Living Reverse Osmosis Membranes: Engineered Membrane Biofilms that Control Their Own Thickness, Prevent Biofouling and Degrade Contaminants

1402063 KumarLiving反渗透膜：控制自身厚度的工程膜生物膜，防止生物污染和降解污染物反渗透（RO）膜正被用于净化替代水源，如回收废水，苦咸水和海水。 该技术是理想的，因为它可以去除几乎所有溶解在水中的物质，包括盐，微生物污染物和有机污染物。然而，采用RO膜的主要挑战是伴随这些膜结垢的能量增加。 污垢是不需要的物质在固体表面上的积聚，从而损害功能。污垢材料可以由活生物体（生物或生物污垢）或非活物质（无机或有机）组成。特别是，由沉积引起的生物结垢，然后称为生物膜的菌落中的微生物的生长，是一个主要的挑战。 由于RO膜对化学消毒剂的敏感性，生物膜难以防止，并且一旦形成就极难通过当前的化学清洁方法消除。 在该项目中，生物膜的持久性将用于通过工程生物膜来解决生物污染问题，该工程生物膜1）控制其自身的厚度和2）释放分子（信号），以防止其他微生物对该工程生物膜的定殖。 这种生物膜也将被工程化以有助于去除可以通过RO膜的污染物。通过激活一系列遗传途径（即，分泌酶以除去将细菌固定在适当位置并使细菌游走的聚合物）迄今尚未被提出用于RO生物污垢控制。因此，该提议的新颖特征是使用代谢工程来产生包括RO膜和薄的有益生物膜的第一活性膜，其将防止生物结垢以及去除水回收系统中的有毒废物。为了控制有益生物膜的范围，PI将利用E。大肠杆菌具有一种新的二鸟苷酸环化酶（c-di-GMP）结合蛋白BdcA。 PI已经设计了BdcA以引起生物膜分散。通过控制BdcA的产生，可以限制有益生物膜形成生物膜的程度。PI还建议证明，有可能在这些有益的生物膜细菌中掺入污染物降解酶，以增强对柠檬酸盐化合物的去除。通过控制反渗透膜上的生物膜，将消除消毒和清洁所需的化学品，并将这一关键水处理技术的总功耗降至最低。这项工作在获得关于如何控制生物膜形成以用于工程应用的见解方面也很重要，并且它可以为控制生物膜形成以治疗慢性疾病提供见解。 为此，每年至少培训两名本科生，并努力招募代表性不足的群体。研究结果将通过YouTube以专业拍摄的教学视频的形式传播给不同的受众。最后，正在进行的中学生水科学和教育营，在宾夕法尼亚州立大学流行的科学U计划的一部分，将从一个为期三天的计划扩大到一个星期，并将开发一个新的膜研究生课程。

1402063KumarLiving Reverse Osmosis Membranes: Engineered Membrane Biofilms that Control Their Own Thickness, Prevent Biofouling and Degrade ContaminantsReverse Osmosis (RO) membranes are being used to purify alternative sources of water such as recycled wastewater, brackish water and seawater. This technology is ideal as it can remove almost all substances dissolved in water including salt, microbial contaminants and organic contaminants. However, a major challenge to employing RO membranes is the increase in energy that accompanies fouling of these membranes. Fouling is the accumulation of unwanted material on solid surfaces to the detriment of function. The fouling material can consist of either living organisms (biological or biofouling) or a non-living substance (inorganic or organic). In particular, biological fouling caused by deposition and then growth of microbes in colonies known as biofilms, is a major challenge. Biofilms are difficult to prevent due to sensitivity of RO membranes to chemical disinfectants and once formed are extremely difficult to eradicate by current chemical cleaning methods. In this project the persistence of biofilms will be used to turn the biofouling problem on its head by engineering biofilms that 1) control their own thickness and 2) release molecules (signals) that prevent colonization of this engineered biofilm by other microorganisms. This biofilm will also be engineered to contribute to the removal of the contaminants that can pass through the RO membrane.The ability to make bacteria dissolve deleterious biofilms by activating a series of genetic pathways (i.e., to secrete enzymes to remove the polymers that cement the bacteria in place and to make the bacteria swim away) has to date not been proposed for RO biofouling control. Therefore, a novel feature of this proposal is the use of metabolic engineering to create the first living membrane comprising RO membranes and a thin beneficial biofilm that will both prevent biofouling as well as remove toxic wastes in water recovery systems. To control the extent of the beneficial biofilm, the PIs will capitalize on the fact that E. coli possesses a novel diguanylate cyclase (c-di-GMP)-binding protein, BdcA. The PIs have engineered BdcA to cause biofilm dispersal. By controlling BdcA production, the extent of biofilm formation by the beneficial biofilm can be limited. The PIs also propose to demonstrate that it is possible to incorporate contaminant degrading enzymes in these beneficial biofilm bacteria to enhance removal of recalcitrant compounds. By controlling biofilms on RO membranes, chemicals required for disinfection and cleaning will be eliminated and the overall power consumption of this critical water treatment technology will be minimized. This work is also important in terms of gaining insights on how to control biofilm formation for engineering applications, and it may provide insights for controlling biofilm formation to treat chronic diseases. For this work, at least two undergraduates/year will be trained with efforts made to recruit underrepresented groups. Research results will be disseminated to a diverse audience using YouTube as professionally-filmed, instructive videos. Finally, the ongoing water science and education camp for middle schoolers, a part of the popular Science U program at Penn State University, will be expanded from a three day program to a week and a new graduate course on membranes will be developed.