School of Chemical, Biological, and Environmental Engineering, Oregon State University, Corvallis, OR 97331, USA.
Department of Plant and Microbial Biology, North Carolina State University, Raleigh, NC 27695, USA.
J Contam Hydrol. 2021 Jun;240:103796. doi: 10.1016/j.jconhyd.2021.103796. Epub 2021 Mar 13.
Long-term cometabolic transformation of 1,1,1-trichlorethane (1,1,1-TCA) and 1,4-dioxane (1,4-D) was achieved using slow release compounds (SRCs) as growth substrates for pure cultures of Rhodococcus rhodochrous ATCC 21198 (ATCC strain 21198). Resting cell transformation tests showed 1,4-D transformation occurred without a lag phase for cells grown on 2-butanol, while an induction period of several hours was required for 1-butanol grown cells. These observations were consistent with activity-based labeling patterns for monooxygenase hydroxylase components and specific rates of tetrahydrofuran (THF) degradation. 1,1,1-TCA and 1,4-D degradation rates for alcohol-grown cells were slower than those for cells grown on gaseous alkanes such as isobutane. Batch metabolism and degradation tests were performed, in the presence of 1,1,1-TCA and 1,4-D, with the growth of ATCC strain 21198 on alcohols produced by the hydrolysis of orthosilicates. Three orthosilicates were tested: tetrabutylorthosilicate (TBOS), tetra-s-butylorthosilicate (T2BOS), and tetraisopropoxysilane (T2POS). The measured rates of alcohol release in poisoned controls depended on the orthosilicate structure with TBOS, which produced a 1° alcohol (1-butanol), hydrolyzing more rapidly than T2POS and T2BOS, that produced the 2° alcohols 2-butanol and 2-propanol, respectively. The orthosilicates were added as light non-aqueous phase liquids (LNAPLs) with ATCC strain 21198 and formed dispersed droplets when continuously mixed. Continuous rates of oxygen (O) consumption and carbon dioxide (CO) production confirmed alcohol metabolism by ATCC strain 21198 was occurring. The rates of metabolism (TBOS > T2POS > T2BOS) were consistent with the rates of alcohol release via abiotic hydrolysis. 1,4-D and 1,1,1-TCA were continuously transformed in successive additions by ATCC strain 21198 over 125 days, with the rates highly correlated with the rates of metabolism. The metabolism of the alcohols was not inhibited by acetylene, while transformation of 1,4-D and 1,1,1-TCA was inhibited by this gas. As acetylene is a potent inactivator of diverse bacterial monooxygenases, these results suggest that monooxygenase activity was required for the observed cometabolic transformations but not for alcohol utilization. Alcohol concentrations in the biologically active reactors were maintained below the levels of detection, indicating they were metabolized rapidly after being produced. Much lower rates of O consumption were observed in the reactors containing T2BOS, which has benefits for in-situ bioremediation. The results illustrate the importance of the structure of the SRC when developing passive aerobic cometabolic treatment systems.
使用缓慢释放化合物（SRC）作为 Rhodococcus rhodochrous ATCC 21198（ATCC 21198 株）纯培养物的生长基质，实现了 1,1,1-三氯乙烷（1,1,1-TCA）和 1,4-二恶烷（1,4-D）的长期共代谢转化。静止细胞转化试验表明，在 2-丁醇上生长的细胞在没有延迟期的情况下发生 1,4-D 转化，而在 1-丁醇上生长的细胞则需要几个小时的诱导期。这些观察结果与基于活性的单加氧酶羟化酶成分的标记模式和四氢呋喃（THF）的特定降解率一致。在醇上生长的细胞的 1,1,1-TCA 和 1,4-D 降解率比在气态烷烃（如异丁烷）上生长的细胞慢。在存在 1,1,1-TCA 和 1,4-D 的情况下，进行了 ATCC 21198 株在正硅酸酯水解产生的醇上的批量代谢和降解试验。测试了三种正硅酸酯：四丁基原硅酸酯（TBOS）、四仲丁基原硅酸酯（T2BOS）和四异丙基原硅酸酯（T2POS）。在加毒对照中测量的醇释放速率取决于正硅酸酯的结构，其中 TBOS 产生 1°醇（1-丁醇），比 T2POS 和 T2BOS 更快水解，T2POS 和 T2BOS 分别产生 2°醇 2-丁醇和 2-丙醇。正硅酸酯作为轻非水相液体（LNAPLs）添加到 ATCC 21198 株中，并在连续混合时形成分散的液滴。连续的氧气（O）消耗和二氧化碳（CO）产生速率证实 ATCC 21198 株正在进行醇代谢。代谢速率（TBOS > T2POS > T2BOS）与通过非生物水解释放醇的速率一致。在 125 天的时间里，ATCC 21198 株连续转化了 1,4-D 和 1,1,1-TCA 的连续添加物，其速率与代谢速率高度相关。乙炔对醇的代谢没有抑制作用，而 1,4-D 和 1,1,1-TCA 的转化则被该气体抑制。由于乙炔是多种细菌单加氧酶的有效抑制剂，这些结果表明，单加氧酶活性是观察到的共代谢转化所必需的，但不是醇利用所必需的。生物活性反应器中的醇浓度保持在检测水平以下，表明它们在产生后很快被代谢。在含有 T2BOS 的反应器中观察到的 O 消耗速率要低得多，这对原位生物修复有好处。结果表明，在开发被动好氧共代谢处理系统时，SRC 的结构非常重要。
