School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR, USA.
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC, USA.
Sci Total Environ. 2019 Dec 1;694:133688. doi: 10.1016/j.scitotenv.2019.133688. Epub 2019 Jul 30.
Aerobic cometabolism of the emerging contaminant 1,4-dioxane (1,4-D) by isobutane-utilizing microorganisms was assessed in pure culture and aquifer microcosm studies. The bacterium Rhodococcus rhodochrous strain ATCC 21198 transformed low, environmentally-relevant concentrations of 1,4-D when grown on isobutane. Microcosms were constructed with aquifer solids from Fort Carson, Colorado, a site contaminated with 1,4-D and trichloroethene (TCE). Multiple additions of isobutane and 1,4-D over 300 days were transformed in microcosms biostimulated with isobutane and microcosms bioaugmented with strain 21198. Results showed that, over time and with sufficient inorganic nutrients, biostimulation of native microorganisms with isobutane was just as effective as bioaugmentation with strain 21198 to achieve 1,4-D transformation in the microcosms. The presence of TCE at 0.2 mg/L did not inhibit 1,4-D transformation, though TCE itself was not readily transformed. An iterative process was used to determine kinetic parameter values to fit Michaelis-Menten/Monod models to experimental data for simultaneous isobutane utilization, biomass growth, and cometabolic transformation of 1,4-D. Parameter optimization resulted in good model fit to the data over multiple transformations of isobutane and 1,4-D in both short- and long-term experiments. Results suggest low concentrations of 1,4-D studied in the microcosms were cometabolically transformed according to a pseudo first-order rate of 0.37 L/mg TSS/day of 21198. Isobutane consumption was modeled with a maximum rate of 2.58 mg/mg TSS/day and a half saturation constant of 0.09 mg/L. 1,4-D transformation was competitively inhibited by the presence of isobutane and transformation rates were significantly reduced when inorganic nutrients were limiting. Simulations of the repeated additions found a first-order microbial endogenous decay coefficient of 0.03 day fit the alternating periods of active transformation and stagnation between isobutane and 1,4-D additions over approximately one year. The model fitting process highlighted the importance of determining kinetic parameters from data representing low concentrations typically found in the environment.
新兴污染物 1,4-二恶烷（1,4-D）的好氧共代谢作用由利用异丁烷的微生物在纯培养和含水层微宇宙研究中进行了评估。当在异丁烷上生长时，细菌 Rhodococcus rhodochrous 菌株 ATCC 21198 可转化低浓度、具有环境相关性的 1,4-D。微宇宙是用科罗拉多州卡森堡的含水层固体构建的，该地点受到 1,4-D 和三氯乙烯（TCE）的污染。在经过 300 多天的多次异丁烷和 1,4-D 添加后，用异丁烷生物刺激的微宇宙和用菌株 21198 生物增强的微宇宙中转化了多种物质。结果表明，随着时间的推移和足够的无机养分，用异丁烷对本地微生物进行生物刺激与用菌株 21198 进行生物增强一样有效，可在微宇宙中实现 1,4-D 的转化。尽管 TCE 本身不易转化，但 0.2mg/L 的 TCE 存在并没有抑制 1,4-D 的转化。使用迭代过程来确定动力学参数值，以将米氏-门尼兹/单分子模型拟合到实验数据中，以同时利用异丁烷、生物量生长和 1,4-D 的共代谢转化。参数优化导致在短期和长期实验中，对异丁烷和 1,4-D 的多次转化，模型都很好地拟合了数据。结果表明，在微宇宙中研究的低浓度 1,4-D 根据菌株 21198 的 0.37L/mg TSS/天的伪一级反应速率进行共代谢转化。异丁烷消耗用最大速率 2.58mg/mg TSS/天和半饱和常数 0.09mg/L 进行建模。1,4-D 的转化受到异丁烷的竞争抑制，当无机养分受到限制时，转化速率会显著降低。重复添加的模拟发现，符合活性转化和异丁烷与 1,4-D 添加之间停滞交替期的一阶微生物内源性衰减系数为 0.03 天，大约一年时间。模型拟合过程突出了从代表环境中通常发现的低浓度的数据中确定动力学参数的重要性。
