Performance of Microbiologically Enhanced Concrete Structural Elements

本研究的主旨是利用基因工程微生物（GEMs）的新型微生物产物来提高混凝土的性能。 待研究的主要微生物产物是促进微生物粘附于各种类型的表面结构的胞外聚合物（EPS）。 微生物有机聚合物的选择性胶结性能将与从我们以前的研究中引入的微生物诱导的无机方解石进行比较。 在这项研究中，我们提出了一个雄心勃勃的计划，开发创业板港口和表达基因负责的生物聚合物生产以及方解石沉淀的同时。 随着预算的减少，这项研究的范围已经修改（1）开发生产各种类型的生物密封剂的混凝土修复和（2）在混凝土中应用这些基因工程微生物产品在缩小规模。 拟议研究的智力价值是在微生物混凝土增强中引入新的，先进的和创新的方法，不只是继续以前的研究，而是将这一概念提升到一个新的水平。 拟议的研究的最重要的方面是替代生物产品，可用于混凝土修复有效地没有任何不利影响的环境和使用尖端的分子DNA和固定化技术在混凝土修复，利用正在进行的重组微生物脲酶的研究的初步结果的识别。 此外，这项研究计划还包括开发一种方法，可以保存微生物密封材料的时间延长。通过以前的NSF资助项目（CMS-9802127和INT-0002608），Bang博士（环境微生物学家）和Ramakrishnan博士（土木/混凝土工程师）在南达科他州矿业与技术学院（SDSM T）建立了密切的跨学科研究合作。 PI之间的合作研究工作强调了微生物诱导方解石沉淀的基本概念的工程应用，这是本提案的基础基石。 此外，通过NSF/INT计划目前的资助，我们的研究合作已经扩大到包括一个澳大利亚研究团队，J.R.澳大利亚珀斯科廷科技大学的沃明顿（生物医学科学学院）和B. V. Rangan博士（土木工程学院）。 SDSM T和澳大利亚研究团队之间的这种国际合作提供了一个机会，以补充两个校区的专业知识，并为这一提议奠定了重要基础。 拟议活动的更广泛影响强调以下两个方面：（1）将要求REU补充资金，在校园内和从南达科他州邻近的部落学院招收代表性不足的少数民族学生。 这些本科生将积极参与该项目，协助研究生的研究，并进一步发展自己的独立研究课题。 学生将被鼓励参加动手实验，分析和数据的组装，在会议上介绍，并准备科学论文。 我们的跨学科研究工作也将为本科生和研究生提供独特的机会，通过这些学生将获得重要的研究经验，并培养批判性思维能力。 (2)至于混凝土加固以外的潜在应用，这些无害环境的生物产品可以稍加修改后用作建筑结构间隙的密封剂或填缝剂，通过选择性胶结作用限制受污染含水层或地下土壤的生物修复手段，以及可能的地表土壤粉尘控制。 因此，所提出的新方法的重要性和意义不仅跨越在混凝土增强应用的可行性，但也进一步适用于该技术在其他领域的补救。

The thrust of this proposed research is to enhance the performance of concrete using novel microbial products of genetically engineered microorganisms (GEMs). The prime microbial product to be studied is the extracellular polymeric substance (EPS) that promotes microbes to adhere to various types of the surface structures. Selective cementation properties of the microbial organic polymer will be compared with those of the microbiologically induced inorganic calcite that was introduced from our previous studies. In this study, we propose an ambitious plan to develop GEMs that harbor and express genes responsible for the biopolymer production as well as calcite precipitation simultaneously. With the reduced budget, the scope of this research has been revised (1) to develop GEMs that produce various types of biosealant for concrete remediation and (2) to apply these genetically engineered microbial products in concrete in a reduced scale. The intellectual merit of the proposed study is to introduce new, advanced and innovative approaches in microbial concrete enhancement, intending not to merely continue the previous research, rather elevating this concept to the next level. The most significant aspects of the proposed research are the identification of alternative biological products that can be used for concrete remediation effectively without any adverse impact to environments and the use of cutting-edge molecular DNA and immobilization technology in concrete remediation, utilizing preliminary findings from on-going research on recombinant microbial urease. Further, this proposed research scheme includes the development of a method that can preserve microbial sealing material for an extended period of time.Through previous NSF funded projects (CMS-9802127 and INT-0002608), Dr. Bang (Environmental Microbiologist) and Dr. Ramakrishnan (Civil/Concrete Engineer) at the South Dakota School of Mines and Technology (SDSM&T) have established close interdisciplinary research collaboration. The collaborative research efforts between the PIs have emphasized engineering application of basic concepts of microbiologically induced calcite precipitation, which is the underlying cornerstone of this proposal. In addition, through the current funding from the NSF/INT program, our research collaboration has expanded to include an Australian research team, Dr. J.R. Warmington (School of Biomedical Sciences) and Dr. B.V. Rangan (School of Civil Engineering) of the Curtin University of Technology, Perth, Australia. This international collaboration between SDSM&T and Australian research teams has provided an opportunity to complement two campuses' expertise and laid major groundwork for this proposal. The broader impacts of the proposed activity emphasize the following two aspects: (1) REU supplementary funding will be requested to recruit underrepresented minority students on campus and from adjacent tribal colleges in South Dakota. These undergraduate students will actively participate in the project, assisting graduate students' research and further developing their own independent research topics. Students will be encouraged to participate in hands-on experiments, analysis and assembly of data, presentation at conferences, and preparation of scientific papers. Our interdisciplinary research efforts will also provide unique opportunities to undergraduate and graduate students, through which students will gain significant research experience and develop critical thinking skills. (2) As for potential applications beyond concrete reinforcement, these environmentally innocuous biological products may be utilized with slight modification as sealing or caulking agents for the gaps in building structures, bioremediation means to confine contaminated aquifers or subsurface soils through selective cementation, and possibly dust control for surface soils. Therefore, the importance and significance of the proposed novel approaches span not only the feasibility of application in concrete enhancement but also further applicability of the technique in other areas of remediation.