Building Better Bio-Beads: Engineering Modulation of pH and Metabolite Diffusive Flux in Hydrogels

氯化有机溶剂是美国地下水中最常见的污染物。这些化合物对供水的污染对公众健康构成了重大风险，因为其中几种化合物是已知的致癌物质，可能会导致通过饮用水接触。虽然工程师已经开发出利用微生物将这些污染物作为食物消耗的能力的处理技术，但这个过程可能会导致有害酸的产生，最终导致活动停止。这项拟议的研究将把这些有益的微生物保护在名为生物珠的保护性胶囊中。这些胶囊将允许有益的微生物在生产清洁水的同时继续消耗氯化有机溶剂。这些生物小球可以与不同的微生物一起使用，以解决许多环境问题，并在许多其他领域得到应用，包括药物输送、制药、食品加工和废水处理。这个项目将通过将研究纳入传统的本科实验室课程来增加本科学习的机会。如果成功，该项目将有助于保护国家的水安全，并确保美国公众获得安全的饮用水。三氯乙烯和四氯乙烯等氯化有机溶剂(TCE和PCE)是美国地下水中最常见的污染物。这些化合物对供水的污染对公众健康构成重大风险，因为其中几种化合物是已知的致癌物质，可通过饮用水暴露。虽然像PCE这样的化合物可以通过低成本的厌氧还原二氯化反应来破坏，但这种过程会降低pH，导致积累更多的可溶性、挥发性和危险的降解产物。微生物通过多种内部途径抵抗pH变化，包括质子外流和控制膜通透性以限制运输。不幸的是，这些pH控制方法是以新陈代谢能量和微生物的最佳生长为代价的。这项建议的目的是利用生物微胶囊化、有机-无机杂化材料科学和传质理论的现有基本概念，解决目前氯化溶剂生物修复中pH控制的不足。这项研究将包括建造一种生物微珠，目标是自我调节pH。生物微珠环境将被设计成模仿和改进微生物自然使用的pH和运输控制机制。生物微球包埋的最终目标是在非理想的外部pH梯度中扩大包埋生物的活性代谢范围。这种生物微珠的设计将通过将生物灵感机制融入到分层胶囊设计中来实现，方法是增加缓冲组以控制内部pH，调整静电结构电荷以限制带电物种的传输，以及部署旨在外流或与外部光刺激驱动的质子发生反应的催化层。这项研究将被数百名从事相关的、积极的学习的一年级本科生科学家的组合力量所利用，以提供有价值的数据来实现项目目标。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

Chlorinated organic solvents are the most common pollutants in groundwater in the U.S. Pollution of water supplies by these compounds represent a significant risk to public health, as several are known carcinogens that can result in exposure through drinking water. While engineers have developed treatment technology that uses the ability of microbes to consume these pollutants as food, the process can result in the production of harmful acids that eventually halts activity. The proposed research will shield these beneficial microbes in protective capsules called biobeads. These capsules will allow the beneficial microbes to continue to consume chlorinated organic solvents while producing clean water. These biobeads can be used with different microbes to address many environmental problems, with applications in many other fields including drug delivery, pharmaceuticals, food processing, and wastewater treatment. This project will augment undergraduate learning opportunities by incorporating the research into traditional undergraduate laboratory courses. If successful, this project will help protect the Nation's water security and ensure safe drinking water availability to the U.S. public. Chlorinated organic solvents like tri- and per-chloroethene (TCE and PCE) are the most common pollutants in groundwater in the U.S. Pollution of water supplies by these compounds represent a significant risk to public health, as several are known carcinogens that can result in exposure through drinking water. While compounds like PCE can be destroyed through low cost, anaerobic reductive dichlorination, this process can lower pH, resulting in the accumulation of more soluble, volatile, and hazardous degradation products. Microorganisms resist pH change through a variety of internal means, including proton efflux and control of membrane permeability to restrict transport. Unfortunately, these pH control methods come at the cost of metabolic energy and optimal growth of the microorganism. The objective of this proposal is to address the current deficiency of pH control in bioremediation of chlorinated solvents by leveraging existing fundamental concepts from biological microencapsulation, hybrid organic-inorganic material science, and mass transport theory. The research will involve building a biobead with the goal of self-regulated pH control. The biobead environment will be designed to emulate and improve on pH and transport control mechanisms naturally employed by microorganisms. The ultimate goal of biobead encapsulation is to extend the range of active metabolism for the encapsulated organism in non-ideal external pH gradients. This biobead design will be accomplished through incorporation of bioinspired mechanisms into a layered capsule design via addition of buffer groups to control internal pH, adjustment of electrostatic structural charges to restrict charged species transport, and deployment of catalytic layers designed to efflux or react with protons driven by external photic stimuli. The research will be leveraged by the combinatorial power of hundreds of first-year undergraduate student scientists engaged in relevant, active learning to provide valuable data to achieve project objectives.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.