毒素如微囊藻毒素-LR（MC-LR）的潜力。然而，天然和工程水系统中存在的天然有机物（NOM）可能会影响MC-LR的细菌生物降解。因此，为了在水处理中成功应用生物强化去除MC-LR，了解NOM对MC-LR生物降解的影响非常重要。在本研究中，通过监测MC-LR生物降解动力学，评估了不同浓度NOM（藻类有机物（AOM）和腐殖质（HS））存在下NOM对MC-LR生物降解的影响。还使用在不同采样点收集的336个激发-发射矩阵（EEM）光谱，通过五组分平行因子（PARAFAC）模型对MC-LR生物降解过程中NOM组成的变化进行了表征。我们的结果表明，在存在AOM和HS的情况下，MC-LR生物降解速率分别降低了1.6倍和3.4倍。功能性mlrA基因的表达在不同NOM浓度下呈现出与MC-LR降解速率相似的趋势。EEM-PARAFAC分析和NOM分子大小分级结果表明，陆地腐殖质类成分的产生相对较多（57%），而蛋白质类成分减少。二维相关光谱（2D-COS）分析进一步证实，低分子量蛋白质类成分最初被细菌利用，随后形成高分子量腐殖质类成分，这可能是由于微生物代谢所致。
