Development of Passive and Sustainable Cometabolic Systems to Treat Complex Contaminant Mixtures by Encapsulating Microbial Cultures and Slow Release Substrates in Hydrogels

挥发性有机化合物（VOCs）污染地下水是一个普遍的问题， 美国的从98个主要饮用水采集的3500多个地下水样品中， 1985-2001年的供水含水层至少含有一种人为污染物，并检测到VOCs 最常见的。在检测到的前15种VOCs中，有8种是氯化脂肪烃（CAH）： 氯仿（CF）、全氯乙烯（PCE）、三氯乙烯（TCE）、1，1，1-三氯乙烷（1，1，1-TCA）、 顺式-1，2-二氯乙烯（cis-DCE），反式-1，2-二氯乙烯（trans-DCE），二氯甲烷（DCM）， 和1，1-二氯乙烷（1，1-DCA）。所有这些CAH都被疾病控制中心列出， 预防可能是人类致癌物。越来越令人担忧的是新出现的共同污染物，如 1，4-二氧六环（1，4-D），这也是一种可能的人类致癌物质。常见的补救技术，如 作为泵送和处理，对于处理从低浓度缓慢扩散的污染物混合物是不可持续的。 地下的渗透带。这些问题突出了长期、被动和 经济补救技术。 被动和可持续的系统提出了新出现的污染物，如 1，4-D与CAH混合。这些被动系统将通过共同封装无菌 细菌培养物与水凝胶珠中的缓释化合物（SRC）。SRC会慢慢水解 在珠粒中产生醇，其将作为微生物生长基质和作为诱导剂， 非特异性污染物降解单加氧酶。地下水污染物会扩散到 水凝胶中，它们将共代谢转化为无毒产品。在初步研究中， 将烷烃氧化细菌紫红红球菌ATCC 21198与 结冷胶水凝胶中的正硅酸盐SRC。1，1，1-TCA、cis-DCE和1，4-D的连续降解 维持了300多天。在拟议的工作中，这种模式细菌的蛋白质组学分析将 进行鉴定活性单加氧酶和表征酶和生理 这些变化最终限制了这种细菌在包封系统中的长期活性。基因组- 还将使用使能的方法来合理地鉴定具有不同生物学特性的其他微生物。 单加氧酶互补物，其也可以与SRC共包封以实现单加氧酶互补物的降解。 一系列新出现的污染物。材料科学研究将决定如何生产水凝胶 珠保持机械完整性较长的时间，专注于过程，可以很容易地 按比例放大以生产原位处理所需的大量珠粒。这些珠子将被用于 在实验室规模的不同平台中，以创建被动渗透反应屏障。水凝胶 微珠还可用于处理被污染的土壤和沉积物以及其他新出现的污染物。

Groundwater contamination with volatile organic compounds (VOCs) is a widespread issue throughout the United States. Over 50% of more than 3500 groundwater samples collected from 98 major drinking water supply aquifers from 1985-2001 contained at least one anthropogenic contaminant, with VOCs detected most frequently. Among the top 15 VOCs detected, eight were chlorinated aliphatic hydrocarbons (CAHs): chloroform (CF), perchloroethylene (PCE), trichloroethylene (TCE), 1,1,1-trichloroethane (1,1,1-TCA), cis-1,2-dichloroethylene (cis-DCE), trans-1,2-dichloroethylene (trans-DCE), dichloromethane (DCM), and 1,1-dichloroethane (1,1-DCA). All of these CAHs are listed by the Centers for Disease Control and Prevention as being likely human carcinogens. Of increasing concern are emerging co-contaminants, such as 1,4-dioxane (1,4-D), which is also a likely human carcinogen. Common remediation techniques, such as pump-and-treat, are not sustainable for treating contaminant mixtures that slowly diffuse from low permeability zones in the subsurface. These issues highlight the need for long-term, passive, and economical remediation techniques. Passive and sustainable systems are proposed for the aerobic cometabolism of emerging contaminants, such as 1,4-D, that are mixed with CAHs. These passive systems will be created by co-encapsulating axenic bacterial cultures with a slow release compound (SRC) in hydrogel beads. The SRC will slowly hydrolyze in the beads to produce an alcohol, which will serve as a microbial growth substrate and as an inducer for non-specific contaminant-degrading monooxygenases. Groundwater contaminants will diffuse into the hydrogels where they will be cometabolically transformed to non-toxic products. In preliminary studies, the alkane-oxidizing bacterium Rhodococcus rhodochrous ATCC 21198 was co-encapsulated with an orthosilicate SRC in a gellan gum hydrogel. Continuous degradation of 1,1,1-TCA, cis-DCE, and 1,4-D was maintained for over 300 days. In the proposed work, proteomic analyses of this model bacterium will be performed to identify the active monooxygenases and to characterize the enzymatic and physiological changes that ultimately limit the long-term activity of this bacterium in the encapsulated systems. Genome- enabled approaches will also be used to rationally identify other microorganisms with different monooxygenase compliments that can also be co-encapsulated with SRCs to achieve the degradation of a broad range of emerging contaminants. Material science research will determine how to produce hydrogels beads that maintain mechanical integrity for extended periods, focusing on processes that can be easily scaled-up for producing large quantities of beads needed for in-situ treatment. The beads will then be used in different platforms at the laboratory scale to create passive permeable reactive barriers. The hydrogel beads might also be used for treating contaminated soils and sediments and other emerging contaminants.