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

地下水中挥发性有机化合物(VOCs)污染是一个普遍存在的问题 美国。从98个主要饮用水中采集的3500多个地下水样本中，超过50% 1985-2001年期间的补给含水层至少含有一种人为污染物，检测到挥发性有机化合物 最频繁的。在检测到的前15种VOCs中，有8种是氯化脂肪族碳氢化合物(CAHs)： 氯仿(CF)、四氯乙烯(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-1，2-DCE)、二氯甲烷(DCM)、 和1，1-二氯乙烷(1，1-DCA)。所有这些CAH都是由疾病控制中心和 预防可能是人类致癌物质。越来越令人担忧的是正在出现的共同污染物，如 1，4-二恶烷(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 作为泵和处理，是不可持续的处理污染物混合物缓慢扩散从低 地下的渗透带。这些问题突出表明，需要长期、被动和 经济的补救技术。 对于新出现的污染物的有氧共代谢，提出了被动和可持续的系统，如 作为1，4-D，它们与CAHs混合。这些被动系统将通过共同封装无菌素来创建 在水凝胶微珠中使用缓释化合物(SRC)进行细菌培养。SRC将缓慢地水解 在珠子中产生酒精，酒精将作为微生物生长的底物和诱导剂 非特异性污染物降解单加氧酶。地下水污染物将扩散到 在水凝胶中，它们将被共代谢转化为无毒产品。在初步研究中， 将烷烃氧化菌红球菌atcc 21198与一种 结冷胶水凝胶中的正硅酸盐SRC。1，1，1-三氯乙酸、顺式二氯乙烯和1，4-D的连续降解 保持了300多天。在拟议的工作中，对这种模式细菌的蛋白质组学分析将 对活性单加氧酶进行鉴定，并对酶和生理特性进行表征 最终限制这种细菌在封装系统中长期活动的变化。基因组- 启用的方法也将被用来合理地识别具有不同 单加氧酶，也可以与SRCs共包裹，以实现对 新出现的污染物种类繁多。材料科学研究将决定如何生产水凝胶 长时间保持机械完整性的珠子，重点放在容易实现的工艺上 放大生产原位处理所需的大量珠子。然后，这些珠子将被使用 在实验室规模的不同平台上创建被动渗透性反应屏障。水凝胶 微珠也可用于处理受污染的土壤、沉积物和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.