Performance of Microbiologically Enhanced Concrete Structural Elements

这项拟议研究的主旨是使用基因工程微生物(GEMS)的新型微生物产品来提高混凝土的性能。要研究的主要微生物产品是胞外聚合物(EPS)，它能促进微生物附着在各种类型的表面结构上。将微生物有机聚合物的选择性胶结性能与我们以前研究中介绍的微生物诱导的无机方解石的胶结性能进行比较。在这项研究中，我们提出了一个雄心勃勃的计划，开发拥有并表达负责生物聚合物生产和方解石沉淀的基因的宝石。随着预算的减少，这项研究的范围已被修订：(1)开发可生产用于混凝土修复的各种生物粘合剂的宝石；(2)在混凝土中以较小的规模应用这些基因工程微生物产品。拟议研究的学术价值是在微生物混凝土增强方面引入新的、先进的和创新的方法，意在不仅仅是继续先前的研究，而是将这一概念提升到一个新的水平。拟议研究的最重要方面是确定可有效用于混凝土修复而不对环境造成任何不利影响的替代生物制品，以及利用正在进行的重组微生物尿素酶研究的初步结果在混凝土修复中使用尖端分子DNA和固定化技术。此外，这项拟议的研究计划包括开发一种可以长期保存微生物密封材料的方法。通过之前由美国国家科学基金会资助的项目(CMS-9802127和INT-0002608)，南达科他州采矿与技术学院的Bang博士(环境微生物学家)和Ramakrishnan博士(土木/混凝土工程师)建立了密切的跨学科研究合作。私人投资机构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在工程上的应用，这是这一提议的基础。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澳大利亚研究团队，澳大利亚珀斯科廷科技大学的J.R.Warmington博士(生物医学科学学院)和B.V.Rangan博士(土木工程学院)。SDSM&amp；T和澳大利亚研究团队之间的这种国际合作为两个校区的专业知识提供了互补的机会，并为这一提议奠定了重要的基础。拟议活动的更广泛影响强调以下两个方面：(1)将申请区域教育联盟的补充资金，以便在校园内和南达科他州邻近的部落大学招收代表人数不足的少数族裔学生。这些本科生将积极参与该项目，帮助研究生进行研究，进一步发展自己的自主研究课题。将鼓励学生参与动手实验、数据分析和汇编、在会议上的陈述和科学论文的准备。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，通过这些机会，学生将获得重要的研究经验，并发展批判性思维技能。(2)对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用于建筑结构缝隙的密封剂或填缝剂，生物修复是指通过选择性胶结来限制受污染的含水层或地下土壤，并可能用于表层土壤的粉尘控制。因此，提出的新方法的重要性和意义不仅在于在混凝土加固中应用的可行性，而且还包括该技术在其他修复领域的进一步适用性。

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.